This PDF file contains the front matter associated with SPIE Proceedings Volume 7609, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We study the influence of the mechanical deformation induced by a surface acoustic wave (SAW) on the resonance frequency of a defect cavity in a 2D photonic crystal membrane. Using FDTD-simulations we determine the resonance frequency and quality factor of a nanocavity of a GaAs based structure with embedded InAs quantum dots. Under the influence of a SAW, we find a periodic modulation of the cavity resonance wavelength of Δλ >2 nm accompanied by only a weak < 0.5× reduction of the Q-factor. Initial experiments for a SAW wavelength of ~ 1.8μm show a pronounced broadening of the time-integrated cavity emission line corresponding to a shift of ≥ 1 nm.

Light emission at 1.54 μm from an Er-doped amorphous silicon nitride layer coupled to photonic crystal resonators and plamonic arrays is studied. We observe the cavity resonances at cryogenic and room temperatures and under varying optical pump powers. The results demonstrate that small mode volume, high quality factor resonators enhance Er absorption rates dramatically at the cavity resonance. Photonic crystal cavity resonances exhibit linewidth narrowing with pump power at cryogenic temperatures, signifying absorption bleaching and partial inversion of the Er ions. In addition, we fabricate periodic metal-insulator-metal plasmonic structures with a simple bottom-up fabrication technique. We observe a factor of 10 increase of Er emission coupled to plasmonic structures.

We propose and demonstrate a hybrid cavity system in which metal nanoparticles are evanescently coupled to a dielectric photonic crystal cavity using a nanoassembly method. While the metal constituents lead to strongly localized fields, optical feedback is provided by the surrounding photonic crystal structure. The combined effect of plasmonic field enhancement and high quality factor (Q ≈ 900) opens new routes for the control of light-matter interaction at the nanoscale.

We report direct measurement of spectrally selective absorption properties of PbSe and PbS colloidal quantum dots (CQDs) in Si nanomembrane photonic crystal cavities on flexible polyethylene terephthalate (PET) substrates. Enhanced optical absorption was obtained when CQD absorption overlaps with photonic crystal Fano resonances. On the other hand, no absorption was observed when the Fano resonance has no spectral overlap with the CQD absorption bands. The measurement results agree well with the simulation results obtained based on 3D FDTD and RCWA simulation techniques. Measured angular and polarization properties also agree well with Fano resonance transmission properties, which were obtained experimentally and, theoretically based on simulated dispersion properties and transmission properties. Bending induced spectral shifts were characterized for potentially flexible photonic device applications.

A theory is presented for the quantum radiation emitted from a single exciton in a quantum dot. We assume that the quantum dot is in strong coupling to a slab photonic crystal cavity. A dielectric function of spatial coordinates is used to explain the effects of the macroscopic medium. It has been proved that the electric field in such a medium can be described using the so-called K-function. We derive a formula for obtaining the frequency spectrum, and present an analytical result for the optical spectrum, which is dependent on the K-function. We also have considered a slab photonic crystal configuration with hexagonal structure containing a cavity to evaluate the frequency spectrum in such a medium. FDTD method has been used to calculate the generalized-transverse green function and the K-function everywhere in the medium.

We present L-I, I-V and spectral characteristics at 300 and 77 K of the flip-chip LED arrays based on p-InAsSbP/n- InGaAsSb heterostrucutres with photonic crystal formed onto an outcoupling n⁺-InAs substrate. We also describe results on IR imaging (2D radiation mapping) and near and far field patterns in forward biased LEDs.

We report the demonstration of a cascaded configuration to realize wideband high-resolution spectrometers in silicon-nitride for the visible range. The cascaded configuration consists of an arrayed waveguide grating followed by a set of resonators and offers a flexibility to achieve the requirements of different sensing applications. We discuss some of the implementation issues of these structures. A preliminary demonstration shows the capability of such spectrometer devices to achieve ~0.1 nm wavelength resolution over 10 nm bandwidth in a compact device in a mm-scale device.

In this paper, we present both numerical and experimental results for the waveguiding of light using a low-index-contrast (LIC) self-collimating photonic crystal (SCPhC) in the RF frequency regime. This waveguiding structure utilizes the unique interactions of light with the periodic structure of the photonic crystal (PhC) to propagate a beam of light without divergence. This design also employs materials with a low index contrast (LIC), which reduces the electromagnetic signature of the PhC. This SCPhC was designed by extracting its dispersion contours and numerically simulating it using HFSS, a commercial 3-D, full-wave FEM software. In particular, we addressed the issue of coupling the PhC to a coaxial medium by designing an input/output (I/O) coupler consisting of a coaxial-to-waveguide transition, a rectangular waveguide and a tapered dielectric transition. We fabricated the SCPhC with a rigid polyurethane foam slab and Rexolite polystyrene rods using an automated CNC router to drill the periodic lattice in the slab. We also fabricated the dielectric segments of the I/O couplers with Rexolite slabs using an automated milling machine. Using these I/O couplers and SCPhC slab, we simulated and subsequently measured experimentally an insertion loss, for the entire system, of -3.3 dB through a 24" PhC slab, and a coupling loss of -0.95 dB at each coupler-PhC interface.

We present and discuss several of the benefits associated with using chip-scale optical interconnects in reconfigurable computing systems. As is well known, by removing metallic traces in high-speed systems, many signal integrity issues are reduced, or eliminated, e.g., parasitic capacitance and inductance associated self-induced affects and trace overlay. In addition, photonic systems can require less power and offer higher efficiency, thereby, giving rise to reduced thermal energy dissipation. However, at least in the case of reconfigurable processors there are several additional advantages. A case in point is that of field programmable gate arrays (FPGAs), which is a technology that has been plagued by interconnect limitations. To address this, we have developed an interconnect network that will enable fully reconfigurable processors, or FPGAs. Our approach is based on a photonic crystal cross-bar switch that enables complete interconnectivity over large computational-block arrays. Perhaps one of the most attractive benefits of our approach is that it alleviates the need to perform place and route during processor layout. As such, our approach may allow for reconfigurable processors consisting of a higher density of computing-blocks along with a faster interconnect medium. Accordingly, this talk will present numerical studies, design and fabrication of various implementations of candidate photonic crystal devices for reconfigurable optically interconnected chip-scale networks.

Based on the self-collimation effect of light propagating inside a photonic crystal, we demonstrate a novel concept for a compact Mach-Zehnder interferometer. The properties of these self-collimated beams are such that we can manipulate them to form the beam splitters and mirrors of the Mach-Zehnder interferometer in a very compact area of 20x20 μm². We obtain the unidirectional output behaviour characterized by the high contrast in the telecommunication-wavelength signal at the two outputs of the photonic crystal Mach-Zehnder interferometer. The experiments are done using optical transmission spectroscopy and far-field optical microscopy. This photonic crystal Mach-Zehnder interferometer holds a promise for a compact Mach-Zehnder modulator, inspired by recent reports of NEMS-based photonic crystal membrane.

In this paper we demonstrate an approach for laser holographic manufacturing of three-dimensional photonic lattice structures using a single specially designed, diffraction optical element mask. The mask is fabricated by recording gratings in a photosensitive polymer using a two-beam interference method and has four diffraction gratings in the sample plane, with a same distance from the opening center and oriented four-fold symmetrically. Four first-order diffracted beams by the gratings and one non-diffracted central beam overlap and form three-dimensional interference pattern. The phase of one side beam is delayed by inserting a thin piece of microscope glass slide into the beam. By rotating the glass slide thus tuning the phase of the side beam, the five beam interference pattern changes from facecenter tetragonal symmetry into desired diamond-like lattice symmetry. The three-dimensional interference pattern is recorded in a photosensitive polymer, showing the phase tuning related changes of photonic lattice structures. Combing an amplitude mask with the phase mask by putting the amplitude mask in the central opening of the diffraction optical element mask, line defects are produced within the photonic crystal template.

A complete photonic band gap inhibits light propagation in all directions regardless of the polarization. This likely provides a means of molding light at the level of physical limits. For example, a complete PBG can be applied to construct nanocavities with ultra-high quality (Q) factor while maintaining a small mode volume, and low-loss waveguide. These are useful for the applications, such as thresholdless lasers, nonlinear optics and 3D optics. Only three-dimensional (3D) photonic crystals can possess a complete band gap. However, the application of 3D photonic crystal is restricted because of the difficulties in precisely fabricating the structures in optical wavelength. Here, we report the fabrication of large-area woodpile photonic crystal in GaAs at 1.55 μm wavelength by two-directional etching method without wafer bonding technique. A woodpile with 40×55×2.25 unit cells is fabricated in a two-patterning process, in which high-resolution electron beam lithography (EBL) defines 2D patterns, and then chemically assisted ion beam etching (CAIBE) provides high-aspect-ratio, anisotropic and deep GaAs etching at an angle of 45 degree relative to the wafer surface. The two-directional etching is a simple method to fabricate high-precision woodpile photonic crystals. The only alignment required in this process is performed by EBL overlay, which has a resolution of less than 30 nm. With our designs of ultra-high-Q nanocavities by unit cell size modulation, we can construct woodpile nanocavities with active materials, such as epitaxially-grown quantum well (QW) and quantum dot (QD) layers, using the same fabrication method without wafer bonding process.

Photonic crystals (PhC) are artificial structures fabricated with a periodicity in the dielectric function. This periodic electromagnetic potential results in creation of energy bandgaps where photon propagation is prohibited. PhC structures have promising use in thermal applications if optimized to operate at specific thermal emission spectrum. Here, novel utilization of optimized PhC's in thermal applications is presented. We demonstrate through numerical simulation the modification of the thermal emission spectrum by a metallic photonic crystal (PhC) to create high-efficiency multispectral thermal emitters. These emitters funnel radiation from a broad emission spectrum associated with a Plancklike distribution into a prescribed narrow emission band. A detailed quantitative evaluation of the spectral and power efficiencies of a PhC thermal emitter and its portability across infrared (IR) spectral bands are provided. We show an optimized tungsten PhC with a predominant narrow-band emission profile with an emitter efficiency that is more than double that of an ideal blackbody and ~65-75% more power-efficiency across the IR spectrum. We also report on using optimal three-dimensional Lincoln log photonic crystal (LL-PhC) emitters for thermophotovoltaic (TPV) generation as opposed to using a passive filtering approach to truncate the broadband thermal source emission to match the bandgap of a photovoltaic (PV) cell. The emitter performance is optimized for the 1-2μm PV band using different PhC materials, specifically copper, silver and gold. The use of the proposed PhC in TPV devices can produce significant energy savings not reported before. The optimal design of the PhC geometry is obtained by implementing a variety of optimization methods integrated with artificial intelligence (AI) algorithms.

By modifying the supporting structures of a conventional piezoelectric-on-substrate micromechanical (MM) resonator using phononic crystal (PC) slab structures with complete phononic band gaps (PBGs) the support loss in micromechanical resonators is suppressed and the quality factor of the fundamental extensional resonant mode is improved from approximately 1,200 to approximately 6,000. The conventional MM resonator and the PC resonators are both fabricated on the same chip and using the same fabrication process. The PC is made by etching a hexagonal (honeycomb) array of holes in a 15μm-thick slab of silicon. The radii of the holes are approximately 6.4μm and the spacing between the centers of the nearest holes is 15 μm. The conventional MM resonator is made of a rectangular structure with dimensions of 600 μm by 60 μm and the fundamental flexural and extensional modes of the structure in the smaller dimension are excited. In the third dimension, all the structures are made of a 15 μm silicon (Si) slab, a 100 nm layer of gold, a ~1 μm layer of zinc oxide, and a patterned 100 nm layer of aluminum electrodes stacked on top of each other to serve as the resonant mass and the transduction medium. The significant improvement obtained using the PC resonator structures makes them excellent candidates for next generation of MM resonators for wireless communication and sensing applications despite some minor remaining challenges.

In this paper we demonstrate the possibility of forming a new elastic filter structure based on the coupled resonator waveguides in phononic crystal slabs (CRAW) with superior performance over the conventional filters. The structures are made by etching a honeycomb array of holes in a free standing slab. This phononic slab structure exhibits an absolute phononic band gap for all polarizations of guided waves inside the slab including the Lamb and Love waves. We present an analysis of a different family of waveguides in phononic-crystal slabs, and illustrate the considerations that must be applied to achieve single-mode guided bands in these structures. Consequently, an unusual family of selective elastic filters composed of several single resonators that are coupled periodically through evanescent waves is obtained. The elastic energy is localized in the extended defect formed by the collective coupled resonators. The frequencies of the filters are sensitive to the geometrical parameters and to the separation distance between the indiviual resonators. Numerical simulations are performed using the finite element method and considering Zinc-Oxide slab.

Drawing on recent advances in understanding the origin of the photonic band gap observed in hollow core photonic crystal fibers, we apply the photonic tight binding model to a high air filling fraction fiber. By studying the interdependent effect of the apex, strut and air-hole resonators present in the photonic crystal cladding, we demonstrate that it is possible for a second photonic band gap windows to extend significantly below the air-line, whilst the general properties of the fundamental band gap remains relatively unaffected. We fabricate several hollow core fibers with extremely thin struts relative to the apex size. All fibers exhibit two strong transmission windows that bridge the benchmark laser wavelengths of 1064nm and 1550nm. These results pave the way to extend the guidance capability of low-loss hollow core fibers.

Optical coherence tomography is a technology which supplies the tomographic image using the optical interference. It uses the 1.31 μm wavelength for dental applications. Resolution problems of such a technology can be improved by using supercontinuum light sources as low coherent broadband light is achievable from optical supercontinuum. Photonic crystal fibers have the ability to generate the supercontinuum light even with moderate input power levels. Only thing to consider is to ensure zero or nearly zero dispersion of such fibers at the target 1.31μm wavelength. This paper presents design of a high nonlinear photonic crystal fiber with near-zero dispersion around 1.31μm wavelength based on the finite difference method. Robustness of the design is confirmed numerically by generating wideband supercontinuum.

In this paper we demonstrate the fabrication of long-period fiber gratings (LPFGs) based on the photonic crystal fibers (PCFs) with the UV gel infiltrated in all the air holes. The periodic index modulation of the fabricated LPFGs is induced by using the UV light through the amplitude masks with periods of Λ_G = 400 μm, 500 μm, and 600 μm, respectively. By measuring the output spectra of these fabricated LPFGs, we can observe clear notches in the transmission spectra. These notches correspond to the coupling from the core mode to the cladding modes. We also discuss the effect of exposure time of UV light on the grating properties of the fabricated LPFGs.

In this review, we discuss the progress and prospects offered by chalcogenide glass photonic crystals. We show that by making photonic crystals from a highly-nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the testing of two-dimensional Ge33As12Se55 chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to not only post-tune the devices properties but also create high Q cavities by using the material photosensitivity.

Glancing angle deposition (GLAD) facilitates the fabrication of nanostructured thin films with varying density, using a motion control algorithm governing substrate movements during film growth, which engineerings the film structure. Film architectures for specific optical applications including photonic crystals are easily produced with GLAD. A challenge in the photonic crystal field has been the realization of in-situ control of optical characteristics. We have demonstrated partial control of stopband optical characteristics using an electric field in a GLAD 1D photonic crystal by the electrophoretic movement of absorbing dye ions.

We present a novel method to fabricate photonic crystal for visible light control and demonstrate high resolution patterning of multiple structural colors using a single material. The material, termed as "M-Ink", whose color is magnetically tunable and lithographically fixable, is developed. By combining novel material system and specially designed instrument, we produce patterns with arbitrary spatial arrangements of colors with single material.

We identify factors affecting transmission and dispersive properties of photonic crystal waveguide (PCW) bends and show how they can be varied in a systematic manner to achieve wide bandwidth bends with high transmission and low dispersion. Our experiments show around 12 nm of bandwidth increase as compared to simple bends in a PCW at low group velocities. The bandwidth increase at high group velocities is more than 30 nm.

We present a design methodology for silicon-on-insulator photonic crystal waveguides to achieve wideband lowdispersion slow light with only tuning the position of the first three inner rows. We aim to maximize the group index - bandwidth product or the slowdown factor. Our design achieves a constant group index of 39.3 over 12 nm bandwidth around 1550 nm, corresponding to a slow down factor of 0.3.

An overmoded photonic crystal waveguide based on the three-dimensional woodpile lattice has been proposed for a highenergy charged particle accelerator. Critical to overall accelerator efficiency is the ability to couple power into an uninterrupted vacuum waveguide in a very small volume. We present designs and simulations of coupling to the waveguide, both from free space and from a waveguide adjoining it at 90 degrees. We discuss details of the computation, including the use of symmetries and extraction of the resulting transmission.

We present design, fabrication, and characterization results of a highly absorptive surface in the thermal infrared that draws on concepts from the frequency selective surface and metamaterials communities. At normal incidence this optically thin surface has an absorption of over 99%. Furthermore, it has a broad angular range (over 90% absorption at 60 degrees from normal). The simple structure is composed of a reflective metal layer, a roughly quarter-wave layer of lossy dielectric, and a top metal layer that is patterned with an array of subwavelength apertures. The design of the aperture allows spectral and angular control of the absorption/emission band. We will present simulation and measured results. Change in waveband and polarization could easily be changed from pixel to pixel in a focal plane array.

We present a semi-analytical Green's function-based technique for analyzing propagation loss in photonic crystal waveguides (PCWGs). The method only requires the complex band structure of the PCWG to calculate the transmission (or loss) of the structure. The plane-wave expansion method was used in this work to calculate the complex band behavior, and the power of this technique is demonstrated by comparing the results with the brute force simulation results for a PCWG. The possibility of extending this technique to the more practical arrangement of a random distribution of defects using a configurational average with coherent potential approximation theory will also be discussed.

The need for antennas with improved characteristics for communication and radar applications has resulted in an ever-increasing demand for research in the field of high impedance surfaces, which can work as an artificial magnetic conductor. One method in fabrication of these surfaces is formation of a metamaterial by patterning a metallic surface in the shape of space filling curves (e.g. Hilbert or Peanu Curves). In this paper, we present a novel semi-analytical solution to the problem of plasmonic propagation on these surfaces. The method is based on a previously presented Green's function formalism, which has been reported in an earlier paper of ours. We have modified and improved the method for analysis of periodic structures with a large number of spatial harmonics, and used different methods to get the necessary stabilization. Here propagating modes of different structures and their corresponding frequencies are calculated, and the possibility of frequency gap formation and stability of the method are investigated.

Computer calculation of photonic band structure for unit cells of various symmetry in the two-dimensional square lattice suggests that the bandgap calculated by traversing the ΓXM triangle in k-space is only reliable when the unit cell is C_4v symmetric. For structures of lower symmetry, examining a two-dimensional subset of the first Brillouin zone will give smaller bandgaps.

Ultracompact wave plate (UWP) will be one of the key elements in future all-optical photonic integrated circuits (PICs). In this paper, we propose UWPs based on periodic dielectric waveguides (PDWs) with air holes in conventional dielectric waveguides. The mode characteristics (for both TE and TM) and birefringence of PDWs are calculated by plane wave method (PWM). The transmission efficiencies and phase changing of TE and TM waves in PDW are obtained by finite-difference time-domain (FDTD) scheme. Based on the PDWs, the quarter-wave plates (QWPs) and half-wave plates (HWPs) are designed. Calculating results show that the proposed PDW has large birefringence (Δn>1) and can introduce 2π phase difference with a short length being less than λ. The size of low order UWPs are compact. The transmission efficiency of PDW is improved by taper structure. Based on the taper PDW, ultra-wide band (>100 nm) achromatic QWP is designed. Profiting from the waveguide guiding, the UWPs have low beam divergence and can be easily integrated with other photonic components. The UWPs have many potential applications in future PIC systems such as optical communications, optical measurements and sensors.

Simultaneous two-dimensional nanometric-scale position monitoring can be achieved in a simple interferometric setup by real-time probing a hexagonal photonic crystal glass substrate. The minimum detectable translational movement is determined by the period of photonic crystal array, and can be as high as 8 nm in the present work.

Close-packed 3D colloidal crystals, regular arrangement of mono-disperse silica or polymer spheres with diameter within the wavelength range of visible light, show many novel optical phenomena that are strongly dependent of the sphere-packing symmetry. From both analytical and experimental results, is well known that there are two predominant ways of stacking mono-disperse spheres to minimize the interstitial volume in a colloidal crystal. One of them leads to a close packed face-centered-cubic (fcc) structure, called synthetic opal, and, the other one, to an hexagonal close packed (hcp) structure. Although computer simulations show that the fcc structure is more stable, there are a lot of papers in which a hcp phase is observed. In this work, the photonic band structure of the fcc and hcp 200nm SiO₂ based colloidal crystals are calculated using the plane wave expansion method (PWEM). A comparative kinematic study of the refraction properties of the fcc and hcp structures is presented, showing that the effective refractive index depends basically of the dispersion relations and of the plane of polarization and that it is not limited by the refractive index of the composing materials.

In this paper we employ the full-vector finite-difference frequency-domain (FDFD) method to theoretically investigate the birefringent characteristics of three kinds of selectively liquid-filled photonic crystal fibers (PCFs). These birefringent PCFs are fabricated by asymmetrically infiltrating high-index liquids into the air holes of the PCFs. The birefringence values and the confinement losses of these birefringent selectively liquid-filled PCFs are compared and discussed. We also demonstrate the fabrication of the birefringent selectively liquid-filled PCFs, and the birefringence values can be successfully measured by using an optical fiber Sagnac interferometer.

We demonstrate the fabrication of the internally liquid-filled photonic crystal fibers (PCFs) with the liquids filled in inner air-hole layers of the PCFs. The outer air-hole layers are first blocked by using a selectively blocking technique with a polished fiber tip. The liquid is then infiltrated into the inner open holes through a vacuum injection method to obtain the internally liquid-filled PCFs. The measurement results show that the propagation losses of the internally liquid-filled PCFs can be efficiently reduced with the aid of the outer air-hole layers in the fiber cladding. By varying the operation temperature, we also demonstrate the thermally tunable optical properties of our fabricated internally liquidfilled PCFs.

Optical resonances in 1D photonic crystal microcavities are investigated numerically using finite-element light scattering and eigenmode solvers. The results are validated by comparison to experimental and theoretical findings from the literature. The influence of nanometer-scale geometry variations on the resonator performance is studied. Limiting factors to ultra-high Q-factor performance are identified.