Grayscale-to-Color: Scalable Fabrication of Custom Multispectral Filter Arrays
- Calum WilliamsCalum WilliamsElectrical Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, U.K.Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, U.K.More by Calum Williams
- George S. D. GordonGeorge S. D. GordonElectrical Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, U.K.More by George S. D. Gordon
- Timothy D. WilkinsonTimothy D. WilkinsonElectrical Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, U.K.More by Timothy D. Wilkinson
- Sarah E. Bohndiek*Sarah E. Bohndiek*E-mail: [email protected].Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, U.K.Cancer Research UK Cambridge Institute, University of Cambridge, Robinson Way, Cambridge, CB2 0RE, U.K.More by Sarah E. Bohndiek
Abstract

Snapshot multispectral image (MSI) sensors have been proposed as a key enabler for a plethora of multispectral imaging applications, from diagnostic medical imaging to remote sensing. With each application requiring a different set, and number, of spectral bands, the absence of a scalable, cost-effective manufacturing solution for custom multispectral filter arrays (MSFAs) has prevented widespread MSI adoption. Despite recent nanophotonic-based efforts, such as plasmonic or high-index metasurface arrays, large-area MSFA manufacturing still consists of many-layer dielectric (Fabry–Perot) stacks, requiring separate complex lithography steps for each spectral band and multiple material compositions for each. It is an expensive, cumbersome, and inflexible undertaking, but yields optimal optical performance. Here, we demonstrate a manufacturing process that enables cost-effective wafer-level fabrication of custom MSFAs in a single lithographic step, maintaining high efficiencies (∼75%) and narrow line widths (∼25 nm) across the visible to near-infrared. By merging grayscale (analog) lithography with metal–insulator–metal (MIM) Fabry–Perot cavities, whereby exposure dose controls cavity thickness, we demonstrate simplified fabrication of MSFAs up to N-wavelength bands. The concept is first proven using low-volume electron beam lithography, followed by the demonstration of large-volume UV mask-based photolithography with MSFAs produced at the wafer level. Our framework provides an attractive alternative to conventional MSFA manufacture and metasurface-based spectral filters by reducing both fabrication complexity and cost of these intricate optical devices, while increasing customizability.
Results and Discussion
Figure 1

Figure 1. Multispectral filter arrays (MSFAs) using grayscale lithography with metal–insulator–metal (MIM) geometry. (a) Schematic: (i) using a customized MSFA atop a monochrome image sensor for multispectral imaging. (ii) 3D MIM structure of MSFA with inset detailing layers. The wavelength transmitted to each pixel below the MIM structures is controlled with the single-step lithographic fabrication process. (b) MSFA fabrication process: (i) a spatially varying grayscale exposure dose results in a spatially varying wavelength transmission profile. (ii) Calculated grayscale exposure dose profile corresponding to remaining resist thickness profiles (“resist sensitivity” curve). An ultrathin noble metal (Ag) layer on glass (SiO2) acts both to dissipate accumulated charge and as the bottom mirror of the filter. (iii) A spatially variant dose modulated exposure leaves a 3D resist profile postdevelopment. (iv) Post-metal-deposition: with a top metal (mirror) layer, the spatially varying 3D resist profile acts to filter the light according to the eigenmode solution of the stack. (v) Final spectral transmittance profiles of MIM structures.
Figure 2

Figure 2. Grayscale exposure dose to color: experimental verification. (a) Finite-difference time-domain (FDTD) simulations of the optical transmission from a continuous Ag-based MIM cavity as a function of varying insulator thickness, with geometry: SiO2(bulk)–Ag(26 nm)–resist (n = 1.653)–Ag(26 nm)–MgF2(12 nm). (b) Experimental demonstration of grayscale-to-dose pattern with the same layers as in (a): (i) Transmission spectra from dose-modulated 5 μm × 5 μm squares (optical micrograph shown in inset), which results in increasing thickness and hence varying peak wavelengths; (ii) measured curve, using an AFM, linking dose and thickness (standard deviation error bars in blue, with overlaid polynomial-fitted red line). Only the first-order resonance is present at low doses, but for higher doses (>50 μC cm–2), the second-order mode is also excited. (c) Dose-modulated 5 μm × 5 μm pixel array with 10 μm spacing: (i) dose-modulated pattern, (ii) optical micrograph, and (iii) corresponding AFM data. (d) Same as (c) but with zero dead space.
Figure 3

Figure 3. Demonstration of the versatility of grayscale MSFAs through patterned design variety. (a) Optical micrograph (with magnified inset) of the University of Cambridge logo text composed of 10 μm pixels with a randomized exposure dose profile, hence random colors in transmission. (b) RGB+NIR MSFA (bands labeled in inset) with (i) optical micrograph in transmission and (ii) respective transmission spectra of the wavelength bands. (c) Photograph of three identically processed chips with a range of patterned designs on each chip with varying complexity. Each chip is processed in a single lithographic step in G-EBL. (d) Spectrally “ordered” 4 × 3 mosaic: (i) optical micrograph; (ii) transmission spectra. (e) 25 μm linearly variable filter pixel design: (i) optical micrograph; (ii) AFM micrograph of the unit cell showing the in-plane height variation. (f) Optical micrograph (with magnified inset) of an array of RGB pixels with exponentially (2–n) decreasing pixel width, starting from 10 μm. (g) 25 μm discrete spiral phase pixel design: (i) optical micrograph; (ii) AFM micrograph. Transmission spectra represent averages of five different acquisitions, taken at random positions across the array.
Figure 4

Figure 4. Multispectral imaging through a Bayer filter design and 9-band (3 × 3) MSFA. Bayer filter: (a) Optical micrograph of the mosaic with respective transmission spectra (b) of the 3 bands (RGB). (c) Imaging: Physical representation of the MSFA in front of the image sensor: experimental AFM micrograph, optical micrograph, and image sensor schematic, where d is the distance of the MSFA from the sensor plane (∼1 mm). The experimental imaging setup is shown in SI Figure S16. (d) A snapshot of the imaging test scene, including Macbeth ColorChecker chart and Rubik’s cube, captured with a monochrome image sensor through our mosaic (top) and using a conventional smartphone (bottom), for reference. Aside from demosaicing, there is no postprocessing (enhancement) of the color in the image acquired through our mosaic. 3 × 3 MSFA: (e) Optical micrograph of the 3 × 3 mosaic with respective transmission spectra (f) of the 9 bands (labeled) in the MSFA. (g) Multispectral imaging: Schematic representation of the MSFA in front of the image sensor: experimental AFM micrograph, optical micrograph, and image sensor schematic, where d is the distance of the MSFA from the sensor plane (∼1 mm). 2D intensity matrices from the monochrome image sensor (captured through the MSFA) with illumination from a supercontinuum source are shown in SI Section S 3.3 and SI Video S1 at four different center wavelengths: 500, 550, 600, 650 nm; fwhm 10 ± 2 nm. (h) Multispectral test scene comprising a rear-illuminated filter wheel with four different bandpass filters. (Top) “Raw” color image captured using the monochrome image sensor through our MSFA with individual MSFA pixels visible. (Bottom) Reference image of test scene (comprising 4 bandpass filters across the visible spectrum) taken using a conventional smartphone image sensor. (i) Demosaiced color-coded images for four different wavelength bands obtained from the “raw” image in (h) (top), with labels denoting band.
Figure 5

Figure 5. Wafer-scale grayscale-to-color MSFA fabrication. Photolithography-based MSFA fabrication process flow schematic comparing two proposed approaches: a grayscale photomask (a) or binary photomask (b); both result in equivalent MSFAs. (a) (i) 3 × 3 grayscale photomask: 9 levels of optical transmission, one per spectral band. A single flood exposure can be performed imparting a spatially varying dose profile into the photoresist (ii). (b) (i) 3 × 3 binary photomask: A single transparent pixel is repeated in a 3 × 3 array (MSFA unit cell). The mask is translated in-plane for each spectral pixel, with varying exposure levels (ii–iv). Once processed, the spectral response of the final MSFA (v) is identical to that from (a). (c) Photograph of a 3 in. wafer with ∼32 9-band MSFAs (utilizing second-order resonances), with a zoomed-in region captured with a macro lens (d) and tiled SEM micrograph (e) of the same region. (f) Optical micrograph (transmission) of a different region of the wafer, with labeled equivalent exposure pattern (inset) and corresponding transmission spectra (g) for each spectral band. (h) Photograph of two 3 in. MSFA wafers (utilizing first- and second-order resonances), with optical micrograph of one MSFA (i) and its corresponding transmission spectra for each band (j).
Conclusion
Methods
Fabrication Techniques
EBL Processing
PL Processing
Optical and Morphological Characterizations
Numerical Simulations
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsphotonics.9b01196.
Simulations of transmission and angle dependency; fabrication process optimization and materials considerations (PDF)
Movie illustrating MSFA characterization (AVI)
C.W. conceived the idea. C.W. carried out the design and simulation of the devices. C.W. fabricated the devices and performed the experimental measurements. C.W. characterized the devices. G.S.D.G., T.D.W., and S.E.B. supervised the study. C.W., G.S.D.G., T.D.W., and S.E.B. analyzed the data and wrote the manuscript.
The authors declare no competing financial interest.
Please note that the dataset to accompany this manuscript will be posted at: https://doi.org/10.17863/CAM.45120 before publication.
Terms & Conditions
Electronic Supporting Information files are available without a subscription to ACS Web Editions. The American Chemical Society holds a copyright ownership interest in any copyrightable Supporting Information. Files available from the ACS website may be downloaded for personal use only. Users are not otherwise permitted to reproduce, republish, redistribute, or sell any Supporting Information from the ACS website, either in whole or in part, in either machine-readable form or any other form without permission from the American Chemical Society. For permission to reproduce, republish and redistribute this material, requesters must process their own requests via the RightsLink permission system. Information about how to use the RightsLink permission system can be found at http://pubs.acs.org/page/copyright/permissions.html.
Acknowledgments
This work was supported by Cancer Research UK (C55962/A24669, C47594/A21102, C14303/A17197, C47594/A16267) and the Engineering and Physical Sciences Research Council (EP/R003599/1). C.W. would like to acknowledge the support of Wolfson College, Cambridge. The authors would like to acknowledge the following researchers for their fruitful discussions and help with the work: Sophia Gruber, Catherine Fitzpatrick, Girish Rughoobur, Dale Waterhouse, Jonghee Yoon, Siri Luthman, and Christian Kuppe.
References
This article references 40 other publications.
- 1Kuroda, T. Essential Principles of Image Sensors; CRC Press, 2017.
- 2Lu, G.; Fei, B. Medical Hyperspectral Imaging: A Review. J. Biomed. Opt. 2014, 19 (1), 010901 DOI: 10.1117/1.JBO.19.1.010901[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVKms7rF&md5=00c5cb61bbe4e24944cc5e199e94ef0bMedical hyperspectral imaging: a reviewLu, Guolan; Fei, BaoweiJournal of Biomedical Optics (2014), 19 (1), 010901/1-010901/23CODEN: JBOPFO; ISSN:1083-3668. (Society of Photo-Optical Instrumentation Engineers)A review. Hyperspectral imaging (HSI) is an emerging imaging modality for medical applications, esp. in disease diagnosis and image-guided surgery. HSI acquires a three-dimensional dataset called hypercube, with two spatial dimensions and one spectral dimension. Spatially resolved spectral imaging obtained by HSI provides diagnostic information about the tissue physiol., morphol., and compn. This review paper presents an overview of the literature on medical hyperspectral imaging technol. and its applications. The aim of the survey is threefold: an introduction for those new to the field, an overview for those working in the field, and a ref. for those searching for literature on a specific application.
- 3Lapray, P. J.; Wang, X.; Thomas, J. B.; Gouton, P. Multispectral Filter Arrays: Recent Advances and Practical Implementation. Sensors 2014, 14 (11), 21626– 21659, DOI: 10.3390/s141121626[Crossref], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2M3psFynsQ%253D%253D&md5=ba13ebbb41eab04bae2d9acf695fe2d5Multispectral filter arrays: recent advances and practical implementationLapray Pierre-Jean; Wang Xingbo; Thomas Jean-Baptiste; Gouton PierreSensors (Basel, Switzerland) (2014), 14 (11), 21626-59 ISSN:.Thanks to some technical progress in interferencefilter design based on different technologies, we can finally successfully implement the concept of multispectral filter array-based sensors. This article provides the relevant state-of-the-art for multispectral imaging systems and presents the characteristics of the elements of our multispectral sensor as a case study. The spectral characteristics are based on two different spatial arrangements that distribute eight different bandpass filters in the visible and near-infrared area of the spectrum. We demonstrate that the system is viable and evaluate its performance through sensor spectral simulation.
- 4Bayer, B. E. Color Imaging Array. US3971065A, 1975.Google ScholarThere is no corresponding record for this reference.
- 5Geelen, B.; Tack, N.; Lambrechts, A. A Compact Snapshot Multispectral Imager with a Monolithically Integrated Per-Pixel Filter Mosaic. Proc. SPIE 2014, 8974, 89740L DOI: 10.1117/12.2037607 .
- 6Hagen, N.; Kudenov, M. W. Review of Snapshot Spectral Imaging Technologies. Opt. Eng. 2013, 52 (9), 090901 DOI: 10.1117/1.OE.52.9.090901 .
- 7Coffey, V. C. Multispectral Imaging Moves into the Mainstream. Opt. Photonics News 2012, 23 (4), 18– 24, DOI: 10.1364/OPN.23.4.000018
- 8Carmo, J. P.; Rocha, R. P.; Bartek, M.; De Graaf, G.; Wolffenbuttel, R. F.; Correia, J. H. A Review of Visible-Range Fabry-Perot Microspectrometers in Silicon for the Industry. Opt. Laser Technol. 2012, 44 (7), 2312– 2320, DOI: 10.1016/j.optlastec.2012.03.036[Crossref], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xnsl2lsb0%253D&md5=f598de404f8d3fbad966fbc8e3be23f5A review of visible-range Fabry-Perot microspectrometers in silicon for the industryCarmo, Joao Paulo; Rocha, Rui Pedro; Bartek, Marian; de Graaf, Ger; Wolffenbuttel, Reinoud F.; Correia, Jose HiginoOptics & Laser Technology (2012), 44 (7), 2312-2320CODEN: OLTCAS; ISSN:0030-3992. (Elsevier Ltd.)This review presents microspectrometers in silicon for the industry for measuring light in the visible range, using the Fabry-Perot interferometric technique. The microspectrometers are devices able to do the anal. of the individual spectral components in a given signal and are extensively used on spectroscopy. The anal. of the interaction between the matter and the radiated energy can found huge applications in the industrial sector. The microspectrometers can be divided on three types, detd. by the dispersion element or the used approach and can be found microspectrometers based on prisms, gratings interferometers. Both types of microspectrometers can be used to analyze the spectral content ranging from the UV (<390 nm), passing into the visible region of the electromagnetic spectrum (VIS, 390-760 nm) up to the IR (>760 nm). The microspectrometers in silicon are versatile microinstruments because silicon-compatible techniques can be used to assembly both the optical components with the readout and control electronics, thus resulting high-vol. with high-reproducibility and low-cost batch fabrications. A compensation technique for minimizing the scattered light effects on interferometers was implemented and is also a contribution of this paper. Fabry-Perot microspectrometers for the visible range are discussed in depth for use in industrial applications.
- 9Dillon, P. L. P.; Brault, A. T.; Horak, J. R.; Garcia, E.; Martin, T. W.; Light, W. A. Fabrication and Performance of Color Filter Arrays for Solid- State Imagers. IEEE Trans. Electron Devices 1978, 25, 97 DOI: 10.1109/T-ED.1978.19045 .
- 10Chen, Q.; Hu, X.; Wen, L.; Yu, Y.; Cumming, D. R. S. Nanophotonic Image Sensors. Small 2016, 12 (36), 4922– 4935, DOI: 10.1002/smll.201600528[Crossref], [PubMed], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XovVamt7o%253D&md5=53ac33f2a0c097f1cea9864e0cb708feNanophotonic Image SensorsChen, Qin; Hu, Xin; Wen, Long; Yu, Yan; Cumming, David R. S.Small (2016), 12 (36), 4922-4935CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)The increasing miniaturization and resoln. of image sensors bring challenges to conventional optical elements such as spectral filters and polarizers, the properties of which are detd. mainly by the materials used, including dye polymers. Recent developments in spectral filtering and optical manipulating techniques based on nanophotonics have opened up the possibility of an alternative method to control light spectrally and spatially. By integrating these technologies into image sensors, it will become possible to achieve high compactness, improved process compatibility, robust stability and tunable functionality. In this Review, recent representative achievements on nanophotonic image sensors are presented and analyzed including image sensors with nanophotonic color filters and polarizers, metamaterial-based THz image sensors, filter-free nanowire image sensors and nanostructured-based multispectral image sensors. This novel combination of cutting edge photonics research and well-developed com. products may not only lead to an important application of nanophotonics but also offer great potential for next generation image sensors beyond Moore's Law expectations.
- 11Macleod, H. Thin-Film Optical Filters, third ed.; Institute of Physics Publishing, 1986.
- 12Kristensen, A.; Yang, J. K. W.; Bozhevolnyi, S. I.; Link, S.; Nordlander, P.; Halas, N. J.; Mortensen, N. A. Plasmonic Colour Generation. Nat. Rev. Mater. 2017, 2 (1), 1– 15, DOI: 10.1038/natrevmats.2016.88
- 13Shah, Y. D.; Grant, J.; Hao, D.; Kenney, M.; Pusino, V.; Cumming, D. R. S. Ultra-Narrow Line Width Polarization-Insensitive Filter Using a Symmetry-Breaking Selective Plasmonic Metasurface. ACS Photonics 2018, 5 (2), 663– 669, DOI: 10.1021/acsphotonics.7b01011[ACS Full Text
], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGgurrK&md5=9ad2b9f20923e9f4b907ba3aa5eab991Ultra-narrow Line Width Polarization-Insensitive Filter Using a Symmetry-Breaking Selective Plasmonic MetasurfaceShah, Yash D.; Grant, James; Hao, Danni; Kenney, Mitchell; Pusino, Vincenzo; Cumming, David R. S.ACS Photonics (2018), 5 (2), 663-669CODEN: APCHD5; ISSN:2330-4022. (American Chemical Society)Plasmonic metasurfaces provide unprecedented control of the properties of light. By designing symmetry-breaking nanoholes in a metal sheet and engineering the optical properties of the metal using geometry, highly selective transmission and polarization control of light is obtained. To date such plasmonic filters have exhibited broad (>200 nm) transmission line widths in the NIR and as such are unsuitable for applications requiring narrow passbands, e.g., multispectral imaging. A novel subwavelength elliptical and circular nanohole array in a metallic film that simultaneously exhibits high transmission efficiency, polarization insensitivity, and narrow line width is presented. The exptl. obtained line width is 79 nm with a transmission efficiency of 44%. By examg. the elec. and magnetic field distributions for various incident polarizations at the transmission peak the narrowband characteristics are due to a Fano resonance. Agreement is obtained between the exptl. data, simulations, and anal. calcns. The design can be modified to operate in other regions of the electromagnetic spectrum, and these filters may be integrated with suitable detectors such as photodiodes and single-photon avalanche diode arrays. - 14Williams, C.; Rughoobur, G.; Flewitt, A. J.; Wilkinson, T. D. Nanostructured Plasmonic Metapixels. Sci. Rep. 2017, 7 (1), 7745, DOI: 10.1038/s41598-017-08145-0[Crossref], [PubMed], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC1cfms1SnsQ%253D%253D&md5=2f7acb33e3907077a48bc34c3a26dec2Nanostructured plasmonic metapixelsWilliams Calum; Wilkinson Timothy D; Rughoobur Girish; Flewitt Andrew JScientific reports (2017), 7 (1), 7745 ISSN:.State-of-the-art pixels for high-resolution microdisplays utilize reflective surfaces on top of electrical backplanes. Each pixel is a single fixed color and will usually only modulate the amplitude of light. With the rise of nanophotonics, a pixel's relatively large surface area (~10 μm(2)), is in effect underutilized. Considering the unique optical phenomena associated with plasmonic nanostructures, the scope for use in reflective pixel technology for increased functionality is vast. Yet in general, low reflectance due to plasmonic losses, and sub-optimal design schemes, have limited the real-world application. Here we demonstrate the plasmonic metapixel; which permits high reflection capability whilst providing vivid, polarization switchable, wide color gamut filtering. Ultra-thin nanostructured metal-insulator-metal geometries result in the excitation of hybridized absorption modes across the visible spectrum. These modes include surface plasmons and quasi-guided modes, and by tailoring the absorption modes to exist either side of target wavelengths, we achieve pixels with polarization dependent multicolor reflection on mirror-like surfaces. Because the target wavelength is not part of a plasmonic process, subtractive color filtering and mirror-like reflection occurs. We demonstrate wide color-range pixels, RGB pixel designs, and in-plane Gaussian profile pixels that have the potential to enable new functionality beyond that of a conventional 'square' pixel.
- 15Kumar, K.; Duan, H.; Hegde, R. S.; Koh, S. C. W.; Wei, J. N.; Yang, J. K. W. Printing Colour at the Optical Diffraction Limit. Nat. Nanotechnol. 2012, 7 (9), 557– 561, DOI: 10.1038/nnano.2012.128[Crossref], [PubMed], [CAS], Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFOgsbzL&md5=f52d4449163bb4ba854d0cf90ea2acfbPrinting color at the optical diffraction limitKumar, Karthik; Duan, Huigao; Hegde, Ravi S.; Koh, Samuel C. W.; Wei, Jennifer N.; Yang, Joel K. W.Nature Nanotechnology (2012), 7 (9), 557-561CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)The highest possible resoln. for printed color images is detd. by the diffraction limit of visible light. To achieve this limit, individual color elements (or pixels) with a pitch of 250 nm are required, translating into printed images at a resoln. of ∼100,000 dots per in. (d.p.i.). However, methods for dispensing multiple colorants or fabricating structural color through plasmonic structures have insufficient resoln. and limited scalability. Here, we present a non-colorant method that achieves bright-field color prints with resoln. up to the optical diffraction limit. Color information is encoded in the dimensional parameters of metal nanostructures, so that tuning their plasmon resonance dets. the colors of the individual pixels. Our color-mapping strategy produces images with both sharp color changes and fine tonal variations, is amenable to large-vol. color printing via nanoimprint lithog., and could be useful in making micro-images for security, steganog., nanoscale optical filters and high-d. spectrally encoded optical data storage.
- 16Burgos, S. P.; Yokogawa, S.; Atwater, H. A. Color Imaging via Nearest Neighbor Hole Coupling in Plasmonic Color Filters Integrated onto a Complementary Metal-Oxide Semiconductor Image Sensor. ACS Nano 2013, 7 (11), 10038– 10047, DOI: 10.1021/nn403991d[ACS Full Text
], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs1Oku77I&md5=a8fb50006f555fe474696093dcaeaff1Color imaging via nearest neighbor hole coupling in plasmonic color filters integrated onto a complementary metal-oxide semiconductor image sensorBurgos, Stanley P.; Yokogawa, Sozo; Atwater, Harry A.ACS Nano (2013), 7 (11), 10038-10047CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)State-of-the-art CMOS imagers are composed of very small pixels, so it is crit. for plasmonic imaging to understand the optical response of finite-size hole arrays and their coupling efficiency to CMOS image sensor pixels. Here, the authors demonstrate that the transmission spectra of finite-size hole arrays can be accurately described by only accounting for up to the second nearest-neighbor scattering-absorption interactions of hole pairs, thus making hole arrays appealing for close-packed color filters for imaging applications. Using this model, they find that the peak transmission efficiency of a square-shaped hole array with a triangular lattice reaches ∼90% that of an infinite array at an extent of ∼6 × 6 μm2, the smallest size array showing near-infinite array transmission properties. Finally, they exptl. validate their findings by investigating the transmission and imaging characteristics of a 360 × 320 pixel plasmonic color filter array composed of 5.6 × 5.6 μm2 RGB color filters integrated onto a com. black and white 1/2.8 in. CMOS image sensor, demonstrating full-color high resoln. plasmonic imaging. Their results show good color fidelity with a 6-color-averaged color difference metric (ΔE) in the range of 16.6-19.3, after white balancing and color-matrix correcting raw images taken with f-nos. ranging from 1.8 to 16. The integrated peak filter transmission efficiencies are measured to be in the 50% range, with a FWHM of 200 nm for all three RGB filters, in good agreement with the spectral response of isolated unmounted color filters. - 17Shaltout, A. M.; Kim, J.; Boltasseva, A.; Shalaev, V. M.; Kildishev, A. V. Ultrathin and Multicolour Optical Cavities with Embedded Metasurfaces. Nat. Commun. 2018, 9 (1), 1– 7, DOI: 10.1038/s41467-018-05034-6[Crossref], [PubMed], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtlSlurnL&md5=089b9cd25476f353e67a0ec22bc17e81Ultrathin and multicolour optical cavities with embedded metasurfacesShaltout, Amr M.; Kim, Jongbum; Boltasseva, Alexandra; Shalaev, Vladimir M.; Kildishev, Alexander V.Nature Communications (2018), 9 (1), 1-7CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)Over the past years, photonic metasurfaces have demonstrated their remarkable and diverse capabilities in advanced control over light propagation. Here, we demonstrate that these artificial films of deeply subwavelength thickness also offer new unparalleled capabilities in decreasing the overall dimensions of integrated optical systems. We propose an original approach of embedding a metasurface inside an optical cavity-one of the most fundamental optical elements-to drastically scale-down its thickness. By modifying the Fabry-Pe´rot interferometric principle, this methodol. is shown to reduce the metasurface-based nanocavity thickness below the conventional λ/(2n) min. In addn., the nanocavities with embedded metasurfaces can support independently tunable resonances at multiple bands. As a proof-of-concept, using nanostructured metasurfaces within 100-nm nanocavities, we exptl. demonstrate high spatial resoln. color filtering and spectral imaging. The proposed approach can be extrapolated to compact integrated optical systems on-a-chip such as VCSEL's, high-resoln. spatial light modulators, imaging spectroscopy systems, and bio-sensors.
- 18Davis, M. S.; Zhu, W.; Xu, T.; Lee, J. K.; Lezec, H. J.; Agrawal, A. Aperiodic Nanoplasmonic Devices for Directional Colour Filtering and Sensing. Nat. Commun. 2017, 8 (1), DOI: 10.1038/s41467-017-01268-y .
- 19Yokogawa, S.; Burgos, S. P.; Atwater, H. A. Plasmonic Color Filters for CMOS Image Sensor Applications. Nano Lett. 2012, 12 (8), 4349– 4354, DOI: 10.1021/nl302110z[ACS Full Text
], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVejtbjJ&md5=0cb1613783d0b1dc386168673aa5a552Plasmonic Color Filters for CMOS Image Sensor ApplicationsYokogawa, Sozo; Burgos, Stanley P.; Atwater, Harry A.Nano Letters (2012), 12 (8), 4349-4354CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)We report on the optical properties of plasmonic hole arrays as they apply to requirements for plasmonic color filters designed for state-of-the-art Si CMOS image sensors. The hole arrays are composed of hexagonally packed subwavelength sized holes on a 150 nm Al film designed to operate at the primary colors of red, green, and blue. Hole array plasmonic filters show peak transmission in the 40-50% range for large (>5 × 5 μm2) size filters and maintain their filtering function for pixel sizes as small as ∼1 × 1 μm2, albeit at a cost in transmission efficiency. Hole array filters are found to robust with respect to spatial crosstalk between pixel within our detection limit and preserve their filtering function in arrays contg. random defects. Anal. of hole array filter transmittance and crosstalk suggests that nearest neighbor hole-hole interactions rather than long-range interactions play the dominant role in the transmission properties of plasmonic hole array filters. We verify this via a simple nearest neighbor model that correctly predicts the hole array transmission efficiency as a function of the no. of holes. - 20Franklin, D.; Chen, Y.; Vazquez-Guardado, A.; Modak, S.; Boroumand, J.; Xu, D.; Wu, S. T.; Chanda, D. Polarization-Independent Actively Tunable Colour Generation on Imprinted Plasmonic Surfaces. Nat. Commun. 2015, 6, 1– 8, DOI: 10.1038/ncomms8337
- 21James, T. D.; Mulvaney, P.; Roberts, A. The Plasmonic Pixel: Large Area, Wide Gamut Color Reproduction Using Aluminum Nanostructures. Nano Lett. 2016, 16 (6), 3817– 3823, DOI: 10.1021/acs.nanolett.6b01250[ACS Full Text
], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XnslCktr4%253D&md5=75abe542d001fd89de1c0e290a2c2afdThe Plasmonic Pixel: Large Area, Wide Gamut Color Reproduction Using Aluminum NanostructuresJames, Timothy D.; Mulvaney, Paul; Roberts, AnnNano Letters (2016), 16 (6), 3817-3823CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)We demonstrate a new plasmonic pixel (PP) design that produces a full-color optical response over macroscopic dimensions. The pixel design employs arrays of aluminum nanorods "floating" above their Babinet complementary screen, Concepts from conventional cyan magenta yellow key (CMYK) printing techniques and red green blue (RGB) digital displays are integrated with nanophotonic design principles and adapted to the prodn. of PP elements. The fundamental PP color blocks of CMYK are implemented via a composite plasmonic nanoantenna/slot design and then mixed in a digital display analog 3 × 3 array to produce a broad-gamut PP. The PP goes beyond current investigations into plasmonic color prodn. by enabling a broad color gamut and phys. large plasmonic color features/devices/images. The use of nanorods also leads to a color response that is polarization tunable. Furthermore, devices are fabricated using aluminum and the fabrication strategy is compatible with inexpensive, rapid-throughput, nanoimprint approaches. Here we quantify, both computationally and exptl., the performance of the PP. Spectral data from a test palette is obtained and a large area (>1.5 cm lateral dimensions) reprodn. of a photograph is generated exemplifying the technique. - 22Jahani, S.; Jacob, Z. All-Dielectric Metamaterials. Nat. Nanotechnol. 2016, 11 (1), 23– 36, DOI: 10.1038/nnano.2015.304[Crossref], [PubMed], [CAS], Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XjslGqtQ%253D%253D&md5=31e733bf7637c01b93600c57f2476e4aAll-dielectric metamaterialsJahani, Saman; Jacob, ZubinNature Nanotechnology (2016), 11 (1), 23-36CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)A review. The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the elec. and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielec. nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), resp., but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there was a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all 4 quadrants of possible permittivities and permeabilities were achieved using completely transparent and high-refractive-index dielec. building blocks. An emerging class of all-dielec. metamaterials consisting of anisotropic crystals was shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. A broad outline is presented of the whole range of electromagnetic effects obsd. using all-dielec. metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Current challenges and future goals for the field at the intersection with quantum, thermal and Si photonics, as well as biomimetic metasurfaces are discussed.
- 23Genevet, P.; Capasso, F.; Aieta, F.; Khorasaninejad, M.; Devlin, R. Recent Advances in Planar Optics: From Plasmonic to Dielectric Metasurfaces. Optica 2017, 4 (1), 139, DOI: 10.1364/OPTICA.4.000139[Crossref], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXjsFGisLw%253D&md5=c20386207d233de3861bbb9eb4fb9c44Recent advances in planar optics: from plasmonic to dielectric metasurfacesGenevet, Patrice; Capasso, Federico; Aieta, Francesco; Khorasaninejad, Mohammadreza; Devlin, RobertOptica (2017), 4 (1), 139-152CODEN: OPTIC8; ISSN:2334-2536. (Optical Society of America)This article reviews recent progress leading to the realization of planar optical components made of a single layer of phase shifting nanostructures. After introducing the principles of planar optics and discussing earlier works on subwavelength diffractive optics, we introduce a classification of metasurfaces based on their different phase mechanisms and profiles and a comparison between plasmonic and dielec. metasurfaces. We place particular emphasis on the recent developments on elec. and magnetic field control of light with dielec. nanostructures and highlight the phys. mechanisms and designs required for efficient all-dielec. metasurfaces. Practical devices of general interest such as metalenses, beam deflectors, holograms, and polarizing interfaces are discussed, including high-performance metalenses at visible wavelengths. Successful strategies to achieve achromatic response at selected wavelengths and near unity transmission/reflection efficiency are discussed. Dielec. metasurfaces and dispersion management at interfaces open up technol. opportunities for applications including wavefront control, lightwt. imaging systems, displays, electronic consumer products, and conformable and wearable optics.
- 24Wang, P.; Menon, R. Ultra-High-Sensitivity Color Imaging via a Transparent Diffractive-Filter Array and Computational Optics. Optica 2015, 2 (11), 933, DOI: 10.1364/OPTICA.2.000933
- 25Kats, M. A.; Blanchard, R.; Genevet, P.; Capasso, F. Nanometre Optical Coatings Based on Strong Interference Effects in Highly Absorbing Media. Nat. Mater. 2013, 12 (1), 20– 24, DOI: 10.1038/nmat3443[Crossref], [PubMed], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsV2rsL7F&md5=ee0129e1f718ae1449857ebc355ac65eNanometre optical coatings based on strong interference effects in highly absorbing mediaKats, Mikhail A.; Blanchard, Romain; Genevet, Patrice; Capasso, FedericoNature Materials (2013), 12 (1), 20-24CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Optical coatings, which consist of ≥1 films of dielec. or metallic materials, are widely used in applications ranging from mirrors to eyeglasses and photog. lenses. Many conventional dielec. coatings rely on Fabry-Perot-type interference, involving multiple optical passes through transparent layers with thicknesses of the order of the wavelength to achieve functionalities such as anti-reflection, high-reflection and dichroism. Highly absorbing dielecs. are typically not used because it is generally accepted that light propagation through such media destroys interference effects. Under appropriate conditions interference can instead persist in ultrathin, highly absorbing films of a few to tens of nanometers in thickness, and demonstrate a new type of optical coating comprising such a film on a metallic substrate, which selectively absorbs various frequency ranges of the incident light. These coatings have a low sensitivity to the angle of incidence and require minimal amts. of absorbing material that can be as thin as 5-20 nm for visible light. This technol. has the potential for a variety of applications from ultrathin photodetectors and solar cells to optical filters, to labeling, and even the visual arts and jewellery.
- 26Li, Z.; Butun, S.; Aydin, K. Large-Area, Lithography-Free Super Absorbers and Color Filters at Visible Frequencies Using Ultrathin Metallic Films. ACS Photonics 2015, 2 (2), 183– 188, DOI: 10.1021/ph500410u[ACS Full Text
], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslent7k%253D&md5=525fb0459545ac29f3b9e286cf9c0d9dLarge-Area, Lithography-Free Super Absorbers and Color Filters at Visible Frequencies Using Ultrathin Metallic FilmsLi, Zhongyang; Butun, Serkan; Aydin, KorayACS Photonics (2015), 2 (2), 183-188CODEN: APCHD5; ISSN:2330-4022. (American Chemical Society)Nanostructured photonic materials enable control and manipulation of light at subwavelength scales and exhibit unique optical functionalities. In particular, plasmonic materials and metamaterials have been widely utilized to achieve spectral transmission, reflection, and absorption filters based on localized or delocalized resonances arising from the interaction of photons with nanostructured materials. Realization of visible-frequency, high-performance, large-area, optical filters based on nanoplasmonic materials is rather challenging due to nanofabrication related problems (cost, fabrication imperfection, surface roughness) and optical losses of metals. Here, we propose and demonstrate large-area perfect absorbers and transmission filters that overcome difficulties assocd. with the nanofabrication using a lithog.-free approach. We also utilize and benefit from the optical losses in metals in our optical filter designs. Our resonant optical filter design is based on a modified, asym. metal-insulator-metal (MIM) based Fabry-Perot cavity with plasmonic, lossy ultrathin (∼30 nm) metallic films used as the top metallic layer. We demonstrated a narrow bandwidth (∼17 nm) super absorber with 97% max. absorption with a performance comparable to nanostructure/nanoparticle-based super absorbers. We also investigated transmission (color) filters using ultrathin metallic films, in which different colors can be obtained by controlling the dielec. spacer thickness. With performance parameters of transmittance peak intensity reaching 60% and a narrow-band of ∼40 nm, our color filters exceed the performance of widely studied plasmonic nanohole array based color filters. Proposed asym. Fabry-Perot cavities using ultrathin metallic films could find applications in spectrally selective optical (color and absorber) filters, optoelectronic devices with controlled bandwidth such as narrow-band photodetectors, and light-emitting devices. - 27Kajtár, G.; Kafesaki, M.; Economou, E. N.; Soukoulis, C. M. Theoretical Model of Homogeneous Metal-Insulator-Metal Perfect Multi-Band Absorbers for the Visible Spectrum. J. Phys. D: Appl. Phys. 2016, 49 (5), 55104, DOI: 10.1088/0022-3727/49/5/055104[Crossref], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlyitbjP&md5=958a1061499b620aa05f0afc08dc5edfTheoretical model of homogeneous metal-insulator-metal perfect multi-band absorbers for the visible spectrumKajtar, G.; Kafesaki, M.; Economou, E. N.; Soukoulis, C. M.Journal of Physics D: Applied Physics (2016), 49 (5), 055104/1-055104/6CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)We present a rigorous study of the perfect absorption properties of metal-insulator-metal (MIM) structures in the visible spectrum. We provide a derivation (based on the transfer matrix method) and anal. of the conditions for which the perfect absorption occurs. We show that these conditions are fulfilled when the incident wave excites the eigenmodes of the structure. The quant. anal. allows us to design specific perfect absorbers for our needs. The anal. model is verified by rigorous simulations based on rigorous coupled wave anal., which demonstrate also the angle and polarization insensitivity of the absorption properties of such a structure. Employing the MIM approach and results, we also investigate and demonstrate multiple perfect absorption bands and broad-band absorption in properly designed multilayer metal-insulator systems.
- 28Diest, K.; Dionne, J.; Spain, M. Tunable Color Filters Based on Metal– Insulator– Metal Resonators. Nano Lett. 2009, 9 (7), 2579– 2583, DOI: 10.1021/nl900755b[ACS Full Text
], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXnt1Wrsr8%253D&md5=961e5220803c39daf6a1509a236d09c4Tunable Color Filters Based on Metal-Insulator-Metal ResonatorsDiest, Kenneth; Dionne, Jennifer A.; Spain, Merrielle; Atwater, Harry A.Nano Letters (2009), 9 (7), 2579-2583CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)We report a method for filtering white light into individual colors using metal-insulator-metal resonators. The resonators are designed to support photonic modes at visible frequencies, and dispersion relations are developed for realistic exptl. configurations. Exptl. results indicate that passive Ag/Si3N4/Au resonators exhibit color filtering across the entire visible spectrum. Full field electromagnetic simulations were performed on active resonators for which the resonator length was varied from 1-3 μm and the output slit depth was systematically varied throughout the thickness of the dielec. layer. These resonators are shown to filter colors based on interference between the optical modes within the dielec. layer. By careful design of the output coupling, the resonator can selectively couple to intensity maxima of different photonic modes and, as a result, preferentially select any of the primary colors. We also illustrate how refractive index modulation in metal-insulator-metal resonators can yield actively tunable color filters. Simulations using lithium niobate as the dielec. layer and the top and bottom Ag layers as electrodes, indicate that the output color can be tuned over the visible spectrum with an applied field. - 29Williams, C.; Rughoobur, G.; Flewitt, A. J.; Wilkinson, T. D. Single-Step Fabrication of Thin-Film Linear Variable Bandpass Filters Based on Metal–Insulator–Metal Geometry. Appl. Opt. 2016, 55 (32), 9237, DOI: 10.1364/AO.55.009237[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXkvVSmtro%253D&md5=2dd553cbbddfffbeebafbeb7b1725c35Single-step fabrication of thin-film linear variable bandpass filters based on metal-insulator-metal geometryWilliams, Calum; Rughoobur, Girish; Flewitt, Andrew J.; Wilkinson, Timothy D.Applied Optics (2016), 55 (32), 9237-9241CODEN: APOPAI; ISSN:1559-128X. (Optical Society of America)A single-step fabrication method is presented for ultra-thin, linearly variable optical bandpass filters (LVBFs) based on a metal-insulator-metal arrangement using modified evapn. deposition techniques. This alternate process methodol. offers reduced complexity and cost in comparison to conventional techniques for fabricating LVBFs. We are able to achieve linear variation of insulator thickness across a sample, by adjusting the geometrical parameters of a typical phys. vapor deposition process. We demonstrate LVBFs with spectral selectivity from 400 to 850 nm based on Ag (25 nm) and MgF2 (75-250 nm). Maximum spectral transmittance is measured at ∼70% with a Q-factor of ∼20.
- 30Grant, J.; Kenney, M.; Shah, Y. D.; Escorcia-Carranza, I.; Cumming, D. R. S. CMOS Compatible Metamaterial Absorbers for Hyperspectral Medium Wave Infrared Imaging and Sensing Applications. Opt. Express 2018, 26 (8), 10408, DOI: 10.1364/OE.26.010408[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlKhtbvP&md5=aff14f348ca12713d98b4a7e77beecb6CMOS compatible metamaterial absorbers for hyperspectral medium wave infrared imaging and sensing applicationsGrant, James; Kenney, Mitchell; Shah, Yash D.; Carranza, Ivonne Escorcia; Cumming, David R. S.Optics Express (2018), 26 (8), 10408-10420CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)We exptl. demonstrate a CMOS compatible medium wave IR metal-insulator-metal (MIM) metamaterial absorber structure where for a single dielec. spacer thickness at least 93% absorption is attained for 10 sep. bands centered at 3.08, 3.30, 3.53, 3.78, 4.14, 4.40, 4.72, 4.94, 5.33, 5.60 μm. Previous hyperspectral MIM metamaterial absorber designs required that the thickness of the dielec. spacer layer be adjusted in order to attain selective unity absorption across the band of interest thereby increasing complexity and cost. We show that the absorption characteristics of the hyperspectral metamaterial structures are polarization insensitive and invariant for oblique incident angles up to 25°making them suitable for practical implementation in an imaging system. Finally, we also reveal that under TM illumination and at certain oblique incident angles there is an extremely narrowband Fano resonance (Q > 50) between the MIM absorber mode and the surface plasmon polariton mode that could have applications in hazardous/toxic gas identification and biosensing.
- 31Frey, L.; Parrein, P.; Raby, J.; Pellé, C.; Hérault, D.; Marty, M.; Michailos, J. Color Filters Including Infrared Cut-off Integrated on CMOS Image Sensor. Opt. Express 2011, 19 (14), 13073, DOI: 10.1364/OE.19.013073[Crossref], [PubMed], [CAS], Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXptFakurk%253D&md5=7fd819838c1a680c42f4c68556166210Color filters including infrared cut-off integrated on CMOS image sensorFrey, Laurent; Parrein, Pascale; Raby, Jacques; Pelle, Catherine; Herault, Didier; Marty, Michel; Michailos, JeanOptics Express (2011), 19 (14), 13073-13080CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)A color image was taken with a CMOS image sensor without any IR cut-off filter, using red, green and blue metal/dielec. filters arranged in Bayer pattern with 1.75μm pixel pitch. The three colors were obtained by a thickness variation of only two layers in the 7-layer stack, with a technol. process including four photolithog. levels. The thickness of the filter stack was only half of the traditional color resists, potentially enabling a redn. of optical crosstalk for smaller pixels. Both color errors and signal to noise ratio derived from optimized spectral responses are expected to be similar to color resists assocd. with IR filter.
- 32Yoon, Y.-T.; Lee, S.-S. Transmission Type Color Filter Incorporating a Silver Film Based Etalon. Opt. Express 2010, 18 (5), 5344, DOI: 10.1364/OE.18.005344[Crossref], [PubMed], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivFOgsLY%253D&md5=d17e12c02dda8cbbc34caa441919881bTransmission type color filter incorporating a silver film based etalonYoon, Yeo-Taek; Lee, Sang-ShinOptics Express (2010), 18 (5), 5344-5349CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)Transmission type color filters based on a thin film Ag-SiO2-Ag etalon were built on a quartz substrate, enabling the IR suppressed transmission and large effective area. They were designed by taking into account the influence of the dispersion characteristics and the thickness of the silver metal. Three different color filters were devised: The cavity length for the red, green and blue filter was 160 nm, 130 nm, and 100 nm resp., while the metal layer was fixed at 25 nm. The obsd. spectral pass band was centered at 650 nm, 555 nm, and 480 nm for the red, green, and blue device; the corresponding bandwidth was about 120 nm, 100 nm, and 120 nm; and the peak transmission was all ∼60%. For the oblique light incidence the angular dependence of the peak relative transmission was measured to be ∼1%/degree. The spectral response of the device was also analyzed for two different polarizations as the tilt angle varied up to 12o, and it was found to be hardly polarization dependent. Finally, as for the positional dependence the relative transmission and the center wavelength were found to vary within 10% and 5 nm resp. over an effective area of 4 × 4 cm2.
- 33Noh, T. H.; Yoon, Y. T.; Lee, S. S.; Choi, D. Y.; Lim, S. C. Highly Angle-Tolerant Spectral Filter Based on an Etalon Resonator Incorporating a High Index Cavity. J. Opt. Soc. Korea 2012, 16 (3), 299– 304, DOI: 10.3807/JOSK.2012.16.3.299[Crossref], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs12jtrjK&md5=69be8cbcadebe3cb8169dfefaf2e468dHighly angle-tolerant spectral filter based on an etalon resonator incorporating a high index cavityNoh, Tae-Hui; Yoon, Yeo-Taek; Lee, Sang-Shin; Choi, Duk-Yong; Lim, Seung-ChanJournal of the Optical Society of Korea (2012), 16 (3), 299-304CODEN: JOSKFI; ISSN:1226-4776. (Optical Society of Korea)A high angular tolerance spectral filter was realized incorporating an etalon, which consists of a TiO2 cavity sandwiched between a pair of Ag/Ge mirrors. The effective angle was substantially extended thanks to the cavity's high refractive index. The device was created by embedding a 313-nm thick TiO2 film in 16-nm thick Ag/Ge films through sputtering, with the Ge layer alleviating the roughness and adhesion of the Ag layer. For normal incidence, the obsd. center wavelength and transmission were ∼900 nm and ∼60%, resp.; throughout the range of 50°, the relative wavelength shift and transmission variation amounted to only ∼0.06 and ∼4%, resp.
- 34Frey, L.; Masarotto, L.; Melhaoui, L. E.; Verrun, S.; Minoret, S.; Rodriguez, G.; André, A.; Ritton, F.; Parrein, P. High-Performance Silver-Dielectric Interference Filters for RGBIR Imaging. Opt. Lett. 2018, 43 (6), 1355– 1358, DOI: 10.1364/OL.43.001355[Crossref], [PubMed], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlOqu7fK&md5=a58b1cc20aa981a509701170846c95e4High-performance silver-dielectric interference filters for RGBIR imagingFrey, Laurent; Masarotto, Lilian; El Melhaoui, Loubna; Verrun, Sophie; Minoret, Stephane; Rodriguez, Guillaume; Andre, Agathe; Ritton, Frederic; Parrein, PascaleOptics Letters (2018), 43 (6), 1355-1358CODEN: OPLEDP; ISSN:1539-4794. (Optical Society of America)New architectures of interference silver-dielec. multilayer filters inspired from induced transmission designs are investigated with the prospect of high-performance red-green-blue (RGB) complementary metal oxide semiconductor imaging. The optimized designs provide combined colorimetric, signal-to-noise ratio and sensitivity performances similar to the traditional org. color filters, but without the equirement of an external IR (IR)-cut filter, which enables the integration of addnl. channels such as white or IR, in addn. to RGB. Due to the sub-micrometer thickness of the stacks, this is a unique soln. for fully integrated, high-performance multispectral filters patterned in very small pixels. The concept is demonstrated by a wafer-scale prototype with RGBIR filters patterned down to 1.4 μm adjacent pixels with up to 80% transmission.
- 35Yang, Z.; Chen, Y.; Zhou, Y.; Wang, Y.; Dai, P.; Zhu, X.; Duan, H. Microscopic Interference Full-Color Printing Using Grayscale-Patterned Fabry–Perot Resonance Cavities. Adv. Opt. Mater. 2017, 5 (10), 1700029 DOI: 10.1002/adom.201700029 .
- 36Chen, Y.; Duan, X.; Matuschek, M.; Zhou, Y.; Neubrech, F.; Duan, H.; Liu, N. Dynamic Color Displays Using Stepwise Cavity Resonators. Nano Lett. 2017, 17 (9), 5555– 5560, DOI: 10.1021/acs.nanolett.7b02336[ACS Full Text
], [CAS], Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFyqs7nK&md5=a589bcc629fd1ffb84e6cdbcfaad01d0Dynamic Color Displays Using Stepwise Cavity ResonatorsChen, Yiqin; Duan, Xiaoyang; Matuschek, Marcus; Zhou, Yanming; Neubrech, Frank; Duan, Huigao; Liu, NaNano Letters (2017), 17 (9), 5555-5560CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)High-resoln. multicolor printing based on pixelated optical nanostructures is of great importance for promoting advances in color display science. So far, most of the work in this field has been focused on achieving static colors, limiting many potential applications. This inevitably calls for the development of dynamic color displays with advanced and innovative functionalities. In this Letter, we demonstrate a novel dynamic color printing scheme using magnesium-based pixelated Fabry-P´erot cavities by gray scale nanolithog. With controlled hydrogenation and dehydrogenation, magnesium undergoes unique metal and dielec. transitions, enabling distinct blank and color states from the pixelated Fabry-P´erot resonators. Following such a scheme, we first demonstrate dynamic Ishihara plates, in which the encrypted images can only be read out using hydrogen as information decoding key. We also demonstrate a new type of dynamic color generation, which enables fascinating transformations between black/white printing and color printing with fine tonal tuning. Our work will find wide-ranging applications in full-color printing and displays, colorimetric sensing, information encryption and anticounterfeiting. - 37Wang, Y.; Zheng, M.; Ruan, Q.; Zhou, Y.; Chen, Y.; Dai, P.; Yang, Z.; Lin, Z.; Long, Y.; Li, Y. Stepwise-Nanocavity-Assisted Transmissive Color Filter Array Microprints. Research 2018, 2018, 1– 10, DOI: 10.1155/2018/8109054
- 38Lumerical Inc. www.Lumerical.Com/Tcad-Products/Fdtd/.Google ScholarThere is no corresponding record for this reference.
- 39Takigawa, T.; Kawabuchi, K.; Yoshimi, M.; Kato, Y. High Voltage Electron Beam Lithography. Microelectron. Eng. 1983, 1, 121– 142, DOI: 10.1016/0167-9317(83)90025-4
- 40Taguchi, H.; Enokido, M. Technology of Color Filter Materials for Image Sensor. Int. Image Sens. Work. 2011, 34– 37Google ScholarThere is no corresponding record for this reference.
Cited By
Abstract

Figure 1

Figure 1. Multispectral filter arrays (MSFAs) using grayscale lithography with metal–insulator–metal (MIM) geometry. (a) Schematic: (i) using a customized MSFA atop a monochrome image sensor for multispectral imaging. (ii) 3D MIM structure of MSFA with inset detailing layers. The wavelength transmitted to each pixel below the MIM structures is controlled with the single-step lithographic fabrication process. (b) MSFA fabrication process: (i) a spatially varying grayscale exposure dose results in a spatially varying wavelength transmission profile. (ii) Calculated grayscale exposure dose profile corresponding to remaining resist thickness profiles (“resist sensitivity” curve). An ultrathin noble metal (Ag) layer on glass (SiO2) acts both to dissipate accumulated charge and as the bottom mirror of the filter. (iii) A spatially variant dose modulated exposure leaves a 3D resist profile postdevelopment. (iv) Post-metal-deposition: with a top metal (mirror) layer, the spatially varying 3D resist profile acts to filter the light according to the eigenmode solution of the stack. (v) Final spectral transmittance profiles of MIM structures.
Figure 2

Figure 2. Grayscale exposure dose to color: experimental verification. (a) Finite-difference time-domain (FDTD) simulations of the optical transmission from a continuous Ag-based MIM cavity as a function of varying insulator thickness, with geometry: SiO2(bulk)–Ag(26 nm)–resist (n = 1.653)–Ag(26 nm)–MgF2(12 nm). (b) Experimental demonstration of grayscale-to-dose pattern with the same layers as in (a): (i) Transmission spectra from dose-modulated 5 μm × 5 μm squares (optical micrograph shown in inset), which results in increasing thickness and hence varying peak wavelengths; (ii) measured curve, using an AFM, linking dose and thickness (standard deviation error bars in blue, with overlaid polynomial-fitted red line). Only the first-order resonance is present at low doses, but for higher doses (>50 μC cm–2), the second-order mode is also excited. (c) Dose-modulated 5 μm × 5 μm pixel array with 10 μm spacing: (i) dose-modulated pattern, (ii) optical micrograph, and (iii) corresponding AFM data. (d) Same as (c) but with zero dead space.
Figure 3

Figure 3. Demonstration of the versatility of grayscale MSFAs through patterned design variety. (a) Optical micrograph (with magnified inset) of the University of Cambridge logo text composed of 10 μm pixels with a randomized exposure dose profile, hence random colors in transmission. (b) RGB+NIR MSFA (bands labeled in inset) with (i) optical micrograph in transmission and (ii) respective transmission spectra of the wavelength bands. (c) Photograph of three identically processed chips with a range of patterned designs on each chip with varying complexity. Each chip is processed in a single lithographic step in G-EBL. (d) Spectrally “ordered” 4 × 3 mosaic: (i) optical micrograph; (ii) transmission spectra. (e) 25 μm linearly variable filter pixel design: (i) optical micrograph; (ii) AFM micrograph of the unit cell showing the in-plane height variation. (f) Optical micrograph (with magnified inset) of an array of RGB pixels with exponentially (2–n) decreasing pixel width, starting from 10 μm. (g) 25 μm discrete spiral phase pixel design: (i) optical micrograph; (ii) AFM micrograph. Transmission spectra represent averages of five different acquisitions, taken at random positions across the array.
Figure 4

Figure 4. Multispectral imaging through a Bayer filter design and 9-band (3 × 3) MSFA. Bayer filter: (a) Optical micrograph of the mosaic with respective transmission spectra (b) of the 3 bands (RGB). (c) Imaging: Physical representation of the MSFA in front of the image sensor: experimental AFM micrograph, optical micrograph, and image sensor schematic, where d is the distance of the MSFA from the sensor plane (∼1 mm). The experimental imaging setup is shown in SI Figure S16. (d) A snapshot of the imaging test scene, including Macbeth ColorChecker chart and Rubik’s cube, captured with a monochrome image sensor through our mosaic (top) and using a conventional smartphone (bottom), for reference. Aside from demosaicing, there is no postprocessing (enhancement) of the color in the image acquired through our mosaic. 3 × 3 MSFA: (e) Optical micrograph of the 3 × 3 mosaic with respective transmission spectra (f) of the 9 bands (labeled) in the MSFA. (g) Multispectral imaging: Schematic representation of the MSFA in front of the image sensor: experimental AFM micrograph, optical micrograph, and image sensor schematic, where d is the distance of the MSFA from the sensor plane (∼1 mm). 2D intensity matrices from the monochrome image sensor (captured through the MSFA) with illumination from a supercontinuum source are shown in SI Section S 3.3 and SI Video S1 at four different center wavelengths: 500, 550, 600, 650 nm; fwhm 10 ± 2 nm. (h) Multispectral test scene comprising a rear-illuminated filter wheel with four different bandpass filters. (Top) “Raw” color image captured using the monochrome image sensor through our MSFA with individual MSFA pixels visible. (Bottom) Reference image of test scene (comprising 4 bandpass filters across the visible spectrum) taken using a conventional smartphone image sensor. (i) Demosaiced color-coded images for four different wavelength bands obtained from the “raw” image in (h) (top), with labels denoting band.
Figure 5

Figure 5. Wafer-scale grayscale-to-color MSFA fabrication. Photolithography-based MSFA fabrication process flow schematic comparing two proposed approaches: a grayscale photomask (a) or binary photomask (b); both result in equivalent MSFAs. (a) (i) 3 × 3 grayscale photomask: 9 levels of optical transmission, one per spectral band. A single flood exposure can be performed imparting a spatially varying dose profile into the photoresist (ii). (b) (i) 3 × 3 binary photomask: A single transparent pixel is repeated in a 3 × 3 array (MSFA unit cell). The mask is translated in-plane for each spectral pixel, with varying exposure levels (ii–iv). Once processed, the spectral response of the final MSFA (v) is identical to that from (a). (c) Photograph of a 3 in. wafer with ∼32 9-band MSFAs (utilizing second-order resonances), with a zoomed-in region captured with a macro lens (d) and tiled SEM micrograph (e) of the same region. (f) Optical micrograph (transmission) of a different region of the wafer, with labeled equivalent exposure pattern (inset) and corresponding transmission spectra (g) for each spectral band. (h) Photograph of two 3 in. MSFA wafers (utilizing first- and second-order resonances), with optical micrograph of one MSFA (i) and its corresponding transmission spectra for each band (j).
References
ARTICLE SECTIONSThis article references 40 other publications.
- 1Kuroda, T. Essential Principles of Image Sensors; CRC Press, 2017.
- 2Lu, G.; Fei, B. Medical Hyperspectral Imaging: A Review. J. Biomed. Opt. 2014, 19 (1), 010901 DOI: 10.1117/1.JBO.19.1.010901[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVKms7rF&md5=00c5cb61bbe4e24944cc5e199e94ef0bMedical hyperspectral imaging: a reviewLu, Guolan; Fei, BaoweiJournal of Biomedical Optics (2014), 19 (1), 010901/1-010901/23CODEN: JBOPFO; ISSN:1083-3668. (Society of Photo-Optical Instrumentation Engineers)A review. Hyperspectral imaging (HSI) is an emerging imaging modality for medical applications, esp. in disease diagnosis and image-guided surgery. HSI acquires a three-dimensional dataset called hypercube, with two spatial dimensions and one spectral dimension. Spatially resolved spectral imaging obtained by HSI provides diagnostic information about the tissue physiol., morphol., and compn. This review paper presents an overview of the literature on medical hyperspectral imaging technol. and its applications. The aim of the survey is threefold: an introduction for those new to the field, an overview for those working in the field, and a ref. for those searching for literature on a specific application.
- 3Lapray, P. J.; Wang, X.; Thomas, J. B.; Gouton, P. Multispectral Filter Arrays: Recent Advances and Practical Implementation. Sensors 2014, 14 (11), 21626– 21659, DOI: 10.3390/s141121626[Crossref], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2M3psFynsQ%253D%253D&md5=ba13ebbb41eab04bae2d9acf695fe2d5Multispectral filter arrays: recent advances and practical implementationLapray Pierre-Jean; Wang Xingbo; Thomas Jean-Baptiste; Gouton PierreSensors (Basel, Switzerland) (2014), 14 (11), 21626-59 ISSN:.Thanks to some technical progress in interferencefilter design based on different technologies, we can finally successfully implement the concept of multispectral filter array-based sensors. This article provides the relevant state-of-the-art for multispectral imaging systems and presents the characteristics of the elements of our multispectral sensor as a case study. The spectral characteristics are based on two different spatial arrangements that distribute eight different bandpass filters in the visible and near-infrared area of the spectrum. We demonstrate that the system is viable and evaluate its performance through sensor spectral simulation.
- 4Bayer, B. E. Color Imaging Array. US3971065A, 1975.Google ScholarThere is no corresponding record for this reference.
- 5Geelen, B.; Tack, N.; Lambrechts, A. A Compact Snapshot Multispectral Imager with a Monolithically Integrated Per-Pixel Filter Mosaic. Proc. SPIE 2014, 8974, 89740L DOI: 10.1117/12.2037607 .
- 6Hagen, N.; Kudenov, M. W. Review of Snapshot Spectral Imaging Technologies. Opt. Eng. 2013, 52 (9), 090901 DOI: 10.1117/1.OE.52.9.090901 .
- 7Coffey, V. C. Multispectral Imaging Moves into the Mainstream. Opt. Photonics News 2012, 23 (4), 18– 24, DOI: 10.1364/OPN.23.4.000018
- 8Carmo, J. P.; Rocha, R. P.; Bartek, M.; De Graaf, G.; Wolffenbuttel, R. F.; Correia, J. H. A Review of Visible-Range Fabry-Perot Microspectrometers in Silicon for the Industry. Opt. Laser Technol. 2012, 44 (7), 2312– 2320, DOI: 10.1016/j.optlastec.2012.03.036[Crossref], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xnsl2lsb0%253D&md5=f598de404f8d3fbad966fbc8e3be23f5A review of visible-range Fabry-Perot microspectrometers in silicon for the industryCarmo, Joao Paulo; Rocha, Rui Pedro; Bartek, Marian; de Graaf, Ger; Wolffenbuttel, Reinoud F.; Correia, Jose HiginoOptics & Laser Technology (2012), 44 (7), 2312-2320CODEN: OLTCAS; ISSN:0030-3992. (Elsevier Ltd.)This review presents microspectrometers in silicon for the industry for measuring light in the visible range, using the Fabry-Perot interferometric technique. The microspectrometers are devices able to do the anal. of the individual spectral components in a given signal and are extensively used on spectroscopy. The anal. of the interaction between the matter and the radiated energy can found huge applications in the industrial sector. The microspectrometers can be divided on three types, detd. by the dispersion element or the used approach and can be found microspectrometers based on prisms, gratings interferometers. Both types of microspectrometers can be used to analyze the spectral content ranging from the UV (<390 nm), passing into the visible region of the electromagnetic spectrum (VIS, 390-760 nm) up to the IR (>760 nm). The microspectrometers in silicon are versatile microinstruments because silicon-compatible techniques can be used to assembly both the optical components with the readout and control electronics, thus resulting high-vol. with high-reproducibility and low-cost batch fabrications. A compensation technique for minimizing the scattered light effects on interferometers was implemented and is also a contribution of this paper. Fabry-Perot microspectrometers for the visible range are discussed in depth for use in industrial applications.
- 9Dillon, P. L. P.; Brault, A. T.; Horak, J. R.; Garcia, E.; Martin, T. W.; Light, W. A. Fabrication and Performance of Color Filter Arrays for Solid- State Imagers. IEEE Trans. Electron Devices 1978, 25, 97 DOI: 10.1109/T-ED.1978.19045 .
- 10Chen, Q.; Hu, X.; Wen, L.; Yu, Y.; Cumming, D. R. S. Nanophotonic Image Sensors. Small 2016, 12 (36), 4922– 4935, DOI: 10.1002/smll.201600528[Crossref], [PubMed], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XovVamt7o%253D&md5=53ac33f2a0c097f1cea9864e0cb708feNanophotonic Image SensorsChen, Qin; Hu, Xin; Wen, Long; Yu, Yan; Cumming, David R. S.Small (2016), 12 (36), 4922-4935CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)The increasing miniaturization and resoln. of image sensors bring challenges to conventional optical elements such as spectral filters and polarizers, the properties of which are detd. mainly by the materials used, including dye polymers. Recent developments in spectral filtering and optical manipulating techniques based on nanophotonics have opened up the possibility of an alternative method to control light spectrally and spatially. By integrating these technologies into image sensors, it will become possible to achieve high compactness, improved process compatibility, robust stability and tunable functionality. In this Review, recent representative achievements on nanophotonic image sensors are presented and analyzed including image sensors with nanophotonic color filters and polarizers, metamaterial-based THz image sensors, filter-free nanowire image sensors and nanostructured-based multispectral image sensors. This novel combination of cutting edge photonics research and well-developed com. products may not only lead to an important application of nanophotonics but also offer great potential for next generation image sensors beyond Moore's Law expectations.
- 11Macleod, H. Thin-Film Optical Filters, third ed.; Institute of Physics Publishing, 1986.
- 12Kristensen, A.; Yang, J. K. W.; Bozhevolnyi, S. I.; Link, S.; Nordlander, P.; Halas, N. J.; Mortensen, N. A. Plasmonic Colour Generation. Nat. Rev. Mater. 2017, 2 (1), 1– 15, DOI: 10.1038/natrevmats.2016.88
- 13Shah, Y. D.; Grant, J.; Hao, D.; Kenney, M.; Pusino, V.; Cumming, D. R. S. Ultra-Narrow Line Width Polarization-Insensitive Filter Using a Symmetry-Breaking Selective Plasmonic Metasurface. ACS Photonics 2018, 5 (2), 663– 669, DOI: 10.1021/acsphotonics.7b01011[ACS Full Text
], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGgurrK&md5=9ad2b9f20923e9f4b907ba3aa5eab991Ultra-narrow Line Width Polarization-Insensitive Filter Using a Symmetry-Breaking Selective Plasmonic MetasurfaceShah, Yash D.; Grant, James; Hao, Danni; Kenney, Mitchell; Pusino, Vincenzo; Cumming, David R. S.ACS Photonics (2018), 5 (2), 663-669CODEN: APCHD5; ISSN:2330-4022. (American Chemical Society)Plasmonic metasurfaces provide unprecedented control of the properties of light. By designing symmetry-breaking nanoholes in a metal sheet and engineering the optical properties of the metal using geometry, highly selective transmission and polarization control of light is obtained. To date such plasmonic filters have exhibited broad (>200 nm) transmission line widths in the NIR and as such are unsuitable for applications requiring narrow passbands, e.g., multispectral imaging. A novel subwavelength elliptical and circular nanohole array in a metallic film that simultaneously exhibits high transmission efficiency, polarization insensitivity, and narrow line width is presented. The exptl. obtained line width is 79 nm with a transmission efficiency of 44%. By examg. the elec. and magnetic field distributions for various incident polarizations at the transmission peak the narrowband characteristics are due to a Fano resonance. Agreement is obtained between the exptl. data, simulations, and anal. calcns. The design can be modified to operate in other regions of the electromagnetic spectrum, and these filters may be integrated with suitable detectors such as photodiodes and single-photon avalanche diode arrays. - 14Williams, C.; Rughoobur, G.; Flewitt, A. J.; Wilkinson, T. D. Nanostructured Plasmonic Metapixels. Sci. Rep. 2017, 7 (1), 7745, DOI: 10.1038/s41598-017-08145-0[Crossref], [PubMed], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC1cfms1SnsQ%253D%253D&md5=2f7acb33e3907077a48bc34c3a26dec2Nanostructured plasmonic metapixelsWilliams Calum; Wilkinson Timothy D; Rughoobur Girish; Flewitt Andrew JScientific reports (2017), 7 (1), 7745 ISSN:.State-of-the-art pixels for high-resolution microdisplays utilize reflective surfaces on top of electrical backplanes. Each pixel is a single fixed color and will usually only modulate the amplitude of light. With the rise of nanophotonics, a pixel's relatively large surface area (~10 μm(2)), is in effect underutilized. Considering the unique optical phenomena associated with plasmonic nanostructures, the scope for use in reflective pixel technology for increased functionality is vast. Yet in general, low reflectance due to plasmonic losses, and sub-optimal design schemes, have limited the real-world application. Here we demonstrate the plasmonic metapixel; which permits high reflection capability whilst providing vivid, polarization switchable, wide color gamut filtering. Ultra-thin nanostructured metal-insulator-metal geometries result in the excitation of hybridized absorption modes across the visible spectrum. These modes include surface plasmons and quasi-guided modes, and by tailoring the absorption modes to exist either side of target wavelengths, we achieve pixels with polarization dependent multicolor reflection on mirror-like surfaces. Because the target wavelength is not part of a plasmonic process, subtractive color filtering and mirror-like reflection occurs. We demonstrate wide color-range pixels, RGB pixel designs, and in-plane Gaussian profile pixels that have the potential to enable new functionality beyond that of a conventional 'square' pixel.
- 15Kumar, K.; Duan, H.; Hegde, R. S.; Koh, S. C. W.; Wei, J. N.; Yang, J. K. W. Printing Colour at the Optical Diffraction Limit. Nat. Nanotechnol. 2012, 7 (9), 557– 561, DOI: 10.1038/nnano.2012.128[Crossref], [PubMed], [CAS], Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFOgsbzL&md5=f52d4449163bb4ba854d0cf90ea2acfbPrinting color at the optical diffraction limitKumar, Karthik; Duan, Huigao; Hegde, Ravi S.; Koh, Samuel C. W.; Wei, Jennifer N.; Yang, Joel K. W.Nature Nanotechnology (2012), 7 (9), 557-561CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)The highest possible resoln. for printed color images is detd. by the diffraction limit of visible light. To achieve this limit, individual color elements (or pixels) with a pitch of 250 nm are required, translating into printed images at a resoln. of ∼100,000 dots per in. (d.p.i.). However, methods for dispensing multiple colorants or fabricating structural color through plasmonic structures have insufficient resoln. and limited scalability. Here, we present a non-colorant method that achieves bright-field color prints with resoln. up to the optical diffraction limit. Color information is encoded in the dimensional parameters of metal nanostructures, so that tuning their plasmon resonance dets. the colors of the individual pixels. Our color-mapping strategy produces images with both sharp color changes and fine tonal variations, is amenable to large-vol. color printing via nanoimprint lithog., and could be useful in making micro-images for security, steganog., nanoscale optical filters and high-d. spectrally encoded optical data storage.
- 16Burgos, S. P.; Yokogawa, S.; Atwater, H. A. Color Imaging via Nearest Neighbor Hole Coupling in Plasmonic Color Filters Integrated onto a Complementary Metal-Oxide Semiconductor Image Sensor. ACS Nano 2013, 7 (11), 10038– 10047, DOI: 10.1021/nn403991d[ACS Full Text
], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs1Oku77I&md5=a8fb50006f555fe474696093dcaeaff1Color imaging via nearest neighbor hole coupling in plasmonic color filters integrated onto a complementary metal-oxide semiconductor image sensorBurgos, Stanley P.; Yokogawa, Sozo; Atwater, Harry A.ACS Nano (2013), 7 (11), 10038-10047CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)State-of-the-art CMOS imagers are composed of very small pixels, so it is crit. for plasmonic imaging to understand the optical response of finite-size hole arrays and their coupling efficiency to CMOS image sensor pixels. Here, the authors demonstrate that the transmission spectra of finite-size hole arrays can be accurately described by only accounting for up to the second nearest-neighbor scattering-absorption interactions of hole pairs, thus making hole arrays appealing for close-packed color filters for imaging applications. Using this model, they find that the peak transmission efficiency of a square-shaped hole array with a triangular lattice reaches ∼90% that of an infinite array at an extent of ∼6 × 6 μm2, the smallest size array showing near-infinite array transmission properties. Finally, they exptl. validate their findings by investigating the transmission and imaging characteristics of a 360 × 320 pixel plasmonic color filter array composed of 5.6 × 5.6 μm2 RGB color filters integrated onto a com. black and white 1/2.8 in. CMOS image sensor, demonstrating full-color high resoln. plasmonic imaging. Their results show good color fidelity with a 6-color-averaged color difference metric (ΔE) in the range of 16.6-19.3, after white balancing and color-matrix correcting raw images taken with f-nos. ranging from 1.8 to 16. The integrated peak filter transmission efficiencies are measured to be in the 50% range, with a FWHM of 200 nm for all three RGB filters, in good agreement with the spectral response of isolated unmounted color filters. - 17Shaltout, A. M.; Kim, J.; Boltasseva, A.; Shalaev, V. M.; Kildishev, A. V. Ultrathin and Multicolour Optical Cavities with Embedded Metasurfaces. Nat. Commun. 2018, 9 (1), 1– 7, DOI: 10.1038/s41467-018-05034-6[Crossref], [PubMed], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtlSlurnL&md5=089b9cd25476f353e67a0ec22bc17e81Ultrathin and multicolour optical cavities with embedded metasurfacesShaltout, Amr M.; Kim, Jongbum; Boltasseva, Alexandra; Shalaev, Vladimir M.; Kildishev, Alexander V.Nature Communications (2018), 9 (1), 1-7CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)Over the past years, photonic metasurfaces have demonstrated their remarkable and diverse capabilities in advanced control over light propagation. Here, we demonstrate that these artificial films of deeply subwavelength thickness also offer new unparalleled capabilities in decreasing the overall dimensions of integrated optical systems. We propose an original approach of embedding a metasurface inside an optical cavity-one of the most fundamental optical elements-to drastically scale-down its thickness. By modifying the Fabry-Pe´rot interferometric principle, this methodol. is shown to reduce the metasurface-based nanocavity thickness below the conventional λ/(2n) min. In addn., the nanocavities with embedded metasurfaces can support independently tunable resonances at multiple bands. As a proof-of-concept, using nanostructured metasurfaces within 100-nm nanocavities, we exptl. demonstrate high spatial resoln. color filtering and spectral imaging. The proposed approach can be extrapolated to compact integrated optical systems on-a-chip such as VCSEL's, high-resoln. spatial light modulators, imaging spectroscopy systems, and bio-sensors.
- 18Davis, M. S.; Zhu, W.; Xu, T.; Lee, J. K.; Lezec, H. J.; Agrawal, A. Aperiodic Nanoplasmonic Devices for Directional Colour Filtering and Sensing. Nat. Commun. 2017, 8 (1), DOI: 10.1038/s41467-017-01268-y .
- 19Yokogawa, S.; Burgos, S. P.; Atwater, H. A. Plasmonic Color Filters for CMOS Image Sensor Applications. Nano Lett. 2012, 12 (8), 4349– 4354, DOI: 10.1021/nl302110z[ACS Full Text
], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVejtbjJ&md5=0cb1613783d0b1dc386168673aa5a552Plasmonic Color Filters for CMOS Image Sensor ApplicationsYokogawa, Sozo; Burgos, Stanley P.; Atwater, Harry A.Nano Letters (2012), 12 (8), 4349-4354CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)We report on the optical properties of plasmonic hole arrays as they apply to requirements for plasmonic color filters designed for state-of-the-art Si CMOS image sensors. The hole arrays are composed of hexagonally packed subwavelength sized holes on a 150 nm Al film designed to operate at the primary colors of red, green, and blue. Hole array plasmonic filters show peak transmission in the 40-50% range for large (>5 × 5 μm2) size filters and maintain their filtering function for pixel sizes as small as ∼1 × 1 μm2, albeit at a cost in transmission efficiency. Hole array filters are found to robust with respect to spatial crosstalk between pixel within our detection limit and preserve their filtering function in arrays contg. random defects. Anal. of hole array filter transmittance and crosstalk suggests that nearest neighbor hole-hole interactions rather than long-range interactions play the dominant role in the transmission properties of plasmonic hole array filters. We verify this via a simple nearest neighbor model that correctly predicts the hole array transmission efficiency as a function of the no. of holes. - 20Franklin, D.; Chen, Y.; Vazquez-Guardado, A.; Modak, S.; Boroumand, J.; Xu, D.; Wu, S. T.; Chanda, D. Polarization-Independent Actively Tunable Colour Generation on Imprinted Plasmonic Surfaces. Nat. Commun. 2015, 6, 1– 8, DOI: 10.1038/ncomms8337
- 21James, T. D.; Mulvaney, P.; Roberts, A. The Plasmonic Pixel: Large Area, Wide Gamut Color Reproduction Using Aluminum Nanostructures. Nano Lett. 2016, 16 (6), 3817– 3823, DOI: 10.1021/acs.nanolett.6b01250[ACS Full Text
], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XnslCktr4%253D&md5=75abe542d001fd89de1c0e290a2c2afdThe Plasmonic Pixel: Large Area, Wide Gamut Color Reproduction Using Aluminum NanostructuresJames, Timothy D.; Mulvaney, Paul; Roberts, AnnNano Letters (2016), 16 (6), 3817-3823CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)We demonstrate a new plasmonic pixel (PP) design that produces a full-color optical response over macroscopic dimensions. The pixel design employs arrays of aluminum nanorods "floating" above their Babinet complementary screen, Concepts from conventional cyan magenta yellow key (CMYK) printing techniques and red green blue (RGB) digital displays are integrated with nanophotonic design principles and adapted to the prodn. of PP elements. The fundamental PP color blocks of CMYK are implemented via a composite plasmonic nanoantenna/slot design and then mixed in a digital display analog 3 × 3 array to produce a broad-gamut PP. The PP goes beyond current investigations into plasmonic color prodn. by enabling a broad color gamut and phys. large plasmonic color features/devices/images. The use of nanorods also leads to a color response that is polarization tunable. Furthermore, devices are fabricated using aluminum and the fabrication strategy is compatible with inexpensive, rapid-throughput, nanoimprint approaches. Here we quantify, both computationally and exptl., the performance of the PP. Spectral data from a test palette is obtained and a large area (>1.5 cm lateral dimensions) reprodn. of a photograph is generated exemplifying the technique. - 22Jahani, S.; Jacob, Z. All-Dielectric Metamaterials. Nat. Nanotechnol. 2016, 11 (1), 23– 36, DOI: 10.1038/nnano.2015.304[Crossref], [PubMed], [CAS], Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XjslGqtQ%253D%253D&md5=31e733bf7637c01b93600c57f2476e4aAll-dielectric metamaterialsJahani, Saman; Jacob, ZubinNature Nanotechnology (2016), 11 (1), 23-36CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)A review. The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the elec. and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielec. nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), resp., but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there was a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all 4 quadrants of possible permittivities and permeabilities were achieved using completely transparent and high-refractive-index dielec. building blocks. An emerging class of all-dielec. metamaterials consisting of anisotropic crystals was shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. A broad outline is presented of the whole range of electromagnetic effects obsd. using all-dielec. metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Current challenges and future goals for the field at the intersection with quantum, thermal and Si photonics, as well as biomimetic metasurfaces are discussed.
- 23Genevet, P.; Capasso, F.; Aieta, F.; Khorasaninejad, M.; Devlin, R. Recent Advances in Planar Optics: From Plasmonic to Dielectric Metasurfaces. Optica 2017, 4 (1), 139, DOI: 10.1364/OPTICA.4.000139[Crossref], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXjsFGisLw%253D&md5=c20386207d233de3861bbb9eb4fb9c44Recent advances in planar optics: from plasmonic to dielectric metasurfacesGenevet, Patrice; Capasso, Federico; Aieta, Francesco; Khorasaninejad, Mohammadreza; Devlin, RobertOptica (2017), 4 (1), 139-152CODEN: OPTIC8; ISSN:2334-2536. (Optical Society of America)This article reviews recent progress leading to the realization of planar optical components made of a single layer of phase shifting nanostructures. After introducing the principles of planar optics and discussing earlier works on subwavelength diffractive optics, we introduce a classification of metasurfaces based on their different phase mechanisms and profiles and a comparison between plasmonic and dielec. metasurfaces. We place particular emphasis on the recent developments on elec. and magnetic field control of light with dielec. nanostructures and highlight the phys. mechanisms and designs required for efficient all-dielec. metasurfaces. Practical devices of general interest such as metalenses, beam deflectors, holograms, and polarizing interfaces are discussed, including high-performance metalenses at visible wavelengths. Successful strategies to achieve achromatic response at selected wavelengths and near unity transmission/reflection efficiency are discussed. Dielec. metasurfaces and dispersion management at interfaces open up technol. opportunities for applications including wavefront control, lightwt. imaging systems, displays, electronic consumer products, and conformable and wearable optics.
- 24Wang, P.; Menon, R. Ultra-High-Sensitivity Color Imaging via a Transparent Diffractive-Filter Array and Computational Optics. Optica 2015, 2 (11), 933, DOI: 10.1364/OPTICA.2.000933
- 25Kats, M. A.; Blanchard, R.; Genevet, P.; Capasso, F. Nanometre Optical Coatings Based on Strong Interference Effects in Highly Absorbing Media. Nat. Mater. 2013, 12 (1), 20– 24, DOI: 10.1038/nmat3443[Crossref], [PubMed], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsV2rsL7F&md5=ee0129e1f718ae1449857ebc355ac65eNanometre optical coatings based on strong interference effects in highly absorbing mediaKats, Mikhail A.; Blanchard, Romain; Genevet, Patrice; Capasso, FedericoNature Materials (2013), 12 (1), 20-24CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Optical coatings, which consist of ≥1 films of dielec. or metallic materials, are widely used in applications ranging from mirrors to eyeglasses and photog. lenses. Many conventional dielec. coatings rely on Fabry-Perot-type interference, involving multiple optical passes through transparent layers with thicknesses of the order of the wavelength to achieve functionalities such as anti-reflection, high-reflection and dichroism. Highly absorbing dielecs. are typically not used because it is generally accepted that light propagation through such media destroys interference effects. Under appropriate conditions interference can instead persist in ultrathin, highly absorbing films of a few to tens of nanometers in thickness, and demonstrate a new type of optical coating comprising such a film on a metallic substrate, which selectively absorbs various frequency ranges of the incident light. These coatings have a low sensitivity to the angle of incidence and require minimal amts. of absorbing material that can be as thin as 5-20 nm for visible light. This technol. has the potential for a variety of applications from ultrathin photodetectors and solar cells to optical filters, to labeling, and even the visual arts and jewellery.
- 26Li, Z.; Butun, S.; Aydin, K. Large-Area, Lithography-Free Super Absorbers and Color Filters at Visible Frequencies Using Ultrathin Metallic Films. ACS Photonics 2015, 2 (2), 183– 188, DOI: 10.1021/ph500410u[ACS Full Text
], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslent7k%253D&md5=525fb0459545ac29f3b9e286cf9c0d9dLarge-Area, Lithography-Free Super Absorbers and Color Filters at Visible Frequencies Using Ultrathin Metallic FilmsLi, Zhongyang; Butun, Serkan; Aydin, KorayACS Photonics (2015), 2 (2), 183-188CODEN: APCHD5; ISSN:2330-4022. (American Chemical Society)Nanostructured photonic materials enable control and manipulation of light at subwavelength scales and exhibit unique optical functionalities. In particular, plasmonic materials and metamaterials have been widely utilized to achieve spectral transmission, reflection, and absorption filters based on localized or delocalized resonances arising from the interaction of photons with nanostructured materials. Realization of visible-frequency, high-performance, large-area, optical filters based on nanoplasmonic materials is rather challenging due to nanofabrication related problems (cost, fabrication imperfection, surface roughness) and optical losses of metals. Here, we propose and demonstrate large-area perfect absorbers and transmission filters that overcome difficulties assocd. with the nanofabrication using a lithog.-free approach. We also utilize and benefit from the optical losses in metals in our optical filter designs. Our resonant optical filter design is based on a modified, asym. metal-insulator-metal (MIM) based Fabry-Perot cavity with plasmonic, lossy ultrathin (∼30 nm) metallic films used as the top metallic layer. We demonstrated a narrow bandwidth (∼17 nm) super absorber with 97% max. absorption with a performance comparable to nanostructure/nanoparticle-based super absorbers. We also investigated transmission (color) filters using ultrathin metallic films, in which different colors can be obtained by controlling the dielec. spacer thickness. With performance parameters of transmittance peak intensity reaching 60% and a narrow-band of ∼40 nm, our color filters exceed the performance of widely studied plasmonic nanohole array based color filters. Proposed asym. Fabry-Perot cavities using ultrathin metallic films could find applications in spectrally selective optical (color and absorber) filters, optoelectronic devices with controlled bandwidth such as narrow-band photodetectors, and light-emitting devices. - 27Kajtár, G.; Kafesaki, M.; Economou, E. N.; Soukoulis, C. M. Theoretical Model of Homogeneous Metal-Insulator-Metal Perfect Multi-Band Absorbers for the Visible Spectrum. J. Phys. D: Appl. Phys. 2016, 49 (5), 55104, DOI: 10.1088/0022-3727/49/5/055104[Crossref], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlyitbjP&md5=958a1061499b620aa05f0afc08dc5edfTheoretical model of homogeneous metal-insulator-metal perfect multi-band absorbers for the visible spectrumKajtar, G.; Kafesaki, M.; Economou, E. N.; Soukoulis, C. M.Journal of Physics D: Applied Physics (2016), 49 (5), 055104/1-055104/6CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)We present a rigorous study of the perfect absorption properties of metal-insulator-metal (MIM) structures in the visible spectrum. We provide a derivation (based on the transfer matrix method) and anal. of the conditions for which the perfect absorption occurs. We show that these conditions are fulfilled when the incident wave excites the eigenmodes of the structure. The quant. anal. allows us to design specific perfect absorbers for our needs. The anal. model is verified by rigorous simulations based on rigorous coupled wave anal., which demonstrate also the angle and polarization insensitivity of the absorption properties of such a structure. Employing the MIM approach and results, we also investigate and demonstrate multiple perfect absorption bands and broad-band absorption in properly designed multilayer metal-insulator systems.
- 28Diest, K.; Dionne, J.; Spain, M. Tunable Color Filters Based on Metal– Insulator– Metal Resonators. Nano Lett. 2009, 9 (7), 2579– 2583, DOI: 10.1021/nl900755b[ACS Full Text
], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXnt1Wrsr8%253D&md5=961e5220803c39daf6a1509a236d09c4Tunable Color Filters Based on Metal-Insulator-Metal ResonatorsDiest, Kenneth; Dionne, Jennifer A.; Spain, Merrielle; Atwater, Harry A.Nano Letters (2009), 9 (7), 2579-2583CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)We report a method for filtering white light into individual colors using metal-insulator-metal resonators. The resonators are designed to support photonic modes at visible frequencies, and dispersion relations are developed for realistic exptl. configurations. Exptl. results indicate that passive Ag/Si3N4/Au resonators exhibit color filtering across the entire visible spectrum. Full field electromagnetic simulations were performed on active resonators for which the resonator length was varied from 1-3 μm and the output slit depth was systematically varied throughout the thickness of the dielec. layer. These resonators are shown to filter colors based on interference between the optical modes within the dielec. layer. By careful design of the output coupling, the resonator can selectively couple to intensity maxima of different photonic modes and, as a result, preferentially select any of the primary colors. We also illustrate how refractive index modulation in metal-insulator-metal resonators can yield actively tunable color filters. Simulations using lithium niobate as the dielec. layer and the top and bottom Ag layers as electrodes, indicate that the output color can be tuned over the visible spectrum with an applied field. - 29Williams, C.; Rughoobur, G.; Flewitt, A. J.; Wilkinson, T. D. Single-Step Fabrication of Thin-Film Linear Variable Bandpass Filters Based on Metal–Insulator–Metal Geometry. Appl. Opt. 2016, 55 (32), 9237, DOI: 10.1364/AO.55.009237[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXkvVSmtro%253D&md5=2dd553cbbddfffbeebafbeb7b1725c35Single-step fabrication of thin-film linear variable bandpass filters based on metal-insulator-metal geometryWilliams, Calum; Rughoobur, Girish; Flewitt, Andrew J.; Wilkinson, Timothy D.Applied Optics (2016), 55 (32), 9237-9241CODEN: APOPAI; ISSN:1559-128X. (Optical Society of America)A single-step fabrication method is presented for ultra-thin, linearly variable optical bandpass filters (LVBFs) based on a metal-insulator-metal arrangement using modified evapn. deposition techniques. This alternate process methodol. offers reduced complexity and cost in comparison to conventional techniques for fabricating LVBFs. We are able to achieve linear variation of insulator thickness across a sample, by adjusting the geometrical parameters of a typical phys. vapor deposition process. We demonstrate LVBFs with spectral selectivity from 400 to 850 nm based on Ag (25 nm) and MgF2 (75-250 nm). Maximum spectral transmittance is measured at ∼70% with a Q-factor of ∼20.
- 30Grant, J.; Kenney, M.; Shah, Y. D.; Escorcia-Carranza, I.; Cumming, D. R. S. CMOS Compatible Metamaterial Absorbers for Hyperspectral Medium Wave Infrared Imaging and Sensing Applications. Opt. Express 2018, 26 (8), 10408, DOI: 10.1364/OE.26.010408[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlKhtbvP&md5=aff14f348ca12713d98b4a7e77beecb6CMOS compatible metamaterial absorbers for hyperspectral medium wave infrared imaging and sensing applicationsGrant, James; Kenney, Mitchell; Shah, Yash D.; Carranza, Ivonne Escorcia; Cumming, David R. S.Optics Express (2018), 26 (8), 10408-10420CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)We exptl. demonstrate a CMOS compatible medium wave IR metal-insulator-metal (MIM) metamaterial absorber structure where for a single dielec. spacer thickness at least 93% absorption is attained for 10 sep. bands centered at 3.08, 3.30, 3.53, 3.78, 4.14, 4.40, 4.72, 4.94, 5.33, 5.60 μm. Previous hyperspectral MIM metamaterial absorber designs required that the thickness of the dielec. spacer layer be adjusted in order to attain selective unity absorption across the band of interest thereby increasing complexity and cost. We show that the absorption characteristics of the hyperspectral metamaterial structures are polarization insensitive and invariant for oblique incident angles up to 25°making them suitable for practical implementation in an imaging system. Finally, we also reveal that under TM illumination and at certain oblique incident angles there is an extremely narrowband Fano resonance (Q > 50) between the MIM absorber mode and the surface plasmon polariton mode that could have applications in hazardous/toxic gas identification and biosensing.
- 31Frey, L.; Parrein, P.; Raby, J.; Pellé, C.; Hérault, D.; Marty, M.; Michailos, J. Color Filters Including Infrared Cut-off Integrated on CMOS Image Sensor. Opt. Express 2011, 19 (14), 13073, DOI: 10.1364/OE.19.013073[Crossref], [PubMed], [CAS], Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXptFakurk%253D&md5=7fd819838c1a680c42f4c68556166210Color filters including infrared cut-off integrated on CMOS image sensorFrey, Laurent; Parrein, Pascale; Raby, Jacques; Pelle, Catherine; Herault, Didier; Marty, Michel; Michailos, JeanOptics Express (2011), 19 (14), 13073-13080CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)A color image was taken with a CMOS image sensor without any IR cut-off filter, using red, green and blue metal/dielec. filters arranged in Bayer pattern with 1.75μm pixel pitch. The three colors were obtained by a thickness variation of only two layers in the 7-layer stack, with a technol. process including four photolithog. levels. The thickness of the filter stack was only half of the traditional color resists, potentially enabling a redn. of optical crosstalk for smaller pixels. Both color errors and signal to noise ratio derived from optimized spectral responses are expected to be similar to color resists assocd. with IR filter.
- 32Yoon, Y.-T.; Lee, S.-S. Transmission Type Color Filter Incorporating a Silver Film Based Etalon. Opt. Express 2010, 18 (5), 5344, DOI: 10.1364/OE.18.005344[Crossref], [PubMed], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivFOgsLY%253D&md5=d17e12c02dda8cbbc34caa441919881bTransmission type color filter incorporating a silver film based etalonYoon, Yeo-Taek; Lee, Sang-ShinOptics Express (2010), 18 (5), 5344-5349CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)Transmission type color filters based on a thin film Ag-SiO2-Ag etalon were built on a quartz substrate, enabling the IR suppressed transmission and large effective area. They were designed by taking into account the influence of the dispersion characteristics and the thickness of the silver metal. Three different color filters were devised: The cavity length for the red, green and blue filter was 160 nm, 130 nm, and 100 nm resp., while the metal layer was fixed at 25 nm. The obsd. spectral pass band was centered at 650 nm, 555 nm, and 480 nm for the red, green, and blue device; the corresponding bandwidth was about 120 nm, 100 nm, and 120 nm; and the peak transmission was all ∼60%. For the oblique light incidence the angular dependence of the peak relative transmission was measured to be ∼1%/degree. The spectral response of the device was also analyzed for two different polarizations as the tilt angle varied up to 12o, and it was found to be hardly polarization dependent. Finally, as for the positional dependence the relative transmission and the center wavelength were found to vary within 10% and 5 nm resp. over an effective area of 4 × 4 cm2.
- 33Noh, T. H.; Yoon, Y. T.; Lee, S. S.; Choi, D. Y.; Lim, S. C. Highly Angle-Tolerant Spectral Filter Based on an Etalon Resonator Incorporating a High Index Cavity. J. Opt. Soc. Korea 2012, 16 (3), 299– 304, DOI: 10.3807/JOSK.2012.16.3.299[Crossref], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs12jtrjK&md5=69be8cbcadebe3cb8169dfefaf2e468dHighly angle-tolerant spectral filter based on an etalon resonator incorporating a high index cavityNoh, Tae-Hui; Yoon, Yeo-Taek; Lee, Sang-Shin; Choi, Duk-Yong; Lim, Seung-ChanJournal of the Optical Society of Korea (2012), 16 (3), 299-304CODEN: JOSKFI; ISSN:1226-4776. (Optical Society of Korea)A high angular tolerance spectral filter was realized incorporating an etalon, which consists of a TiO2 cavity sandwiched between a pair of Ag/Ge mirrors. The effective angle was substantially extended thanks to the cavity's high refractive index. The device was created by embedding a 313-nm thick TiO2 film in 16-nm thick Ag/Ge films through sputtering, with the Ge layer alleviating the roughness and adhesion of the Ag layer. For normal incidence, the obsd. center wavelength and transmission were ∼900 nm and ∼60%, resp.; throughout the range of 50°, the relative wavelength shift and transmission variation amounted to only ∼0.06 and ∼4%, resp.
- 34Frey, L.; Masarotto, L.; Melhaoui, L. E.; Verrun, S.; Minoret, S.; Rodriguez, G.; André, A.; Ritton, F.; Parrein, P. High-Performance Silver-Dielectric Interference Filters for RGBIR Imaging. Opt. Lett. 2018, 43 (6), 1355– 1358, DOI: 10.1364/OL.43.001355[Crossref], [PubMed], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlOqu7fK&md5=a58b1cc20aa981a509701170846c95e4High-performance silver-dielectric interference filters for RGBIR imagingFrey, Laurent; Masarotto, Lilian; El Melhaoui, Loubna; Verrun, Sophie; Minoret, Stephane; Rodriguez, Guillaume; Andre, Agathe; Ritton, Frederic; Parrein, PascaleOptics Letters (2018), 43 (6), 1355-1358CODEN: OPLEDP; ISSN:1539-4794. (Optical Society of America)New architectures of interference silver-dielec. multilayer filters inspired from induced transmission designs are investigated with the prospect of high-performance red-green-blue (RGB) complementary metal oxide semiconductor imaging. The optimized designs provide combined colorimetric, signal-to-noise ratio and sensitivity performances similar to the traditional org. color filters, but without the equirement of an external IR (IR)-cut filter, which enables the integration of addnl. channels such as white or IR, in addn. to RGB. Due to the sub-micrometer thickness of the stacks, this is a unique soln. for fully integrated, high-performance multispectral filters patterned in very small pixels. The concept is demonstrated by a wafer-scale prototype with RGBIR filters patterned down to 1.4 μm adjacent pixels with up to 80% transmission.
- 35Yang, Z.; Chen, Y.; Zhou, Y.; Wang, Y.; Dai, P.; Zhu, X.; Duan, H. Microscopic Interference Full-Color Printing Using Grayscale-Patterned Fabry–Perot Resonance Cavities. Adv. Opt. Mater. 2017, 5 (10), 1700029 DOI: 10.1002/adom.201700029 .
- 36Chen, Y.; Duan, X.; Matuschek, M.; Zhou, Y.; Neubrech, F.; Duan, H.; Liu, N. Dynamic Color Displays Using Stepwise Cavity Resonators. Nano Lett. 2017, 17 (9), 5555– 5560, DOI: 10.1021/acs.nanolett.7b02336[ACS Full Text
], [CAS], Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFyqs7nK&md5=a589bcc629fd1ffb84e6cdbcfaad01d0Dynamic Color Displays Using Stepwise Cavity ResonatorsChen, Yiqin; Duan, Xiaoyang; Matuschek, Marcus; Zhou, Yanming; Neubrech, Frank; Duan, Huigao; Liu, NaNano Letters (2017), 17 (9), 5555-5560CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)High-resoln. multicolor printing based on pixelated optical nanostructures is of great importance for promoting advances in color display science. So far, most of the work in this field has been focused on achieving static colors, limiting many potential applications. This inevitably calls for the development of dynamic color displays with advanced and innovative functionalities. In this Letter, we demonstrate a novel dynamic color printing scheme using magnesium-based pixelated Fabry-P´erot cavities by gray scale nanolithog. With controlled hydrogenation and dehydrogenation, magnesium undergoes unique metal and dielec. transitions, enabling distinct blank and color states from the pixelated Fabry-P´erot resonators. Following such a scheme, we first demonstrate dynamic Ishihara plates, in which the encrypted images can only be read out using hydrogen as information decoding key. We also demonstrate a new type of dynamic color generation, which enables fascinating transformations between black/white printing and color printing with fine tonal tuning. Our work will find wide-ranging applications in full-color printing and displays, colorimetric sensing, information encryption and anticounterfeiting. - 37Wang, Y.; Zheng, M.; Ruan, Q.; Zhou, Y.; Chen, Y.; Dai, P.; Yang, Z.; Lin, Z.; Long, Y.; Li, Y. Stepwise-Nanocavity-Assisted Transmissive Color Filter Array Microprints. Research 2018, 2018, 1– 10, DOI: 10.1155/2018/8109054
- 38Lumerical Inc. www.Lumerical.Com/Tcad-Products/Fdtd/.Google ScholarThere is no corresponding record for this reference.
- 39Takigawa, T.; Kawabuchi, K.; Yoshimi, M.; Kato, Y. High Voltage Electron Beam Lithography. Microelectron. Eng. 1983, 1, 121– 142, DOI: 10.1016/0167-9317(83)90025-4
- 40Taguchi, H.; Enokido, M. Technology of Color Filter Materials for Image Sensor. Int. Image Sens. Work. 2011, 34– 37Google ScholarThere is no corresponding record for this reference.
Supporting Information
ARTICLE SECTIONSThe Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsphotonics.9b01196.
Simulations of transmission and angle dependency; fabrication process optimization and materials considerations (PDF)
Movie illustrating MSFA characterization (AVI)
Terms & Conditions
Electronic Supporting Information files are available without a subscription to ACS Web Editions. The American Chemical Society holds a copyright ownership interest in any copyrightable Supporting Information. Files available from the ACS website may be downloaded for personal use only. Users are not otherwise permitted to reproduce, republish, redistribute, or sell any Supporting Information from the ACS website, either in whole or in part, in either machine-readable form or any other form without permission from the American Chemical Society. For permission to reproduce, republish and redistribute this material, requesters must process their own requests via the RightsLink permission system. Information about how to use the RightsLink permission system can be found at http://pubs.acs.org/page/copyright/permissions.html.





