WO2013158842A1 - Réseau de cavités de cristal photonique - Google Patents

Réseau de cavités de cristal photonique Download PDF

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Publication number
WO2013158842A1
WO2013158842A1 PCT/US2013/037114 US2013037114W WO2013158842A1 WO 2013158842 A1 WO2013158842 A1 WO 2013158842A1 US 2013037114 W US2013037114 W US 2013037114W WO 2013158842 A1 WO2013158842 A1 WO 2013158842A1
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Prior art keywords
photonic crystal
optical
array
specified
dielectric
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PCT/US2013/037114
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English (en)
Inventor
Dirk Englund
Xuetao GAN
Ioannis Kymissis
Nadia Pervez
Original Assignee
Dirk Englund
Gan Xuetao
Ioannis Kymissis
Nadia Pervez
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Application filed by Dirk Englund, Gan Xuetao, Ioannis Kymissis, Nadia Pervez filed Critical Dirk Englund
Publication of WO2013158842A1 publication Critical patent/WO2013158842A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/126—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind using polarisation effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/12004—Combinations of two or more optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1225—Basic optical elements, e.g. light-guiding paths comprising photonic band-gap structures or photonic lattices
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
    • G02B6/29358—Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator
    • G02B6/29359—Cavity formed by light guide ends, e.g. fibre Fabry Pérot [FFP]

Definitions

  • Patent Application Serial No. 61/636,316 filed on April 20, 2012, and to U.S.
  • Optical spectrometers are devices that, when exposed to optical radiation, are able to 'read' the wavelengths of incident light and output a data set that can be used to tell a hardware device or a user the specific spectral content of that incident radiation. They can be used in a variety of applications, from academic to industrial settings, in research, design, or test applications. Generally, spectrometers rely on spectral separation of light via diffraction gratings, which is followed by detection via a coupled optical detector. Use of such gratings can involve extremely tight manufacturing tolerances, as well as extensive after-production qualification and calibration.
  • wavelengths of light then spatially separate downstream of this grating, and are generally measured by a linear detector array.
  • This spatially-resolved information is then converted to wavelength-resolved information using the geometry of the diffraction grating and the distance from the grating to the detector.
  • the distance from the grating to the detector is generally quite long, resulting in physically large spectrometers.
  • Photonic crystals can include periodic optical structures that can interact with visible light or other electromagnetic waves in a manner characterized by the structural specifics of the array, such as a lattice constant of a particular patterned region or element included in the array.
  • electromagnetic radiation When electromagnetic radiation is coupled into a substrate, without substrate modification, it can be waveguided to the end of the substrate uninhibited— much like it would in a fiber-optic cable.
  • photonic crystals when photonic crystals are patterned on the surface of this substrate, or a photonic crystal is coupled to the substrate, specific wavelength components of the light can be directed or scattered out of the surface of the substrate (e.g., extracted from the substrate).
  • the extracted wavelengths can include a wavelength distribution and spatial location defined by the photonic crystal structure.
  • An array of such photonic crystals can be used to provide a device that can emit light in spatially defined patterns that define or deterministically relate to an incoming spectrum of light propagating through the waveguiding substrate.
  • the outcoupled light extracted by the photonic crystal can be coupled to an imaging sensor or other optical detector, which can then record an image of the detected light pattern (including the intensity or wavelength of the detected light at various locations on the surface of the photonic crystal).
  • the information provided by the optical detector can be used to determine the incident radiation spectrum, or the presence and intensity of one or more specific ranges of wavelengths. Analysis of the images can then be performed via a computer or other electronics, such as including a processor configured to receive the information from the optical detector.
  • Modification of the array geometry included in a photonic crystal can alter the characteristics of optical energy that can be extracted from a photonic crystal including an array of periodic features.
  • a dielectric discontinuity can be included in the array of periodic features.
  • a photonic crystal including such a discontinuity can be referred to as a "cavity" structure though the dielectric discontinuity included in such a structure need not be a physical aperture or air void in the array of periodic features.
  • such a cavity can be a disruption in the periodicity of the array, such as including an omission of one or more array features.
  • An array of such photonic crystal cavities can provide high-resolution spectrometry across a broad spectral range with a low-cost, small- footprint apparatus (e.g., an integrated device).
  • respective cavities can be included in a two-dimensional (2D) planar photonic crystal (PPC) cavity array.
  • Such cavities can be patterned to be strongly selective at resonant modes spanning a spectrum of interest, such as spatially resolving incident light by dispersing its components across the 2D array of cavities.
  • a photonic crystal cavity array can be positioned on a 2D low-index waveguide of glass or polymer, or including one or more other materials, such as to facilitate coupling of light into the device.
  • a photonic crystal cavity array having a planar profile can be mated to commercially- available photodetectors, such as charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) photodetectors, such as enabling high-resolution spectroscopy in an extremely compact assembly.
  • CCDs charge-coupled devices
  • CMOS complementary metal-oxide-semiconductor
  • a spectrometer assembly including the photonic crystal cavity array can provide spectral analysis of incident light with resolution as high as the bandwidth of respective cavity modes. Accordingly, such cavity modes can be specified to include visible-to-deep-infrared spectral ranges, or one or more other ranges.
  • WDM optical communication systems can benefit from low-cost, small-footprint wavelength filtering made feasible by a compact spectrometer, such as allowing respective wavelength channels to be spatially de- multiplexed and detected.
  • an apparatus such as an integrated device or instrument, can include an optical waveguide and a photonic crystal included in or optically coupled to the optical waveguide.
  • the photonic crystal can include a first array of periodic features extending in two dimensions on or within the dielectric material, and a second array of periodic features extending in two dimensions on or within the dielectric material.
  • the first and second arrays of periodic features can include respective specified lattice constants and respective specified dielectric
  • Such a photonic crystal structure can be referred to as a photonic crystal cavity array or PPC cavity array.
  • Respective desired portions of propagating optical energy can be extracted from the waveguide through the photonic crystal, such as determined by the respective first and second specified lattice constants and the respective specified dielectric discontinuities.
  • the specified dielectric discontinuities can form a "cavity,” though such discontinuities need not be an aperture or air void.
  • FIG. 1A and FIG. IB illustrate generally views of an example that can include an optical waveguide and a photonic crystal.
  • FIG. 2 illustrates general an example that can include an optical waveguide, a photonic crystal, and an optical detector.
  • FIG. 3 illustrates generally an example that can include an optical waveguide and a photonic crystal.
  • FIG. 4 illustrates generally an example that can include an optical waveguide, a photonic crystal, and respective first and second detectors optically coupled to the photonic crystal.
  • FIG. 5 illustrates generally an illustrative example of a photonic crystal that can include a 3 x 3 (e.g., 9 element) cavity array, and a corresponding portion of the photonic crystal including an illustrative example of a cavity that can be included in the array.
  • 3 x 3 e.g., 9 element
  • FIG. 6 illustrates generally an illustrative example of detected optical energy from a cavity that can be included in a cavity array, such as corresponding to the illustrative example of FIG. 5.
  • FIG. 7 illustrates generally another illustrative example of detected optical energy from a cavity that can be included in a cavity array, such as corresponding to the example of FIG. 5.
  • FIG. 8 illustrates generally an illustrative example of optical energy that can be obtained from respective cavity structures included in respective portions of a cavity array, such as corresponding to the example of FIG. 5.
  • FIG. 9A illustrates generally an illustrative example of optical energy that can be obtained from respective cavity structures included in respective portions of a cavity array corresponding to the example of FIG. 5, such as when supplied with optical energy provided by a supercontinuum laser source.
  • FIG. 9B illustrates generally an illustrative example of optical energy that can be obtained from respective cavity structures included in respective portions of a cavity array corresponding to the example of FIG. 5, such as showing respective measurements obtained as each cavity structure included in the array is supplied with optical energy in a respective specified range of wavelengths corresponding to a fundamental mode resonance of respective cavities included in the array.
  • FIG. 10A illustrates generally an illustrative example of a photonic crystal that can include a 10 x 10 (e.g., 100 element) cavity array, such as can include a linear progression of center frequencies of respective resonant modes corresponding to respective cavity structures in the array.
  • 10 x 10 e.g., 100 element
  • FIG. 10B illustrates generally an illustrative example of an intensity band plotted with respect to wavelength for each cavity included in the array in the example of FIG. 10A, such as showing an approximately linear progression of intensity peaks for optical energy obtained reflected using respective cavities included in the array.
  • FIG. IOC illustrates generally an illustrative example that can include the reflected response of a photonic crystal including a cavity with a mode specified within a visible range of wavelengths.
  • FIG. 10D illustrates generally an illustrative example that can include the reflected response of photonic crystal including a cavity with a mode specified within a near- infrared range of wavelengths.
  • FIG. 11 illustrates generally a technique, such as a method, that can include forming a photonic crystal cavity array.
  • FIG. 12 illustrates generally a technique, such as method, that can include estimating a spectrum of detected optical energy that can be obtained from a photonic crystal cavity array.
  • Compact, stable, and economical spectrometers can be used for a wide variety of applications, such as wavelength division multiplexed optical communications, spectroscopic analysis of biochemical samples or processes, long-range detection.
  • planar spectrometers can use gratings patterned in a planar waveguide, micro-ring based devices, and superprisms in planar photonic crystals (PPCs). But, a technical challenge for such approaches can be the precise alignment related to sub- wavelength-scale optical waveguides.
  • a dielectric microsphere resonator on a two- dimensional (2D) multi-mode waveguide can be used.
  • coupling into the waveguide can be simpler, and such an approach can provide a resolution of about 0.01 nanometers (nm) at about 685 nm.
  • the small free spectral ranges of the resonators can limit a recoverable spectral range.
  • a much broader reproducible spectral range can be recovered via patterning a polymer layer to form a 2D photonic crystal grating on a low-index 2D waveguide.
  • such a polymer-layer 2D photonic crystal lacking the cavity structures described herein can be limited to approximately 40 nm over the visible range.
  • the present inventors have recognized, among other things, that such challenges can be reduced or overcome such as using a 2D array of high-quality- factor (Q) semiconductor photonic crystal nanocavities, such as positioned on a 2D low-index waveguide made of glass or polymer.
  • Q quality- factor
  • Such a 2D cavity array photonic crystal can be included as a portion of a compact spectrometer, such as shown and described in the examples below.
  • FIG. 1A and FIG. IB illustrate generally views of an example that can include an optical waveguide and a photonic crystal.
  • an apparatus 100 can include an optical waveguide 106 and a photonic crystal 102 included as a portion of the optical waveguide 106 or optically coupled to the optical waveguide 106.
  • the photonic crystal 102 can include a first region
  • first and second regions 120 A or 120B can include respective lattice constants, such as a first lattice constant, "a,” or a second lattice constant, "b,” as shown in the example of FIG. 1A and IB.
  • the feature 190 can penetrate into the photonic crystal 102 or protrude out.
  • the feature 190 can penetrate nearly entirely through or entirely through a depth of the photonic crystal 102.
  • the waveguide 106 can be adhered to the photonic crystal 102, such as to provide mechanical support or to transfer the photonic crystal 102.
  • One or more of the optical waveguide 106 or the photonic crystal 102 can be a substrate or can provide mechanical support for other structures, or the optical waveguide 106 or photonic crystal 102 can be coupled to a mechanical support.
  • the photonic crystal 102 can include a first dielectric material, and one or more features included in the first or second regions 120A or 120B (or elsewhere) can provide a dielectric "contrast," such as including a different second dielectric material (either a void or a second material coupled to the photonic crystal 102).
  • the photonic crystal can be imprinted or stamped to provide the patterns in the first or second regions 120 A or 120B, and a stamp can remain coupled to the photonic crystal such as after imprinting.
  • a periodic potential formed by spatial variation in the relative permittivity " ⁇ ⁇ " of a medium can interact with electromagnetic radiation resulting in partial or complete photonic bandgaps.
  • the band structure can be determined by one or more of the choice of lattice, the basis formed by the shape and size of the holes (or bars, since an effective permittivity contrast or variation is desired), the thickness of a patterned layer, or the contrast in the spatial variation of the permittivity, "3 ⁇ 4 "
  • the energy scale for the band structure can be determined by a lattice constant and the permittivity (or index of refraction).
  • the periodicity of the array can be described by a lattice constant indicative of the spacing between adjacent like lattice site regions in the periodic lattice, such as the illustrative example of the first lattice constant "a " corresponding to the first region 120 A, and the second lattice constant "b" corresponding to the second region 120B.
  • the lattice constant can determine the wavelength or wavelengths of electromagnetic outcoupling, such as to extract a first range of wavelengths 170A using the first region 120A of the photonic crystal 102.
  • a second range of wavelengths 170B can be extracted from the incoming optical energy 110 using a second region 120B of the photonic crystal 102.
  • a periodic transverse potential can exist in proximity to the perimeter of the waveguide 106, such as within or even slightly beyond a cladding material surrounding the waveguide (or air, if the waveguide is not clad).
  • the transverse component of the wavevector corresponding to the optical energy 110 propagating through the waveguide can be scattered by a reciprocal lattice vector provided by the photonic crystal 102, allowing the photonic crystal to extract a desired portion of the optical energy from the waveguide within a specified (e.g., desired) range of wavelengths, determined at least in part by the lattice constant.
  • the basis and the index of refraction of the material in which the photonic crystal pattern is formed can determine the strength of this wavelength-selective outcoupling, such as when the crystal pattern presents a contrasting effective permittivity as compared to other regions surrounding the waveguide 106.
  • a complete photonic bandgap can be avoided in the ranges of wavelengths of interest, such as to avoid entirely disrupting propagation within the waveguide 106, or to avoid strongly coupling guided modes out of the waveguide 106.
  • a partial bandgap can be provided, such as by adjusting one or more of a depth or fill factor of individual cavities, bars, or apertures included in the periodic array, or by adjusting the lattice pattern (e.g., using a hexagonal pattern, a square pattern, or one or more patterns), such as in the first or second regions 120A-B, resulting in weak coupling (e.g., "leaky mode coupling") of the optical energy 110 in the desired ranges of wavelengths provided by the first and second regions 120A-B of the photonic crystal 102.
  • weak coupling e.g., "leaky mode coupling
  • the photonic crystal 102 can be made thin with respect to the waveguide, such as to perturb a boundary field distribution around the waveguide 106.
  • the fill factor can be represented as "r/a,” where the "r” is the radius of a round cavity included in the array, and "a” is the lattice constant.
  • an array of such patterns can be used to create spatially-resolved wavelength-selective outcoupling, which can then be directed toward an optical detector.
  • One or more of the waveguide 106 or photonic crystal 102 can be made of polycarbonate, Poly(methyl methacrylate) ("PMMA”), epoxy, glass, quartz, or fused silica, among others.
  • the waveguide 106 can include polydimethylsiloxane (PDMS), and the photonic crystal 102 can include a semiconductor material such as Gallium Phosphide (GaP).
  • PDMS polydimethylsiloxane
  • GaP Gallium Phosphide
  • the PDMS or other material comprising the waveguide 106 can be more flexible that the photonic crystal 102, for example.
  • the present inventors have recognized, among other things, that including a dielectric discontinuity in respective arrays of features, such as a first dielectric discontinuity 180A or a second dielectric discontinuity 180B, can increase a quality factor of a resonant mode of a corresponding portion of the photonic crystal structure, as compared to an array of periodic features lacking the dielectric discontinuity 180A or 180B.
  • Such an increased quality factor can provide increased outcoupling efficiency, or can allow higher resolution by providing more closely- spaced modes of respective arrays included in the photonic crystal 102, such as shown in the illustrative examples of FIGS. 5 and 10A, for example.
  • Such a dielectric discontinuity in combination with the array of periodic features, can be referred to as a photonic crystal "cavity” or “nanocavity,” with the prefix “nano” generally referring to the small dimensions attainable by such structures.
  • a region 120 A including the array of periodic features and the dielectric discontinuity can be on the order of about ten
  • a photonic crystal including a large number of respective arrays of periodic features having differing lattice constants can be used to provide a hundreds, thousands, or even millions of wavelength channels that can be contemporaneously monitored.
  • PPC planar photonic crystal
  • FIG. 2 illustrates general an example that can include an optical waveguide
  • the photonic crystal 202 can include respective regions such as a first region 220A or a second region 220B, such as can include respective periodic arrays of features.
  • the first or second regions 220A or 220B can include respective dielectric discontinuities, such as to provide a respective photonic crystal cavity structure in the first region 220 A or the second region 220B.
  • Optical energy 210 can be coupled to a portion 208 of the waveguide, such as using one or more of a lensing system or a fiber optic structure, for example.
  • the photonic crystal 202 can outcouple (e.g., scatter) or otherwise extract portions of the optical energy 210, such as coupling such extracted optical energy to the optical detector 224 using a coupling region 222.
  • portions of the apparatus 200 can include an integrated device such as fabricated using one or more integrated circuit fabrication techniques and the coupling region 222 can include a dielectric slab, polarizer, optical coupling bundle, or one or more other optical structures.
  • the optical detector 224 can include optical imaging detectors such as one or more of a charge-coupled device ("CCD"), a complementary-metal-oxide- semiconductor (“CMOS”) image detector, or one or more other optical detectors, such as can be coupled to a processor circuit 226.
  • the processor circuit 226 can receive information detected by the optical detector 224. The information can be indicative of one or more of the position, intensity, or wavelength of optical energy detected by the optical detector 224.
  • the processor 226 can be configured to provide an estimate of the spectrum of the incident optical energy 210 at least in part using the information provided by the optical detector 224.
  • the apparatus 200 can include a mechanical transducer 212 mechanically coupled to the optical waveguide 206 or other portion of the apparatus 200.
  • the mechanical transducer can include a piezoelectric material, such as lead zirconate titanate (PZT), or one or more other materials, such as to adjust (e.g., mechanically modulate) one or more of a first or second specified lattice constant to select a range of optical frequencies to be extracted by the photonic crystal from the optical waveguide, or to mechanically position a portion of the apparatus 200 for alignment or readout of a portion of the photonic crystal 202, such as shown in the example of FIG. 4.
  • PZT lead zirconate titanate
  • FIG. 3 illustrates generally an example of an apparatus 300 that can include an optical waveguide 306 and a photonic crystal 302.
  • incident optical energy 310 which can be referred to as "probe light”
  • the waveguide is transparent with respect to a range of frequencies of interest.
  • the waveguided optical energy can then be coupled into respective photonic crystal cavity modes corresponding to respective regions of the photonic crystal cavity array 302.
  • a portion of the waveguided optical energy can be transmitted out of plane with a strong (e.g., "narrowband" signal), such as selectively outcoupled at a resonant mode of a corresponding portion of the cavity array.
  • the optical energy is dispersed into a 2D spatial array of photonic crystal cavity structures that can span the spectrum of the incident optical energy and scattered optical energy from respective cavities can be used to determine the spectral content of the optical energy 310.
  • spectral resolution can be enhanced such as using a quality factor (Q) of respective photonic crystal cavities in low-loss semiconductors, such as compared to other materials or using photonic crystals lacking such cavity structures.
  • Q quality factor
  • a quality factor of photonic crystal cavity structure can be as high as 10 6 or more, and a resolution can be represented by " ⁇ ,” such as about 1.5 picometers (pm) or less, such as at a wavelength, " ⁇ ," of about 1.5 ⁇ .
  • FIG. 4 illustrates generally an example that can include an optical waveguide 406, a photonic crystal 402, and respective first and second detectors 424A and 424B that can be optically coupled to the photonic crystal 402.
  • the apparatus 400 of FIG. 4 can be used to obtain information indicative of the performance of one or more photonic crystals included in a photonic crystal cavity array, such as information shown in the illustrative examples of FIGS. 6-8, or 10C-10D.
  • an objective lens 460 can be used to focus optical energy from a specified region of the photonic crystal 402 for delivery to one or more of the first or second optical detectors 424 A or 424B.
  • a polarizer 464 can be included in the optical pathway between the photonic crystal 402 and the first or second detectors 424A or 424B, such as to provide polarization-selective detection of scattered optical energy outcoupled from the waveguide 406 using the photonic crystal 402.
  • An optical source 462 such as a supercontinuum laser
  • the supercontinuum laser can have a wavelength range of 0.55 ⁇ -1.2 ⁇ , such as can be coupled into the optical waveguide 406, filtered by the cavities in the photonic crystal 420 into respective spatially-separated narrowband signals, which can then be detected using the first or second detectors 424A or 424B.
  • a flipped mirror 466 or splitter can be used to selectively or jointly trasnfer the outcoupled optical energy to one or more of the first or second detectors 424A or 424B, such as a using a first lens 470A or a second lens 470B, or other optics.
  • the first detector 424A can include a spectrometer or other imaging or detection apparatus
  • the second detector 424B can include a photodiode or other imaging or detection apparatus
  • a stage 412 can include a mechanical transducer, such as a piezoelectric transducer (e.g., including PZT), such as to mechanically scan or position the photonic crystal 402.
  • FIG. 5 illustrates generally an illustrative example of a photonic crystal that can include a 3 x 3 (e.g., 9 element) cavity array 520, and a corresponding portion of the photonic crystal including an illustrative example of a cavity 520A that can be included in the array.
  • respective cavities in the array can include respective periodic arrays of features, and respective dielectric discontinuities, such as a dielectric discontinuity 580 within a respective periodic array of features.
  • the discontinuity 580 can include a linear three-hole (L3) "defect," and one or more adjacent “holes” can be slightly shifted, such as shown in the example of FIG. 5.
  • a photonic crystal cavity array can be formed in a semiconductor material such as gallium phosphide (GaP), or one or more other materials, and the PPC cavity array can be coupled to a semiconductor material such as gallium phosphide (GaP), or one or more other materials, and the PPC cavity array can be coupled to a semiconductor material such as gallium phosphide (GaP), or one or more other materials, and the PPC cavity array can be coupled to a semiconductor material such as gallium phosphide (GaP), or one or more other materials, and the PPC cavity array can be coupled to a semiconductor material such as gallium phosphide (GaP), or one or more other materials, and the PPC cavity array can be coupled to a semiconductor material such as gallium phosphide (GaP), or one or more other materials, and the PPC cavity array can be coupled to a semiconductor material such as gallium phosphide (GaP), or one or more other materials, and the PPC cavity array can be
  • Such an assembly can provide a resolution, ⁇ , of about 0.3 nm, such as at a wavelength, ⁇ , of about 840 nm.
  • a technique for making the photonic crystal cavity array 520 can include using electron-beam lithography, dry etching, and wet chemical undercutting of an Aluminum Gallium Phosphide (AlGaP) sacrificial layer to provide the photonic crystal cavity array in a about a 138-nm-thick GaP membrane.
  • AlGaP Aluminum Gallium Phosphide
  • such an array 520 can include an array of 3 x 3 (e.g., nine) cavities with a pitch of about 3 ⁇ , such as shown in FIG. 5, or such an array 520 can include a much larger number of respective photonic crystal cavity structures, such as shown FIG. 10A.
  • an air-hole size in each cavity region of the array can be increased with a scaled exposure dosage during an electron-beam lithography operation, such as resulting in a blue-shift of the cavity resonances across the array.
  • One or more trenches, such as a trench 590 can be included around a photonic crystal cavity array 520 edge, such as to enable easy pick-up and transfer, such as using a PDMS stamping technique.
  • such a PDMS stamp can include thickness of 120 micrometers ( ⁇ ), such as for use in transferring the cavity array, or which can also function as a waveguide, such as after suspension across a mechanical support.
  • FIG. 6 illustrates generally an illustrative example of detected optical energy that can be obtained from a cavity that can be included in a cavity array, such as corresponding to the illustrative example of FIG. 5.
  • the dashed and solid lines represent respective experimentally-obtained examples that can be acquired before and after a 90-degree rotation of a polarizer, such as discussed above in the example of FIG. 4.
  • the inset portion of FIG. 6 illustrates generally a Lorentzian fit to a fundamental resonant mode of a respective cavity.
  • the spectra shown in FIG. 6 represent a normalized intensity (e.g., in "arbitrary units" or "a.u.”).
  • FIG. 7 illustrates generally an illustrative example of a normalized optical energy reflected by cavity that can be included in a cavity array, such as
  • the reflected optical energy can be experimentally obtained, such as corresponding to a cavity (5) in the illustrative example of FIG. 5.
  • a supercontinuum laser source with wavelength range of 0.55 ⁇ -1.2 ⁇ can be edge-coupled into a PDMS waveguide, such as via a single mode fiber, and scattered light from the cavity array can be collected such as using a confocal microscope with a lOOx objective lens (e.g., including a numerical aperture (NA) of about 0.95), such as shown in the illustrative example of FIG. 4.
  • a spectral response of the scattered light from cavities can be detected using a commercially- available spectrometer.
  • FIG. 6 illustrates generally experimentally-obtained scattered spectra that can be obtained from cavity (5) of FIG. 5. The scattered spectra shown in FIG.
  • the Lorentzian fit to a peak at about 833.8 nm yields a Q factor of about 3,400, such as corresponding to a fundamental mode of the L3 cavity.
  • Such cavity modes can be verified by a vertical reflectivity measurement, such as can be performed using a cross-polarized microscope configuration.
  • the experimentally-obtained reflected spectrum in FIG. 7 includes similar resonance peaks and Q factors as the scattered spectra experimentally obtained under the 2D- waveguide excitation.
  • the other eight cavities can also provide corresponding resonant modes in scattering, as can be shown in measurements, such as included in the illustrative example of FIG. 8.
  • FIG. 8 illustrates generally an illustrative example of optical energy that can be obtained from respective cavity structures included in respective portions of a cavity array, such as corresponding to the example of FIG. 5.
  • the scattered spectra shown in FIG. 8 can respectively correspond to the nine cavities included in FIG. 5, such as including fundamental modes at about 840.8 nm, about 838.5 nm, about 841.1 nm, about 842.6 nm, about 833.8 nm, about 844.2 nm, about 845.7 nm, about 844.5 nm, and about 846.9 nm.
  • These modes include peaks with ratios of roughly 10 to the background and Q factors in the range of about 2,500- 3,500, which indicates that cavities in the array can function as respective filters with respective bandwidths less than about 0.34 nm.
  • FIG. 9A illustrates generally an illustrative example of optical energy that can be obtained from respective cavity structures included in respective portions of a cavity array 520 corresponding to the example of FIG. 5, such as when supplied with optical energy provided by a supercontinuum laser source
  • FIG. 9B illustrates generally an illustrative example of optical energy that can be obtained from respective cavity structures included in respective portions of a cavity array corresponding to the example of FIG. 5, such as showing respective measurements obtained as each cavity structure included in the array is supplied with filtered optical energy in a respective specified range of wavelengths corresponding to a fundamental mode resonance of respective cavities included in the array.
  • FIGS. 9A and 9B can be referred to as "scanning maps," and a spatial distribution of optical energy scattered by respective cavity structures in a photonic crystal can be mechanically scanned to obtain such maps.
  • apparatus such as shown in FIG. 4 can be used, such as including using a piezoelectric stage with a step of about 100 nm while recording corresponding optical energy extracted from the waveguide by the photonic crystal cavity.
  • Such recording can include using a photodiode.
  • FIG. 9 A shows an illustrative example of transmitted-light can be experimentally obtained when the cavity array is illuminated with an edge-coupled supercontinuum laser.
  • Nine bright spots are visible and generally match the L3 photonic crystal cavity locations as expected.
  • the spectrally-resolved measurements can be performed over the same physical locations of cavities confirming that the highest intensity in each of the bright spots of FIG. 9A corresponds to a respective cavity fundamental mode.
  • monochromatic inputs to the waveguide can be provided such as by spectrally filtering the supercontinuum light with bandwidth of about 0.3 nm to analyze the spatially resolved spectral filtering characteristics of the cavity array. For example, nine spatially-resolved
  • FIG. 9B illustrates generally experimentally-obtained results where the nine scanned regions are arranged in the order of the cavities (1-9) as shown in FIG. 5.
  • the cavity whose fundamental mode matches the probe light generally exhibits a bright spot with high contrast from other cavity regions, which illustrates generally the functioning of the cavities as wavelength-selective channels that can spatially-separate respective wavelengths into different areas along the surface of the photonic crystal cavity array.
  • the 844.5 nm input with a bandwidth of 0.3 nm is extracted strongly by the fundamental mode of cavity 8, some of the light can overlap in wavelength with the fundamental mode of cavity 6 and can therefore also extracted by cavity 6.
  • such experimentally- obtained scanning results of narrow-band light sources demonstrate that the cavity array spectrometer can enable a resolution about as high as the bandwidth of the respective cavity modes.
  • FIG. 10A illustrates generally an illustrative example of a microscope image of a photonic crystal that can include a 10 x 10 (e.g., 100 element) cavity array, such as can include a linear progression of center frequencies of respective resonant modes corresponding to respective cavity structures in the array.
  • Respective cavities such as a first cavity 1002 can include respective fundamental mode wavelengths that provide a linear progression of modes.
  • FIG. 10B illustrates generally an illustrative example of an intensity band plotted with respect to wavelength for each cavity included in the array in the example of FIG. 10A, such as showing an approximately linear progression of intensity peaks for respective cavities included in the array.
  • FIG. 10B generally shows a wavelength range of coverage from about 805 nm to about 840 nm, along with selected spectra that can be obtained from 1st, 35th, and 95th cavities in the array, respectively.
  • FIG. IOC illustrates generally an illustrative example that can include the reflected response of a photonic crystal including a cavity with a mode specified within a visible range of wavelengths, along with a Lorentzian fit to the fundamental mode, such as can be used to estimate a quality factor for the cavity.
  • FIG. 10D illustrates generally an illustrative example that can include the reflected response of photonic crystal including a cavity with a mode specified within a near- infrared range of wavelengths, with a Lorentzian fit to the
  • fundamental mode such as can be used to estimate a quality factor for the cavity.
  • the resonant wavelengths of the cavities in the array can be varied linearly, such as to cover an entirety of a wavelength range of interest of the target source.
  • Control of the channel peak wavelength and resolution can be provided such as by
  • the recoverable spectral range Another parameter for the spectrometer is the recoverable spectral range.
  • the scattering behavior of a fundamental mode of respective cavities can be nearly ten times higher above the background, as shown in the illustrative example of FIG. 6, transmission at higher order modes can complicate spectral recovery.
  • the recoverable spectral range can be determined at least in part by a spectral separation between the higher order and fundamental modes of an L3 cavity, which is generally about 5% of the resonant wavelength of the fundamental mode.
  • the illustrative example of FIG. 10A includes a 10 xlO cavity array having swept hole sizes and respective L3 defects.
  • An experimentally-obtained cross- polarized reflectivity measurement is shown in the illustrative example of FIG. 10B, such as indicating that the cavities of FIG. 10A can include resonant modes with the same spaced wavelength shift of about 0.35 nm around 820 nm, without background from higher order modes.
  • the illustrative example of the cavity array of FIG. 10A can be used to resolve an input spectrum from about 805 nm to about 840 nm, which can be covered by the free spectral range of the L3 cavities in this wavelength range.
  • the illustrative example of FIG. 10A includes a GaP photonic crystal.
  • cavities can be densely integrated into an array, the cavities respectively including a high Q factor and precisely controlled resonant modes. This improves not only the resolution, but can create wavelength- selective channels that are small enough in area so as can be matched with high resolution commercially-available detectors, such as on a pixel- by-pixel basis.
  • a successful transfer of a PPC membrane with dimensions of 425x425 ⁇ or more can be achieved, providing sufficient area for an array including a significant number of cavity regions.
  • FIG. 11 illustrates generally a technique 1100, such as a method, that can include forming a photonic crystal cavity array.
  • an optical waveguide can be formed.
  • a photonic crystal can be included in or coupled to the optical waveguide.
  • the photonic crystal can be formed in the optical waveguide, or the photonic crystal can be formed and coupled to the optical waveguide.
  • FIG. 12 illustrates generally a technique 1200, such as method, that can include estimating a spectrum of detected optical energy that can be obtained from a photonic crystal cavity array.
  • optical energy can be coupled to an optical waveguide.
  • portions of the optical energy can be extracted from the waveguide, such as using respective photonic crystal cavity regions to extract respective wavelengths ranges of the optical energy.
  • the optical energy extracted by the photonic crystal can be detected.
  • a spectrum can be estimated corresponding to the incident optical energy provided to the waveguide, such as using information about a spatial location or intensity of the detected optical energy obtained from the respective photonic crystal cavity regions.
  • Method examples described herein can be machine or computer- implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples.
  • An implementation of such methods can include code, such as microcode, assembly language code, a higher- level language code, or the like. Such code can include computer readable instructions for performing various methods.
  • the code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or nonvolatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.
  • RAMs random access memories
  • ROMs read only memories

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Abstract

L'invention concerne un appareil, tel qu'un dispositif ou un instrument intégré, pouvant comprendre un guide d'onde optique et un cristal photonique compris dans le guide d'onde optique ou accouplé optiquement à celui-ci. Le cristal photonique peut comprendre un premier réseau de caractéristiques périodiques s'étendant dans deux dimensions sur ou dans le matériau diélectrique, et un deuxième réseau de caractéristiques périodiques s'étendant dans deux dimensions sur ou dans le matériau diélectrique. Les premier et deuxième réseaux de caractéristiques périodiques peuvent avoir des constantes de réseau spécifiées respectives et des discontinuités diélectriques spécifiées respectives dans les premier et deuxième réseaux de caractéristiques périodiques. Des parties souhaitées respectives d'énergie optique se propageant peuvent être extraites du guide d'onde par le cristal photonique, telles que celles déterminées par les première et deuxième constantes de réseau spécifiées respectives et les discontinuités diélectriques spécifiées respectives. Les discontinuités diélectriques spécifiées peuvent être appelées cavités, bien que ces discontinuités ne soient pas nécessairement une ouverture ou un creux.
PCT/US2013/037114 2012-04-20 2013-04-18 Réseau de cavités de cristal photonique WO2013158842A1 (fr)

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US8854624B2 (en) 2009-10-12 2014-10-07 The Trustees Of Columbia University In The City Of New York Photonic crystal spectrometer
US10656013B2 (en) 2015-09-29 2020-05-19 Chromation Inc. Nanostructure based article, optical sensor and analytical instrument and method of forming same
US10859437B2 (en) 2016-05-10 2020-12-08 Chromation, Inc. Integration of optical components within a folded optical path
CN117784291A (zh) * 2023-12-26 2024-03-29 北京信息科技大学 一种基于光子晶体的宽谱段多光谱超表面及测试系统

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US7440658B2 (en) * 2004-03-03 2008-10-21 Japan Science And Technology Agency Photonic crystal coupling defect waveguide
US7483466B2 (en) * 2005-04-28 2009-01-27 Canon Kabushiki Kaisha Vertical cavity surface emitting laser device
WO2011046875A1 (fr) * 2009-10-12 2011-04-21 Nadia Pervez Spectromètre à cristal photonique

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US7483466B2 (en) * 2005-04-28 2009-01-27 Canon Kabushiki Kaisha Vertical cavity surface emitting laser device
WO2011046875A1 (fr) * 2009-10-12 2011-04-21 Nadia Pervez Spectromètre à cristal photonique
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Publication number Priority date Publication date Assignee Title
US8854624B2 (en) 2009-10-12 2014-10-07 The Trustees Of Columbia University In The City Of New York Photonic crystal spectrometer
US9366571B2 (en) 2009-10-12 2016-06-14 The Trustees Of Columbia University In The City Of New York Photonic crystal sensor apparatus and techniques
US10656013B2 (en) 2015-09-29 2020-05-19 Chromation Inc. Nanostructure based article, optical sensor and analytical instrument and method of forming same
US11255727B2 (en) 2015-09-29 2022-02-22 Chromation Inc. Nanostructure based article, optical sensor and analytical instrument and method of forming same
US10859437B2 (en) 2016-05-10 2020-12-08 Chromation, Inc. Integration of optical components within a folded optical path
US11353362B2 (en) 2016-05-10 2022-06-07 Chromation Inc. Integration of optical components within a folded optical path
CN117784291A (zh) * 2023-12-26 2024-03-29 北京信息科技大学 一种基于光子晶体的宽谱段多光谱超表面及测试系统

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