This PDF file contains the front matter associated with SPIE Proceedings Volume 6480, including the Title Page, Copyright information, Table of Contents, Introduction (if any) and the Conference Committee listing.

We have obtained a dye-doped chiral photonic crystal (PC) film with reflection band gap much wider than its original band gap without dye dopants by using multiple-step fabrication processes. Moreover, the dye-doped chiral PC films using our multiple-step fabrication processes exhibit many oscillations within the broadened reflection band gap. The abrupt change of the optical density of state (DOS) around the oscillations provides the possibility of generating laser emission when the dye-doped chiral PC film is pumped by a pulsed laser with wavelength in the absorption region of the laser dye. Based on this property, we demonstrated random lasers which exhibit different multiple-mode laser wavelength at different spatial positions. Different from the random lasers induced by the scattering mechanism, the random lasers from the dye-doped cholesteric polymer film exhibit Gaussian-like beam shape and specific propagation orientation which is normal to the cholesteric planar surface. It is foreseeable that a high efficiency and high power broadband laser can be generated using cholesteric polymer films.

In a similar manner to the frequency selective surfaces commonly used in the microwave regime, we have designed antireflective surfaces in the mid-infrared (2-5 μm). Translation of microwave designs to the infrared is not trivial for several reasons. Properties of applicable IR materials are significantly different than their microwave counterparts. Additionally, the required feature sizes need a completely different fabrication methodology. Our surfaces are metallic, yet have a high-transmission angular and frequency passband. We take advantage of photon-plasmon interaction to maximize transmission through holes in the metal surface. Simulations have been completed using both rigorous coupled wave analysis and method of moments codes. The design process has followed a path that insures that we are able to fabricate the designed structures considering cases of normal and off-angle incidence. We designed our surfaces to be compatible with shapes that we will etch in silicon and then coat in gold: this process allows the greatest flexibility in etching shapes for vias while maintaining a metallic layer for plasmon propagation on the surface. We anticipate over 90% transmission in the infrared passband. Our design methodology would also be applicable to the 8-12 μm band.

We report that polaritonic thin films with a periodic array of subwavelength holes allow near-perfect transmission in the polariton gap where homogeneous films completely suppress transmission. We find that both propagating modes inside the subwavelength holes and surface resonances on the film interfaces play a crucial role in the transmission behavior. In the frequency range where both occur simultaneously, they interfere destructively and completely suppress transmission. When both mechanisms are spectrally separated, each individually results in enhanced transmission.

The sensitivity of an infrared gas sensor depends on the interaction length between radiation and gas, i.e. a reduction in cell size generally results in a reduced sensitivity, too. However, low group velocity regions in the bandstructure of photonic crystals should enable the realization of very compact gas sensors. Using photonic crystals based on macroporous silicon experimental results with CO₂ show an increase of the gas sensitivity in the photonic crystal compared to an empty cell of same dimensions. For practical applications the results are compared with gas measurements using conventional multireflection cells and hollow fiber setups.

We have been studying a novel 1D anisotropic photonic crystal structure which can be designed to have a strong resonant effect, a very low group velocity over a specific bandwidth. The structure requires two anisotropic layers and one isotropic layer per period and was first introduced by Figotin and Vitebskiy. By the careful design of the parameters of the structure, we can find a special band edge point which has fourth order degeneracy, and is called degenerate band edge (D.B.E). It was predicted that in the case of a transmission resonance in the vicinity of the D.B.E, the resonant field intensity increases as N⁴, where N is the total number of periods, while in the case of a regular band edge, the field intensity is proportional to N². By making a comparison among different anisotropic materials, we have found that the giant resonant effects in the vicinity of the D.B.E also need a large anisotropy of the materials. However, materials with the required anisotropy at optical wavelengths are difficult to find and so we use equivalent form-birefringence layer to replace the anisotropic layer in our photonic crystal structure design. In order to verify our design, we make a real device for use at microwave frequencies using a rapid-prototyping tool. Our measurement results show that using form-birefringence to design this novel device is feasible and can push this novel photonic crystal structure to a lot of potential applications.

In this paper, we present novel designs for all optical analog-to-digital converters simulated and realized in photonic crystal platforms. The designs presented were implemented on both photonic bandgap based structures as well as self collimation based structures. Numerical simulation results as well as fabrication results are also included. Characterization results validate the designs presented for a functional all optical two bit analog to digital converters in photonic crystals. The design presented can be further scaled to higher resolution conversion as well as to no optical frequencies if necessary.

Supercontinuum generation is often achieved using pulses from a femtosecond laser. Recent advances in highpower continuous-wave (CW) fiber lasers have made it possible to use these compact and rugged sources for supercontinuum generation. We briefly review the physical mechanisms behind supercontinuum generation and also treat some of the intricacies of numerically modelling a CW pump. This allows an investigation of, e.g., how the pump spectral linewidth affects the supercontinuum spectrum.

Hollow-core holey fibers are promising candidates for low-loss guidance of light in various applications, e.g., for the use in laser guide star adaptive optics systems in optical astronomy. We present an accurate and fast method for the computation of light modes in arbitrarily shaped waveguides. Maxwell's equations are discretized using vectorial finite elements (FEM). We discuss how we utilize concepts like adaptive grid refinement, higher-order finite elements, and transparent boundary conditions for the computation of leaky modes in photonic crystal fibers. Further, we investigate the convergence behavior of our methods. We employ our FEM solver to design hollow-core photonic crystal fibers (HCPCF) whose cores are formed from 19 omitted cladding unit cells. We optimize the fiber geometry for minimal attenuation using multidimensional optimization taking into account radiation loss (leaky modes).

Diamond-like silicon photonic crystals were fabricated by sequential chemical vapor deposition of silica and silicon on polymer templates photopatterned by holographic lithography. The optical properties of the 3D crystals after each processing step were measured and compared to the corresponding bandgap simulation. The core-shell morphology formed during CVD process is approximated using two level surfaces.

Recently, two-dimensional and three-dimensional periodic dielectric structures have been directly fabricated by laser holographic lithography to create novel geometric structures with high-precision tolerances. Multiple beam interference via beam splitting mirrors or diffractive optical elements produce iso-intensity contours that can be accurately recorded in photoresist and subsequently used as a template for creating photonic crystals with a complete or partial bandgap. We demonstrate single laser exposure method of forming three-dimensional photonic crystal templates in photoresist with multi-layer two-dimensional diffractive optical elements. Several photonic stopbands are identified in the near-infrared spectrum along multiple crystallographic directions.

Light emitted within a photonic crystal structure can be used to probe both the photonic density of states and the anisotropic propagation of light through the structure. Here we present results of angle- and polarization-resolved measurements of photoluminescence from three-dimensional ZnO photonic crystals. The ZnO inverse opals were fabricated by infiltration of polystyrene synthetic opal templates using atomic layer deposition. The resulting nanocrystalline ZnO structures exhibit strong UV emission as well as a broad defect emission peak, allowing us to observe the dispersion of the primary as well as higher-order PBGs over the entire visible spectrum. The spontaneous emission spectrum is strongly modified and anisotropic due to the effect of the photonic band structure. The observed features are correlated to transmission and reflection measurements as well as calculated (reduced) band structures in the Γ-L-K plane of the fcc Brillouin zone. Apart from the suppression and redistribution of light near the primary and higher band gaps, we observe a strong enhancement in the PL peaks due to light propagation in higher (e.g. 5th and 6th)photonic bands at frequencies and angles where no PBG exists.

Porous silicon (PSi) is an attractive material for fabrication of multilayer optical devices such as Bragg reflectors, Fabry-Perot resonators and other novel (optical) components. Such devices are characterized by a periodic modulation of the refractive indices in alternating layers and can be classified as 1D photonic crystals. 2D photonic bandgap structures can be also obtained using a variation of applied potential on the back side of the sample during electrochemical formation of the multilayers. This technique allows a fabrication of spatially distributed filters on the millimeter size scale. In this paper, a new method is presented which uses a front side protective mask for the creation of 2D photonic bandgap structures on the micron scale. The devices obtained by this technique can be used for the creation of spatially distributed filters. The front side protective mask controls lateral undercut in multiple ways depending on the mask material. By varying the design and material of the protective mask, PSi interference filters with desired optical parameters across a field of view can be realized. In this paper, a novel, simple method to produce 2D periodic multilayer structures is described. In particular, the focus is on the changes in the photonic crystal cavities when various mask materials are used. In addition, a new type of active optical components for a chip-to chip interconnection based on the combination of our method and MEMS technology is presented.

The phenomenon of slow light in photonic crystal waveguides is discussed. Rather than maximising the slowdown factor, we believe that slow light is only useful for all-optical data processing if there is sufficient bandwidth, hence a slowdown factor of order 10-100 is more favourable, given that it enables bandwidths of order 1 THz or more to be realised. As a specific example, we demonstrate a slowdown factor of 12 (group index of 25) over a bandwidth of 2.5 THz in a W2 photonic crystal waveguide. Furthermore, slow light can only be useful if it is not compromised by losses. Due to recent improvements in our technology, we can now achieve losses of order 4 dB/cm, which is amongst the best reported for W1 photonic crystal waveguides.

We compare the intrinsic radiation loss of a coupled-resonator optical waveguide in a photonic-crystal slab to that of a single, isolated resonator. We find that due to interference between different resonators, the waveguide can have far lower loss than the isolated cavity; in other cases it can have far greater loss.

Silicon nanophotonics has recently attracted great attention since it offers an opportunity for low cost opto-electronic solutions based on silicon complementary metal oxide semiconductor (MOS) technology. Photonic crystal (PhC) structures with slow photon effect are expected to play a key role in future large-scale ultra-compact photonic integrated circuits. A novel vertical-MOS-capacitor-based silicon PhC waveguide structure was proposed to achieve active transmission control via the free carrier plasma dispersion effect. We designed and fabricated a single-arm PhC waveguide with MOS gate defect using silicon-on-insulator (SOI) substrate and demonstrated that a defect mode was present in the infrared region. Plane wave expansion (PWE) method based simulation indicated that high group index of the fabricated PhC waveguide could be achieved near the transmission band edge. Further investigation demonstrated that such PhC MOS capacitor would be a good candidate to realize ultra-compact transmission control.

We present a method for systematic design of Photonic Crystal Waveguide (PCW) bends to achieve high transmission and low dispersion over large bandwidths by identifying factors and studying their effects on transmission and dispersive properties of bends.

We show that femtosecond optical pulses at optical communication wavelengths can be used for real time dispersion measurement of photonic crystal waveguides. Spectral resolutions on the order of one nanometer and bandwidths as large as tens of nanometers are demonstrated in real time measurements. Preliminary results are shown and discussed.

We have performed a numerical solution for band structure of an Abrikosov vortex lattice in type-II superconductors forming a periodic array in two dimensions for applications of incorporating the photonic crystals concept into superconducting materials with possibilities for optical electronics. The implemented numerical method is based on the extensive numerical solution of the Ginzburg-Landau equation for calculating the parameters of the two-fluid model and obtaining the band structure from the permittivity, which depends on the above parameters and the frequency. This is while the characteristics of such crystals highly vary with an externally applied static normal magnetic field, leading to nonlinear behavior of the band structure, which also has nonlinear dependence on the temperature. The similar analysis for every arbitrary lattice structure is also possible to be developed by this approach as presented in this work. We also present some examples and discuss the results.

Compact on-chip wavelength demultiplexers and spectrometers are essential components for a variety of applications including integrated optical information processing devices, optical communications, and integrated optical sensing. Implementation of such devices requires strong dispersion in the optical materials, which can be realized using unique dispersive properties of photonic crystals (PCs). Possibility of integration, compactness, and compatibility with different host materials are the main advantages of PC based demultiplexers and spectrometers compared to other techniques. Here, we show an implementation of superprism-based photonic crystal devices (using a diffraction compensation scheme) that improves the performance of these devices compared to the conventional implementation. Structures obtained through optimization have been fabricated in SOI wafers using e-beam writing and ICP etching, and spatial separation of channels (with good isolation) in these superprism devices is experimentally demonstrated. The performance of these superprism devices as general-purpose spectrometers and for locating spectral features in a sensing platform will be also demonstrated and discussed. Further steps for improvement of these devices are considered and the related implementation issues are investigated.

Photonic crystal based superprism offers a new way to design new optical components for beam steering and DWDM application. 3D photonic crystals are especially attractive as they could offer more control of the light beam based on the needs. A polygonal prism based holographic fabrication method has been demonstrated for a three-dimensional face-centered-cubic (FCC)-type submicron polymer photonic crystal using SU8 as the photo-sensitive material. Therefore antivibration equipment and complicated optical alignment system are not needed and the requirement for the coherence of the laser source is relaxed compared with the traditional holographic setup. By changing the top-cut prism structure, the polarization of the laser beam, the exposure and development conditions we can achieve different kinds of triclinic or orthorhombic photonic crystals on demand. Special fabrication treatments have been introduced to ensure the survivability of the fabricated large area (cm²) nano-structures. Scanning electron microscopy and diffraction results proved the good uniformity of the fabricated structures. With the proper design of the refraction prism we have achieved a partial bandgap for S+C band (1460-1565nm) in the [111] direction. The transmission and reflection spectra obtained by Fourier transform infrared spectroscopy (FTIR) are in good agreement with simulated band structure. The superprism effects around 1550nm wavelength for the fabricated 3D polymer photonic crystal have been theoretically calculated and such effects can be used for beam steering purpose.

Diffraction properties of a two-dimensional photonic crystal is presented. Diffraction experiments are carried out using a ring beam and the relevant experimental designs are shown. Drastic ring deformations are observed after diffractions, for different kind of ring beams. The diffraction properties are analyzed using the equ-frequency surface and the photonic band structure of a photonic crystal. The paper also describes the fundamental difference between the diffraction properties of photonic crystals with weak and finite modulation in their dielectric property.

A method of inverse design is applied to generate a new family of optical devices named scattering optical elemetns (SOE). The two dimensional (2D) designs consist of a few layers of 0.4&mgr;m x 0.4&mgr;m square-shaped bars etched in gallium arsenide. SOEs are defined as a class of computer-generated optical devices whose functionalities are based on the multiple scattering by their individual constituents. For realization of the aforementioned devices, two-dimensional photonic plates could be fabricated by only a single integrated circuit processing procedure followed by micromanipulation assembling. A small library of compact SOE devices are presented: A focusing device, a wavelength de-multiplexer, an optimized optical source, an optical MEMS switch and a cloaking device.

We present an efficient model for the simulation of spatially incoherent sources based on Wiener chaos expansion (WCE) method with two orders of magnitude shorter simulation time over the brute-force model. In this model the stochastic wave propagation equation is reduced to a set of deterministic partial differential equations (PDEs) for the expansion coefficients. We further numerically solve these deterministic PDEs by finite difference time domain (FDTD) technique. While the WCE method is general, we apply it to the analysis of photonic crystal spectrometers for diffuse source spectroscopy.

We calculate linear and nonlinear optical effective refractive indices of finite period one-dimensional photonic crystals, Bragg reflectors and photonic crystal microcavities, by using numerical dispersion relation. We discuss optical dispersive properties of both the Bragg reflectors and the photonic crystal microcavities. For Bragg reflectors, optical Kerr nonlinearity is enhanced at bandgap edges, and the singularity problem at bandgap edges, occurred in Bloch index for infinite structure, is removed by the numerical dispersion relation. Also, the numerical dispersion relation is adopted to describe optical property of photonic crystal microcavities, for which Bloch index is not available. Optical Kerr nonlinearity in photonic crystal microcavities is found to be more enhanced at optical defect modes than at bandgap edges. Z-scan profiles of a Bragg reflector and a photonic crystal microcavity are numerically simulated based on the calculated nonlinear effective refractive indices, which show peaks at bandgap edges and defect mode incurred by dispersion anomaly.

Photonic crystal membrane microcavities lend themselves to applications like novel highly efficient emitters of incoherent light and sensing devices, and support fundamental investigations on material properties. On the one hand these applications demand a high quality factor at a tailored resonance frequency of the cavity. On the other hand it is important to provide an efficient coupling of the emission to an optical system or waveguide. Based on these requirements photonic crystal microcavities are designed and optimized with a novel 3D Finite Element (FE) Maxwell solver which is capable of solving eigenproblems as well as source problems. The solver features the computation of the farfield to support the investigation of the spatial emission pattern and is applicable to arbitrary 3-dimensional microcavities. Different photonic crystal configurations have been investigated with respect to their coupling efficiency and optimization strategies are proposed.

In this paper, we present the simulation results on the absorption modification in a two-dimensional photonic crystal slab (2D PCS) structure, based on three-dimensional finite-difference time-domain technique (3D FDTD). Significantly enhanced absorption at defect level was obtained at surface normal direction in a single defect photonic crystal cavity, for both in-plane and vertical sources. An absorption enhancement factor in the range of 100-6,000 was obtained under different operation conditions, based on the normalized absorption power spectral density with respect to the reference slab without photonic crystals. Complete absorption suppression within the photonic bandgap region was also observed in defect-free cavities. High spectral selectivity and tunability was feasible with defect mode engineering.

Using polynomial expansion of electromagnetic fields has been already reported for extraction of E polarized defect modes in two-dimensional photonic crystals. This approach is now applied to straight single-line defect optical waveguides, where H polarized defect modes are analytically extracted for the first time. Electromagnetic fields are expanded in accordance with the Floquet theorem, where each Floquet order is itself expanded in terms of Hermite polynomials and finally a new set of linear ordinary differential equations with non-constant coefficients is obtained. This set of equations is handled by employing differential transfer matrix method. In this fashion, algebraic and easy to solve dispersion equations are derived, where each mode is effectively sought out in the Hilbert space spanned by Hermite polynomials. Effective index theory based on static field approximation is also presented to show the strong similarity between eigenmodes of photonic bandgap waveguides and those of slab waveguides with uniaxial anisotropic claddings.

A new formalism for calculating the photonic band structure of multi-layer photonic band gap (PBG) materials is presented. The formalism expresses all boundary conditions in terms of tangents rather than exponential functions. The formalism is compact, algorithmically simple, and physically appealing, and provides a new conceptual framework for describing the photonic band structure of layered materials. Its simplicity makes it possible to represent eigenfrequency conditions using geometric constructs, find a factored form of the secular equation, and derive analytic eigenfrequency conditions and analytic wave functions for multi-layer structures. Computationally, the new formalism makes it possible to find explicitly the complete band structure of multi-layer PBG materials with integer ratios of optical path lengths (i.e., any combination of quarter-wave, half-wave, etc., stacks) through a single diagonalization of a low order secular equation, the alternative being an implicit root search via the transfer matrix formalism. The formalism is demonstrated on multi-layered structures arranged in the Fibonacci sequence and a half-wave-quarterwave- eighth-wave PBG.

We present two-dimensional photonic-crystal waveguides for fluid-sensing applications in the sub-terahertz range. The structures are produced using a standard machining processes and are characterized in the frequency range from 67 to 110 GHz using a vector network analyzer. The photonic crystal consists of an air-hole array drilled into a high-density polyethylene block. A waveguide is introduced by reducing the diameter of the holes in one row. The holes can be loaded with liquid samples. For all structures we observe photonic band gaps between 97 and 109 GHz. While the pure photonic crystal shows the deepest stop band (28 dB), its depth is reduced by 5 dB when inserting a waveguiding structure. The depth of the photonic band gap is further reduced by several decibels depending on the refractive index of the liquid that is inserted. With this type of fluid sensor we can clearly distinguish between cyclohexane and tetrachloromethane with refractive indices of 1.42 and 1.51, respectively. The results are in good agreement with theoretical calculations based on the 2D finite-difference time-domain (FDTD) method.

Photonic crystals (PCs) have been one of the new, exhilarating topics in the last decade. The intent of this paper is to provide an understanding of two dimensional PC waveguides and the guiding mechanism associated with the structures. The basic understanding of two dimensional waveguides can be applied to more complex structures such as those found in three dimensional PCs. Results presented consist of different two dimensional waveguide cases, for both the line defect and the coupled cavity variety. It has been shown that PCs do not rely on index guiding, as conventional optical waveguides do, but that they do rely on distributed Bragg reflection. It has also been shown that in the case of defects, such as a waveguide, the size of the photonic bandgap is not the main determinant of wave confinement in that waveguide. The group index is a good measure of the degree of reflection one expects to see along the propagation direction of a waveguide.