WO2023166289A1 - Filtre de lumière à métasurface plasmonique et capteur d'imagerie comprenant un filtre de lumière - Google Patents

Filtre de lumière à métasurface plasmonique et capteur d'imagerie comprenant un filtre de lumière Download PDF

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Publication number
WO2023166289A1
WO2023166289A1 PCT/GB2023/050466 GB2023050466W WO2023166289A1 WO 2023166289 A1 WO2023166289 A1 WO 2023166289A1 GB 2023050466 W GB2023050466 W GB 2023050466W WO 2023166289 A1 WO2023166289 A1 WO 2023166289A1
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WIPO (PCT)
Prior art keywords
unit cell
nanoholes
light
metasurface
imaging sensor
Prior art date
Application number
PCT/GB2023/050466
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English (en)
Inventor
Yash Shah
Charles ALTUZARRA
Original Assignee
Metahelios Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB2202821.1A external-priority patent/GB2616271A/en
Application filed by Metahelios Limited filed Critical Metahelios Limited
Publication of WO2023166289A1 publication Critical patent/WO2023166289A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/002—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/008—Surface plasmon devices
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/201—Filters in the form of arrays
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/204—Filters in which spectral selection is performed by means of a conductive grid or array, e.g. frequency selective surfaces
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3058—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state comprising electrically conductive elements, e.g. wire grids, conductive particles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1462—Coatings
    • H01L27/14621—Colour filter arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J4/00—Measuring polarisation of light
    • G01J4/04—Polarimeters using electric detection means

Definitions

  • the present invention relates to a plasmonic metasurface light filter that is particularly suitable for use with imaging sensors
  • Single photon imagers have gained prominence in the field of depth profile or three- dimensional imaging, astrophysics, fluorescence imaging due to their capability of low photon imaging and high acquisition rate imaging.
  • these imaging sensors are only able to detect the intensity of the light. However, this is just a fraction of the information that is in the light field scattered from the object being imaged.
  • Valuable information on an object can be obtained from wavelength, polarization, phase, and temporal characteristics of light. It is standard for achieving color acquisition with cameras to use dichroic films and dye filters in a Bayer pattern.
  • wire grid polarisers have been developed that are sensitive to one polarization of light.
  • Metasurfaces are subwavelength nanostructures. Plasmonic metasurfaces exploit free electron oscillations at the interface between a material of negative permittivity, - s (for example a metal layer) and a material of positive permittivity ,+ s (for example a glass substrate).
  • the metallic layer is deposited and engineered with nanostructures so as to provide a planar mechanism to modulate the incident light.
  • - s for example a metal layer
  • + s for example a glass substrate.
  • the metallic layer is deposited and engineered with nanostructures so as to provide a planar mechanism to modulate the incident light.
  • plasmonic metasurfaces While there are many attractive reasons to try plasmonic metasurfaces, they have a significant disadvantage - efficiency of current plasmonic metasurfaces at visible and near-infrared frequencies can be ⁇ 10%.
  • a plasmonic metasurface light filter comprising planar array of unit cells, each unit cell including a plurality of light- transmissive nanoholes having a substantially elliptical cross-section, each unit cell being individually tunable with respect to frequency and polarization of light to filter by varying geometry of its respective nanoholes.
  • the tuning of the unit cell is optimized with regard to extinction ratio.
  • each nanohole in a unit cell has its elliptical major and minor axes oriented in parallel to the elliptical long axis of the other nanoholes in the unit cell and selected in dependence on the polarization of light to be filtered by the respective unit cell.
  • the size of nanoholes of the unit cells is preferably selected in dependence on the light wavelength to be filtered by the respective unit cell.
  • the array corresponds in size to an imaging sensor, each of the unit cells being positioned to align with a pixel of the imaging sensor when the array is placed over the imaging sensor.
  • the metasurface may comprise an aluminium layer having the nanoholes etched therein.
  • the metasurface may comprise an annealed gold film having the nanoholes etched therein.
  • the metasurface may be capped.
  • Embodiments of the present invention relate to a plasmonic metasurface and in particular to a 2D array of plasmonic metasurface unit cells in which individual unit cells in the array have geometrical properties that are selected in dependence on wavelength and(/or) polarization of light to be filtered by that array element.
  • a single layer of nanostructures etched into a thin metallic film can filter a particular wavelength (color) and polarization simultaneously to form a spectropolarimeter for single photon avalanche diode (SPAD) and CMOS cameras.
  • SBA single photon avalanche diode
  • CMOS complementary metal-oxide-semiconductor
  • embodiments can be used in a pixelated imaging sensor format which can be scaled from blue (450 nm) to SWIR (1-2 pm).
  • per pixel not only can a higher transmission of a designed color be observed but embodiments can incorporate selected polarisation per pixel with an efficient extinction ratio to differentiate from orthogonal polarisations for nanostructure devices.
  • the geometry and arrangement of elliptical nanoholes in a thin metal film provide the simultaneous dual functionality of any color and polarisation selectivity without the use of any bulky optics of moving parts.
  • the interplay between various optical phenomena results in higher transmission and polarization identification.
  • Preferred embodiments can be used for optimised spectro-polarization filters such as filters for multispectral color with polarization.
  • Embodiments can be achieved on a single platform of nanostructured metallic layer of nm thickness by exploiting optical phenomena through light matter interaction.
  • Metasurfaces in embodiments of the present invention are judicially positioned with respect to an imaging sensor's pixels so that when positioned over the imager and aligned with its pixels the filter controls individually and simultaneously the amplitude, color, and polarization of light being filtered color.
  • No other optic is known to be able to provide this versatility in manipulation of light fields.
  • plasmonic metasurfaces of embodiments of the present invention require only a single lithographic step to filter any wavelength while being significantly thinner and easier to fabricate as compared to competing technologies such as dichroic films or polymer dye filters.
  • dichroic filters multiple films of selective refractive index are required with the layer thickness dependent on the wavelength of light selected for filtering.
  • multiple lithographic steps are required with an additional coating to block infra-red light.
  • dye filters nor dichroic films are able to provide polarization selectivity.
  • metasurfaces according to embodiments of the present invention seek to overcome these obstacles and to provide significant degrees of freedom in comparison to current approaches.
  • metasurfaces can be integrated directly onto a CMOS camera pixel, single photon camera pixels and SPAD arrays.
  • CMOS camera pixel single photon camera pixels
  • SPAD arrays SPAD arrays.
  • embodiments seek to open up the potential for multispectral imaging and polarimetry without significant engineering or cost consequences.
  • Preferred embodiments enable creation of filters from one unit cell design of a plasmonic metasurface on a single layer that can be scaled from 450 nm to 2 pm (blue to SWIR regime).
  • This design requires a single lithographic step which makes it easy to manufacture into a pixelated format that can be directly integrated onto a camera chip. It is ultra-thin and has no moving parts.
  • the design also has high out-of-band rejection ratio for color selectivity and appreciable extinction ratio for orthogonal polarization states.
  • a unit cell refers to a common lattice arrangement of 8 nanoholes.
  • the dimensions, orientation and relative distances between the nanoholes may vary depending on frequency and polarization to be filtered.
  • Figure la is a schematic diagram of a plasmonic metasurface light filter according to an embodiment
  • Figure lb is a schematic plan view of a unit cell according to an embodiment
  • Figure lc is a cross-sectional view of part of a metasurface according to an embodiment
  • Figure Id is a schematic diagram illustrating integrating an embodiment with an imaging sensor
  • Figure 2 is a schematic diagram of a unit cell suitable for use in the embodiment of Figure 1;
  • Figure 3 is a schematic diagram of another unit cell suitable for use in the embodiment of Figure 1;
  • Figure 4 is a schematic diagram of another unit cell suitable for use in the embodiment of Figure 1;
  • Figures 5-8 are simulated transmission curves of the embodiments.
  • a single lithography layer plasmonic metasurface light filter is produced.
  • the metasurface of preferred embodiments has a low level of fabrication complexity and enables the manipulation of transmitted light for simultaneous wavelength selection and polarization control.
  • the metasurface design in preferred embodiments includes elliptical nanoholes etched into a nanometer thick metal layer.
  • the metasurface 10 includes a planar array of unit cells 20 (in this example the planar array is n x m unit cells).
  • Each unit cell 20 includes a plurality of light-transmissive nanoholes (discussed in more detail below) having a non-circular substantially elliptical cross-section.
  • Each unit cell is individually tunable with respect to frequency and polarization of light to filter by varying geometry of its respective nanoholes.
  • the arrows in the illustration show polarization angle being filtered - 0° (arrows top to bottom of cell), 90° (arrows left to right of cell), 45° (arrows bottom left to top right of cell) and 135° (arrows bottom right to top left of cell).
  • FIG. lb a plan view of a unit cell 20 according to an embodiment of the present invention is shown.
  • the unit cell includes elliptical nanoholes 30 having geometry that is varied at time of manufacture in dependence on the function of the particular unit cell so as to tune the filtering of the unit cell.
  • FIG. lc A cross-sectional view of part of a metasurface according to an embodiment is shown in Figure lc.
  • the substrate has a thickness of ⁇ 500 pm.
  • the metal layer of Aluminium has a thickness of 70 nm with a SiCh cap layer.
  • This diagram shows the cross-sectional view of the metasurface with the fused silica substrate. The light is incident through the substrate onto the metallic layer of aluminium which is covered by a cap layer of PECVD SiCh.
  • a UV resin glue could be used.
  • the metasurface is designed to take this into account - as can be seen in the cross sectional schematic where there is a glue layer over the cap layer.
  • Figure Id is a schematic diagram showing integration of a spectro-polarimeteric metasurface [005] onto an active sensing area of a camera chip [004] such that each pixel of the camera chip would be sensitive to a particular wavelength and polarization simultaneously.
  • the metasurface can be manufactured in a large area format [005] and integrated directly onto a camera chip [004], With this integration each pixel would see a particular wavelength and polarization of light giving it additional functionality rather than just intensity.
  • Figures 2-4 are schematic plan views of a unit cell according to various embodiments. These particular unit cells have been tuned so as to filter: green light (Metasurface filter -Green, MSF-G) and 90° polarization state (Figure 2); red light (Metasurface filter - Red, MSF-R) and 90° polarization state (Figure 3); blue light (Metasurface filter - Blue, MSF-B) for 90° polarization state ( Figure 4).
  • the size and spacing of the nanoholes dictate the frequency filtered while the orientation of the elliptical axes (which are the same for all nanoholes in the unit cell) dictates polarization filtering.
  • the unit cell comprises elliptical nanoholes [001] of dimensions A/6 and the ratio of 0.6.
  • Figure 5 shows the simulated transmission curves for the embodiment of Figure 2, with the peak transmission of 27.9% with a FWHM of 55 nm at A, pe ak 550 nm. Similar to MSF-B, the PER is efficient at -17.5 dB (170:1). The simulated transmission curves for the embodiment of Figure 3 are shown in Figure 6.
  • the transmission of this filter is 20.6% with a FWHM of 90 nm and X pea k at 648 nm.
  • the transmission of red is lower than blue and green due to the reduced effect of QCWs.
  • the arrangement of the nanoholes and their geometry in preferred embodiments enhances transmission of light through the generation of plasmons, and, advantageously, quasi-cylindrical waves (QCW) as well.
  • QCW quasi-cylindrical waves
  • metasurfaces according to preferred embodiments generate QCWs, which explains the increase in transmission when compared to completely plasmonic metallic films.
  • preferred embodiments show a higher transmission for a particular wavelength and polarization.
  • this device structure is compatible with all CMOS manufacturing technologies known to the inventors that is used for making chips for imagers.
  • QCWs are evanescent waves in the form of a Bessel function that arise from the coupling of the incident light with the guided mode confined in the nanoholes, from which they decay exponentially.
  • the total field scattered by the nanoholes at the interface is not a pure SPP mode, but incorporates a QCW traveling along the interface with the amplitude decaying with increasing distance away from the nanohole, namely x.
  • the decay of the QCW is much faster than that of the SPP for x > X.
  • the two waves almost equally contribute to the total field.
  • the fitting parameter, m denotes the decay of the Q.CW from the nanohole.
  • the change in phase due to the Q.CW is denoted by a.
  • a unit cell is the building block of the metasurface device and this is repeated throughout the area of concern in such a way to obtain the functionalities of that particular design and align unit cells to pixels when the filter is in place over the sensor (the mapping of unit cells to pixels may be 1:1 or many:l).
  • the geometry and period p of the unit cell may be modified to scale to any wavelength in the visible and SWIR spectrum (450 nm - 2 pm).
  • i and j are the diffraction orders which in this case is - (1,0).
  • the permittivities of the dielectric and metal layers are given as s ⁇ and s m , respectively.
  • a spp that changes the pea i ⁇ at which the EOT occurs.
  • p can be scaled to make the metasurface selective for any desired wavelength in the visible spectrum.
  • the dimensions of the elliptical nanoholes are modified as well..
  • Figure 7 shows the simulated transmission curves of the embodiment of Figure 4.
  • the unit cell depicted by [00x1] comprises of elliptical nanoholes of varying dimensions.
  • the period p was calculated as per Equation 3.
  • the dimensions of the elliptical nanoholes in [00x2] the ratio is 0.65 with b being approximately /6.
  • the dimensions of the elliptical nanoholes in [00x4] the ratio is 0.725 and b is approximately /5.5.
  • the dimensions of the elliptical nanoholes in [00x3] the ratio is 0.65 and b is approximately /7.
  • a spp is the dip before the EOT that occurs at A pea k at 473 nm with a full-width-half-maximum (FWHM) of 60 nm.
  • the orthogonal polarization (0°) is flat through the visible regime. A transmission efficiency of 28% was observed.
  • PER is the quantitative measure of the certainty of observing a polarization state.
  • the out-of -band rejection over the entire visible spectrum is high.
  • )) would exhibit polarization selectivity for any desired polarisation state.
  • the spectral overlap between the colors for a particular polarization is of importance. It is advantageous for imaging that a particular pixel detects with high certainty the color and polarization state of the designed metasurface integrated onto it, thus the spectral overlap (or cross talk) between various filters should be as low as possible.
  • the PER between the three colors of orthogonal polarization states is tabulated in Table 1. The table reads as the PER between the colors and polarization state (in the subscript) given in terms of dB.
  • the difference between two colors should be as high as possible and well above 50%. This is because the transmission intensity for the orthogonal pair of 45° and 135° will be 50% the value of 90°(as shown in Figure 7) for the same filtered color of light. In other words, the PER of any polarization state and color needs to be much larger than -3dB. Such that there is no discrepancy in detecting one particular color and polarization state.
  • embodiments have focused on visible light wavelengths and filtering. However, embodiments can also provide the same dual functionality (frequency and polarization filtering) for other wavelengths such as the SWIR regime. In such embodiments, the same design principles are used with the dimensions of the nanoholes scaled relative to the wavelength. However, annealed gold is substituted for aluminium and the nanoholes are formed in a nm thickness annealed gold layer.
  • NIR near infra-red
  • SWIR short wave infra-red

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Spectroscopy & Molecular Physics (AREA)
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Abstract

L'invention concerne un filtre de lumière à métasurface plasmonique. Le filtre de lumière comprend un réseau plan de cellules unitaires. Chaque cellule unitaire comprend une pluralité de nanotrous transmettant la lumière ayant une section transversale sensiblement elliptique non circulaire. Chaque cellule unitaire peut être réglée individuellement par rapport à la fréquence et à la polarisation de la lumière à filtrer en faisant varier la géométrie de ses nanotrous respectifs.
PCT/GB2023/050466 2022-03-01 2023-03-01 Filtre de lumière à métasurface plasmonique et capteur d'imagerie comprenant un filtre de lumière WO2023166289A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB2202821.1 2022-03-01
GB2202821.1A GB2616271A (en) 2022-03-01 2022-03-01 Plasmonic metasurface light filter
US17/936,095 2022-09-28
US17/936,095 US20230280498A1 (en) 2022-03-01 2022-09-28 Plasmonic metasurface light filter and Imaging Sensor including light filter

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WO2023166289A1 true WO2023166289A1 (fr) 2023-09-07

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Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
CARLOTA RUIZ DE GALARRETA ET AL: "Single-step fabrication of high performance extraordinary trans-mission plasmonic metasurfaces employing ultrafast lasers", ARXIV.ORG, CORNELL UNIVERSITY LIBRARY, 201 OLIN LIBRARY CORNELL UNIVERSITY ITHACA, NY 14853, 30 September 2021 (2021-09-30), XP091060754 *
SHAH YASH D ET AL: "Supporting Information: Ultra-narrow linewidth polarization-insensitive filter using a symmetry-breaking selective plasmonic metasurface [lambda]/nm Au thickness/nm Color Scale Title X Axis Title Color Scale Title", 12 December 2017 (2017-12-12), pages 38 - 47, XP093055757, Retrieved from the Internet <URL:https://pubs.acs.org/doi/suppl/10.1021/acsphotonics.7b01011/suppl_file/ph7b01011_si_003.pdf> [retrieved on 20230620] *
SHAH YASH D. ET AL: "Ultralow-light-level color image reconstruction using high-efficiency plasmonic metasurface mosaic filters", OPTICA, vol. 7, no. 6, 3 June 2020 (2020-06-03), pages 632, XP093055744, DOI: 10.1364/OPTICA.389905 *
SHAH YASH D. ET AL: "Ultra-narrow Line Width Polarization-Insensitive Filter Using a Symmetry-Breaking Selective Plasmonic Metasurface", ACS PHOTONICS, vol. 5, no. 2, 22 December 2017 (2017-12-22), pages 663 - 669, XP093055751, ISSN: 2330-4022, DOI: 10.1021/acsphotonics.7b01011 *

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