For photonic devices, extending beyond the planar regime to the third dimension can allow a higher degree of integration and novel functionalities for applications such as photonic crystals and integrated optical circuits. Although conventional photolithography can achieve both high quality and structural control, it is still costly and slow for three-dimensional (3D) fabrication. Moreover, as diverse functional polymers emerge, there is potential to develop new techniques for quick and economical fabrication of 3D structures. We present a 3D microfabrication technique based on the soft lithographic technique, called two-polymer microtransfer molding (2P-μTM) to accomplish low cost, high structural fidelity and tailorable 3D microfabrication for polymers. Using 2P-μTM, highly layered polymeric microstructures are achievable by stacking planar structures layer by layer. For increased processing control, the surface chemistry of the polymers is characterized as a function of changing ultraviolet dosage to optimize yield in layer transfer. We discuss the application of the 2P-μTM to build polymer templates for woodpile photonic crystals, and demonstrate methods for converting the polymer templates to dielectric and metallic photonic crystal structures. Finally, we will show that 2P-μTM is promising for fabricating 3D polymeric optical waveguides.

To assist the growth of the telecommunication sector, new types of optical components such as those based on optical interference filter technology are critical. Existing technologies based on thin-film processing for production of optical communications filters have rapidly advanced. Although the Fabry-Perot bandpass filters made by deposition of alternate layers with high- and low- refractive index have a broad rejection band and a narrow passband, this technique does not allow for the control of filter parameters such as specification and adjustment of the transmitted wavelength at any place across the surface of the filter. The new approach discussed in the paper is directed toward the anodization of silicon to fabricate not only multilayer optical filters with a uniform passband across the field of view but also specially designed passbands at any single point in the field of view of the optical system. In particular, the realization and characterization of spatially distributed filters made of porous silicon are presented. These filters are able to select various passbands in the visible and IR regions. The filters were fabricated on p⁺ and p - type doped substrates. By varying the electrode configuration on the backside of wafer and the applied potential during electrochemical etching, the desired spatially distributed filter can be formed. The impact of wafer resistivity on filter parameters is discussed.

Three-dimensional periodic dielectric structure can be described by band theory, analogous to electron waves in a crystal. Photonic band gap (PBG) structures were introduced in 1987. The PBG is an energy band in which optical modes, spontaneous emission, and zero-point fluctuations are all absent. It was first theoretically predicted that a three-dimensional photonic crystal could have a complete band gap. E. Yablonovitch built the first three-dimensional photonic crystal (Yablonovite) on microwave length scale, with a complete PBG. In nature, photonic crystals occur as semiprecious opal and the microscopic structures on the wings of some tropical butterflies, which are repeating structures (PBG structure/materials) that inhibit the propagation of some frequencies of light. Pacific Northwest National Laboratory (PNNL) has been developing tunable (between 3.5 and 16 μm) quantum cascade lasers (QCL), chalcogenides, and all other components for an integrated approach to chemical sensing. We have made significant progress in modeling and fabrication of infrared photonic band gap (PBG) materials and structures. We modeled several 2-D designs and defect configurations. Transmission spectra were computed by the Finite Difference Time Domain Method (with FullWAVE_TM). The band gaps were computed by the Plane Wave Expansion Method (with BandSOLVE^TM). The modeled designs and defects were compared and the best design was identified. On the experimental front, chalcogenide glasses were used as the starting materials. As₂S₃, a common chalcogenide, is an important infrared (IR) transparent material with a variety of potential applications such as IR sensors, waveguides, and photonic crystals. Wet-chemical lithography has been extended to PBG fabrication and challenges identified. An overview of results and challenges will be presented.

We show that two-dimensional photonic crystals can be designed to have dispersion relations with an extended ultra-flat cross-section, meaning that for a fixed wave vector component k_x the frequency of a band is almost constant when the other wave vector component, k_y, takes all possible values. These ultra-flat bands are the result of a non-trivial saddle point in the dispersion relation located in the interior of the Brillouin zone. Interesting consequences include 1D-like behavior, improved super-collimation, and enhanced density of states.

One of the most surprising things about photonic crystals is not the existence of the band gap, but the fact that a large, ordered array of scatters can be transparent to light within certain spectral regions. We have identified a new, general effect in which the band gap of a photonic lattice can be suppressed by unexpected mode degeneracy, rendering a photonic crystal completely transparent to all frequencies across two or more distinct bands.

The feasibility of an electrically programmable photonic crystal (PC) is investigated theoretically based on the metal-insulator transition of vanadium dioxide (VO₂). We propose a slab structure based on VO₂ whose dielectric properties can be modulated by selectively applying the bias on a lithographically defined array of gate electrodes to induce the phase transition. So, unlike the ordinary PCs, wave propagation in the desired structure may be switched on/off or redirected to our satisfaction. To examine the idea, the photonic band structure (PBS) and the wave guiding characteristics are investigated by using the iterative plane wave expansion and the finite difference time domain methods. The results clearly indicate that the changes induced in the VO₂ dielectric properties via the phase transition can enable effective modulation of wave propagation at a high speed, offering a promising opportunity for a photonic circuit that can be programmed or reconfigured on demand.

A detailed study was carried out to understand the photonic crystal design rules with very high dielectric constant (ε>13), based on plane wave expansion and finite difference time-domain (FDTD) techniques. It is found that the optimal dielectric constant contrast is indeed the one between conventional semiconductors (ε=12-14) and air. Either too high or too low contrast can lead to the reduction of complete photonic bandgap. With very high bulk dielectric constant (ε=20-25), PbSe nanocrystal quantum dots (NQDs) are suitable for air hole based PC structure with large TE gap. On the other hand, NQD backfilled photonic crystals with tunable bandgap is proposed based on the control of packing density of NQDs inside the air holes of photonic crystal structures. Both theoretical and experimental results on the integration process are reported.

We present photonic crystal structures that exhibit small group velocity of light, which can be used as compact optical delay component. We experimentally measure the group velocity reduction to be less than 0.008c. By breaking the rotation symmetry of the structure we also use them to control the polarization of light. Finally, we demonstrate a new type of laser by fabricating array of coupled photonic crystal nanocavities in active medium, which improves differential quantum efficiency and laser output power. In our experiment, we observe a single mode lasing and measure the output powers that are two orders of magnitude higher than in single nanocavity lasers.

We propose a systematic approach to miniaturize magneto-optical device down to a single wavelength scale through the use of photonic crystal resonances. The nonreciprocal transport, typically found in magneto-optics, is highly enhanced in structures with strong field localization. The devices are magnetically biased along the out-of-plane direction (Voigt configuration). An optimized magnetic domain design maximally couples the standing-wave eigenstates in the resonance. As a conceptual demonstration, we demonstrate the design guideline in two-dimensional photonic crystal cavities, which can be readily extended into designing two-dimensional slab structures with the same functionality. A three-port junction circulator containing bismuth-iron-garnet is modeled with finite-difference time-domain schemes and demonstrates a 30dB-isolation bandwidth well over 100GHz.

The key feature that gives photonic crystals (PhCs) their ability to form a photonic band structure (PBS) is their translational symmetry. Structures that do not have translational symmetries also have a PBS. One explanation as to how these structures generate a PBS involves long-range interactions resulting in fractal dispersion relations (e.g. 1-D quasi-crystals, Fibonacci layers, etc.) However, long-range interactions do not fully explain why 2-D quasi-crystals structures also exhibit a PBS. This paper proposes an explanation for such results: by applying rotation operators from the SO(2) group to 1-D quasi-crystal dispersion relations. This process mimics the way electronic state amplitudes are calculated when such states have an angular dependence. Simulations results are presented in this paper.

Coupled optical cavities are constantly attracting increased attention in telecommunication applications. For an infinite chain of optical cavities, also known as the coupled resonator optical waveguide (CROW), the tight binding approximation has been used in order to evaluate its dispersion characteristics and the modal fields. In this paper, the accuracy of the tight binding formalism is investigated for a finite chain of optical cavities of arbitrary length. This approximation allows the derivation of simple analytical formulas for the resonant frequencies and the corresponding modal fields, which involve only the resonant frequency of the isolated cavity and the coupling coefficients between two consecutive coupled cavities. The equations for the modal fields involve an expansion in terms of displaced versions of the field distribution of the mode of the isolated cavity and simple trigonometric functions. These analytical results are compared with the numerical results of the plane wave expansion method in the case of a finite photonic crystal chain of coupled resonators and an excellent agreement is observed even if the cavities are placed close together. The results clearly indicate the usefulness and accuracy of the tight binding formalism for the description of coupled optical resonators.

Large and controllable polarization splitting effects are demonstrated based on liquid crystal infiltrated two-dimensional photonic crystals with silicon as a background material. Due to the strong birefringence of the liquid crystal, the dispersion curves of the two polarizations are distinctly different, resulting in large splitting between the two polarizations. Extremely large splitting, as large as 90 degree, can be obtained. Moreover, the splitting can be substantially tuned upon re-orienting the optic axis of liquid crystal. The influence of incident angle and the birefringence of the LC to the polarization splitting are also analyzed.

The good optical transmission of hollow-core photonic crystal fiber and their relative low insertion loss in conventional fiber network gave rise to a new type of all-fiber gas-phase devices. These range from Raman converters as laser sources, compact frequency standard devices for laser frequency control to electromagnetically-induced transparency and saturable absorption for quantum optical devices. Here I report on the performance of these devices and their prospects.

Microstructured optical fibers as new optical objects have been developed in the recent past years, firstly from silica glass and then from other oxide glasses such as tellurite or different heavy cations oxide glasses. However very few results have been reported concerning non-oxide glasses and more particularly chalcogenide glasses. In a photonic crystal fiber the arrangement of air holes along the transverse section of the fiber around a solid glassy core leads to unique optical properties, such as for example broadband single-mode guidance, adjustable dispersion, nonlinear properties. Since the effective modal area is adjustable thanks to geometrical parameters, chalcogenide microstructured fibers with small mode area are of interest for nonlinear components because of the intrinsic non linearity of chalcogenide glasses, several order of magnitude above these of the reference silica glass (100 to 1000 times the non linearity of silica glass). On the other hand, chalcogenide holey fibers with large mode area are of interest for infrared power transmission, in a wavelength range out of reach of silica fibers, and more particularly in the 3-5 μm atmospheric window. The aim of this paper is to present more specifically the recent results that have been achieved in the elaboration, light guidance and characterization of photonic crystal fibers from the sulfide Ge₂₀Ga₅Sb₁₀S₆₅ glass, which presents a large transparency window from 600 nm to 11 μm.

Modal solutions for photonic crystal fibers (PCFs) with circular air holes in a hexagonal matrix are presented, using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, modal hybridness, modal birefringence and group velocity dispersion values have been determined for a representative range of PCFs and the results obtained are shown and conclusions drawn. The effect of the structural asymmetry and modal confinement on the optimization of the modal birefringence is also thoroughly studied and presented here. The effect of total power on the effective indices and spot-sizes of nonlinear PCFs is also presented.

Waveguides in photonic crystals are one-dimensional photonic systems, with a richer basic physics than micro/nanocavities thanks to their extended nature. We evidence various roles of the one-dimensional singularities that occur at zero-group velocity points dispersion relations and mode anticrossings: One role is the demultiplexing in a space-localized fashion, combining properties of the Fabry-Perot and grating dispersive devices in a miniature footprint. Various aspects of the realization of such devices will be presented, towards WDM or coarse WDM applications in the framework of the european FUNFOX project. Another role is the possiblity to enhance gain in inverse proportion of the slwoed-down group velocity. A third possiblity is to produce a Purcell effect and thus a shorter lifetime for emitters embedded in such waveguides. This last possibility raises the prospect of an integrated high efficiency source with controlled photon modes.

We show that simultaneous perturbation of periodicity and radius of air holes next to the guiding region in a photonic crystal waveguide results in low loss and large bandwidth waveguides that are also single mode. We also show the results of a single shot spectral phase measurement that can be used for real time dispersion measurement of photonic crystal waveguides.

We study tunable time-delay devices in which the time delay is tuned by changing the group velocity of the propagating signal. The device is designed to place the operating frequency near a photonic band edge. This enhances the change in delay for a given tuning range of the device refractive index. Here we provide an extended explanation of mode symmetry, nomenclature, and the complete band structure of a sample, integrated device to aid the understanding of our previously published work.

We report the design, fabrication and optical characterization of total internal reflection segmented-cladding fibers for the middle-infrared spectral range 2-20 μm. Segmented cladding is a novel fiber design in which the uniform core of high refractive material is surrounded by a cladding of alternating segments of high and low refractive indices. Segmented cladding fibers are capable of maintaining a single-mode operation over a wide spectral range with a large core area. The design of the fibers and the simulations were made using the radial effective index method. The fibers were extruded from silver-halide crystals by using the 'rod in tube' method. Using this method we were able to construct large core fibers which exhibited few-modes and relatively low losses at 10.6 μm.

We experimentally demonstrate subwavelength resolution imaging at microwave frequencies by a three-dimensional (3D) photonic crystal flat lens using full 3D negative refraction. The flat lens is made of a body-centered cubic photonic crystal (PhC) whose dispersion at the third band results in group velocity opposite to phase velocity for electromagnetic waves. The photonic crystal was fabricated in a layer-by-layer process. Two different sources (monopole and pinhole) were used as imaged objects and a monopole detector was employed for detection in the image region. By scanning the detector, we obtained the images of the pinhole and monopole sources, seperately. The image of the pinhole sources had subwavelength feature size in all three dimensions, which predicts a 3D imaging capability of the flat lenses. An image of two pinhole sources with subwavelength spacing showed two resolved spots, which further verified subwavelength resolution.

Wavelength demultiplexing is one of the major applications of unique dispersion properties of photonic crystals (PCs). Possibility of integration and compactness are two main advantages of PC based demultiplexers compared to other demultiplexing techniques for applications including compact spectrometers (for sensory applications) and WDM demultiplexers. Here, we show that resolution and size limitations of conventional superprism-based photonic crystal demultiplexers are caused by the choice of configuration. We suggest an alternative implementation (combining superprism effect and focusing) that improves the performance compared to the conventional implementation in terms of being more compact and relaxing the requirement for divergence angle of the incident beam. We use effective index model to describe the beam behavior inside the photonic crystal region. Using this model, effective indices (second order and third order) are calculated directly from the band structure and are used to find the optimal operation parameters for the demultiplexing device. Detailed calculations show that the required size of preconditioned superprism photonic crystal demultiplexers scales up as N^5/2 (N being the number of channels which is proportional to the resolution of the device) which shows significant advantage over N⁴ dependence in conventional superprism-based devices, especially for high resolutions required in practical DWDM systems or spectroscopic applications. 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 focusing superprism devices is experimentally demonstrated.

We present a technique for manipulating the dispersive properties of low index periodic structures using microfluidic materials that fill the lattice with various fluids of different refractive indices. In order to quantify the modulation of the optical properties of the periodic structure we use Equifrequency contours (EFC) data to calculate the frequency dependant refractive index and the refractive angle. We further introduce various types of defects by selectively filling specific lattice sites and measuring the relative change in the index of refraction. Finally we design and optically characterize an adaptive low index photonic crystal based lens with tunable optical properties using various microfluidics. We also present experimental results for a silicon based PhC lens used an optical coupling element.

Combining organic films with high Kerr-nonlinearities and highly optimized photonic nanostructures could lead to new fast switching elements. Fabry-Perot cavities are fabricated by incorporating an organic material between two dielectric mirrors. Using femto-second pump and probe measurements we characterize these hybrid 1-D photonic band gap structures for various organic materials. By varying the pump beam wavelength across the cavity resonance we are able to delineate between the various underlying nonlinear processes. Comparing these measurements with computations we are able to quantify both the refractive and absorptive nonlinear coefficients of various organic materials.

An ultra-compact silicon electro-optic modulator was experimentally demonstrated based on highly dispersive silicon photonic crystal (PhC) waveguides. Modulation operation was demonstrated by carrier injection into an 80 μm-long silicon PhC waveguide of a Mach-Zehnder interferometer (MZI) structure. The π phase shift driving current, I_π, across the active region is as low as 0.15 mA, which is equivalent to a V_π of 7.5 mV when a 50 Ω impedance-matched structure is applied. The modulation depth is 92%. Highly dispersive PhC fibers were previously proposed to reduce the payload of true-time delay (TTD) modules for phased-array antenna (PAA) systems. The payload reduction factor is proportional to the enhanced dispersion of highly dispersive PhC fibers. An ultra-large dispersion of -1.1×10⁴ ps/nm•km with the full width at half maximum (FWHM) of 40 nm was numerically simulated from a dual core PhC fibers. The payload reduction factor of the TTD module is as high as 110 compared to that using conventional dispersion compensation fibers (D = -100 ps/nm•km).

We present a theoretical condition for achieving three-dimensional self-collimation of light in a photonic crystal. Such effects provide a very interesting mechanism for developing integrated circuits in 3D crystals that can be synthesized in a large scale. We also show that in a dielectric waveguide with a photonic crystal core, the modal properties are very unusual. In particular, a single-mode waveguide for the fundamental mode with a large core and a strong confinement can be realized. This is potentially important for suppressing modal competition in laser structures.

We demonstrate the coupling of PbS quantum dot emission to photonic crystal cavities at room temperature. The cavities are defined in 33% Al, AlGaAs membranes on top of oxidized AlAs. Quantum dots were dissolved in Poly-methyl-methacrylate (PMMA) and spun on top of the cavities. Quantum dot emission is shown to map out the structure resonances, and may prove to be viable sources for room temperature cavity coupled single photon generation for quantum information processing applications. These results also indicate that such commercially available quantum dots can be used for passive structure characterization. The deposition technique is versatile and allows layers with different dot densities and emission wavelengths to be re-deposited on the same chip.

Polarization-resolved second-harmonic spectra are obtained from the resonant modes of a two-dimensional planar photonic crystal microcavity patterned in a free-standing InP slab. The photonic crystal microcavity is comprised of a single missing-hole defect in a hexagonal photonic crystal host formed with elliptically-shaped holes. The cavity supports two orthogonally-polarized resonant modes split by 60 cm^-1. Sum-frequency data are reported from the nonlinear interaction of the two coherently excited modes, and the polarization dependence is explained in terms of the nonlinear susceptibility tensor of the host InP.

We propose and demonstrate a new labyrinth based metamaterial structure that solves two major problems related to the split-ring resonator based structures. One of the problems related to the split-ring resonator structure is the bianisotropy, and the other problem is the electric coupling to the magnetic resonance of the split-ring resonator structure. These two problems introduce difficulties in obtaining isotropic left-handed metamaterial mediums. The new structure that we propose here solves both of these problems. We further show that in addition to the magnetic resonance, when combined with a suitable wire medium, the structure that we propose exhibits left-handed transmission band. A two-dimensional metamaterial based on the labyrinth structure is used to study imaging of a point source. Our experimental results show that it is possible to image the point source with half widths as small as λ/4 by using the labyrinth based metamaterial.

Arrays of lead lanthanum zirconate titanate disks are fabricated on Pt electrodes by wet etching of thin films processed from sol-gel precursors, which may be applicable as defect cavities with electrically tunable resonance wavelength when embedded inside 2-D Si photonic crystals. Using e-beam lithography followed by sputtering and liftoff, Pt etch masks with diameters down to 1μm are deposited on pyrolyzed PLZT films. Wet etching using diluted hydrochloric acid generates discrete PLZT disks with integrated top and bottom Pt electrodes. The dimensions of the PLZT disks are determined by the diameter of the Pt etch mask, although undercutting becomes a significant issue as etch mask size decreased. The effects of varying PLZT pyrolysis temperature on the etching rate and film quality after sintering are examined. Dielectric testing of wet etched PLZT film after sintering showed that the devices have short circuited, suggesting that the deformation of the top Pt electrode over the undercut PLZT during sintering may significantly hinder the applicability of the current wet etching technique. Alternate methods for the patterning of PLZT for integration into photonic crystals are proposed.

Si nanophotonics is anticipated to play a critical role in the future ultra-compact system integration due to the maturity of sub-micron silicon complementary metal oxide semiconductor (CMOS) technology. Photonic crystals (PhCs) provide a promising platform for developing novel optoelectronic devices with significantly reduced device size and power consumption. The active control of photonic crystal waveguides (PCWs) incorporated in Mach-Zehnder interferometers has been investigated in this paper. We designed and fabricated a PCW based silicon thermo-optic (TO) switch operating at 1.55 μm. A novel device structure was proposed to enhance the heat exchange efficiency between the source and the active PCW region, which resulted in a faster switching time (< 20μs) compared with the conventional structure. The required π phase shift between the two arms of the MZI has been successfully achieved within an 80 μm interaction distance. The maximum modulation depth of 84% was demonstrated for switching power of 78mW. For high-speed applications, a p-i-n structure based PCW electro-optical (EO) MZI modulator was proposed. The transient performance of such a device was evaluated using a two-dimensional semiconductor device simulator MEDICI. The simulated structure demonstrated a great potential to realize high-speed ultra-compact Si modulators in the GHz region.

We report simulations showing tunable terahertz oscillations of the electromagnetic field provided by the Bloch oscillations of a short photonic wave packet in a tilted band structure. The structure consists in a finite one-dimensional photonic crystal inhomogeneously chirped by a slowly-varying refractive index gradient. Tunability is obtained by relocating the Bloch oscillations center in regions characterized by different local band structure gradients. With reasonable refractive indexes, this mechanism may allow the generation of signals which cover a wide continuous part of the electromagnetic terahertz range, when used in combination of appropriate detection schemes.

In a recent paper [Phys. Rev. Lett. 94, 197401 (2005)], we introduced a mechanism for creating artificial high refractive index metamaterials by exploiting the existence of sub-wavelength propagating modes in metallic systems. We showed that a perfect metal film with a periodic arrangement of sub-wavelength cut-through slits can be regarded as a dielectric slab with a frequency-independent effective index. Here, we discuss the optical properties of such a system when the perfect metal condition is no longer valid, e.g., in the visible and near infrared wavelength regimes. If the metal obeys a plasmonic dispersion model, we find that films with a periodic arrangement of sub-wavelength slits support two distinct types of guided modes: a surface mode and a set of effective dielectric slab modes. We show how the behavior of both modes is affected by film thickness and surface properties.

The recent theoretical and experimental demonstrations of stop bands for surface acoustic waves have greatly enlarged the potential application field for phononic crystals. The possibility of a direct excitation of these surface waves on a piezoelectric material, and their already extensive use in ultrasonics make them an interesting basis for phononic crystal based, acoustic signal processing devices. In this paper, we report on the demonstration of the existence of an absolute band gap for surface waves in a piezoelectric phononic crystal. The Surface Acoustic Wave propagation in a square lattice, two-dimensional lithium niobate phononic crystal is both theoretically and experimentally studied. A plane wave expansion method is used to predict the band gap position and width. The crystal was then fabricated by reactive ion etching of a bulk lithium niobate substrate. Standard interdigital transducers were used to characterize the phononic structure by direct electrical generation and detection of surface waves. A full band gap around 200 MHz was experimentally demonstrated, and close agreement is found with theoretical predictions.

We consider coupling between free-space and rod-type photonic crystals using semi-analytic 2D methods, and find that for frequencies in the second and third bands this coupling is almost perfect over a large range of angles. We explain this remarkable property in terms of the scattering resonances of the individual inclusions and then confirm the presence of this effect in fully 3D FDTD calculations.

Recently, two-dimensional and three-dimensional periodic dielectric structures have been directly fabricated by laser holographic lithography (HL) to create novel geometric structures with high-precision tolerances. Multiple beam interference via beam splitting mirrors or diffractive optical elements produce isointensity contours that can be accurately recorded in photoresist and subsequently used as a template for creating photonic crystals with a complete or partial bandgap. The periodic structures typically formed by HL comprise of highly convoluted contours that do not conform to typically known geometrical shapes and therefore preclude the use of analytic approaches such as the plane wave expansion (PWE) method to accurately generate the band-dispersion curves. In this paper, we present a numerical technique that decomposes the HL-formed structure into fine mesh grids and expands this material mesh into the PWE method to generate band-dispersion curves. Band diagrams obtained in this way are shown to accurately match the well known solutions for opal, inverted opal, and woodpile structures which have a regular motif. We extend the numerical technique to predict the band structure of HL templates which have an irregular motif and present band diagrams for structures formed by Ar-ion laser phasemask interference.

In order to efficiently model and optimize photonic crystal structures under diffuse light we have to first develop a simulation tool to generate a spatially incoherent source. Here we present a new technique for modeling wide-band spatially incoherent source and implement this technique using finite difference time-domain (FDTD) method. We compare this new method with the conventional method of simulating an incoherent source. We show that this method reduces the computation time by more than one order of magnitude with less than 10% error.

The optical reflectance of photonic-crystal films is revisited, while focussing on the variety of coloration produced by different surface orientations. The needed tools for this analysis are first described. These include a number of simple rules that help locating the useful spectral features of the photonic-crystal reflectance with a minimal knowledge of the structure, and make explicit a full multiple-scattering algorithm (often cited, but not explicitly described so far) for the precise computation of reflectance spectra. It is seen that a face-centered cubic structure of low refractive index can span a wide region of the chromaticity diagram with just a few high-symmetry surfaces.

The FDTD technique is employed to examine the optical properties of 12-fold rotational order quasi-crystal structures. Bandgap and defect states are shown to exits in the quasi-crystal patterns for in-plane propagating light. Out-of-plane propagation is examined by infinitely extending the planar quasi-crystal in the third direction. The resulting micro-structured optical fiber guides show supported modes confined by index guiding. A stack and draw technique is presented making quasi-crystal core designs possible.

Using the transfer matrix method to analyze a 1D anisotropic photonic crystal usually involves a 4×4 matrix, which means for any given ω and β (the Snell quantity nsinθ), four eigenvalues of K can be found. Based on the degeneracy of K, the band edge in the dispersion curves can be divided into two types. One is the regular band edge (R.B.E) which has degeneracy of the order 2 and another is the degenerate band edge (D.B.E) which has fourth order degeneracy. It was predicted that in the case of a transmission resonance in the vicinity of the D.B.E, the resonant field intensity enhancement is proportional to N⁴, where N is the total number of periods, while in the case of a regular band edge, the field intensity enhancement is proportional to N². Based on this prediction, we have calculated the band edge resonant effect of a novel D.B.E photonic crystal structure with a unit cell having two misaligned in-plane anisotropic layers and one isotropic layer. 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, whether the anisotropy is large or small, the field intensity enhancement is approximately proportional to N⁴ once the number of the periods is large enough to cause the strong enough resonance effect inside the structure. We believe this DBE resonant effect will have applications requiring slow-light and in nonlinear optics.

A novel approach for photonic crystals devices analysis, based on perturbation theory is reported. In this method the photonic crystal device is considered as the superposition of a parent lattice and a perturbing one. Then the solution is investigated in terms of the eigensolutions of the parent lattice. This way, one can easily obtain analytic expressions within the first order perturbation, describing the effects of different parameters on the eigensolutions of the structure. The perturbation theory employed in this work is typical of what is conventionally used in quantum mechanics literature. The proposed method is explicit, works fast, and does not involve complicated numerical calculations. Although this approach can be used to obtain some rules of thumb about the eigensolutions of the device within the first order perturbation approximation, it can be further followed to higher order perturbation terms for acquiring any desired level of accuracy. Since the presented method is mostly formulated analytically, not much computational effort is required for analyzing complex structures. In this paper the approach is described in detail and some examples are given to show the usefulness of it.

We present the development of a fabrication technique for a semiconductor-based photonic crystal (PhC) nano-membrane device with reconfigurable active waveguides using micro-electro-mechanical systems (MEMS) technology. This device can be used as a basic building block for optoelectronic integrated circuits that can be reprogrammed for different functionalities such as switches, modulators, time delay lines, resonators, etc. The device is fabricated three-dimensionally on GaAs/Al_x1GaAs/Al_x2GaAs epitaxial layers on a GaAs substrate. The device has a top PhC membrane layer structure composed of hexagonal holes in a triangular lattice. Below that, a separate suspended bridge layer can insert a line of posts into the PhC holes to create a defect line. This MEMS feature can generate/cancel a section of the waveguide in the PhC platform, or (by partial removal) it can change the dispersion of the waveguide. Therefore, the same structure can be used as different types of devices. In this paper, we will discuss detailed fabrication processes for such a multi-layer 3D device structure, including e-beam lithography, inductively coupled plasma reactive ion etching, and multiple steps of regular photolithography and selective wet chemical etching. The unique processing sequence allows us to fabricate the multi-layer 3D device structure from one top surface without regrowth, wafer bonding, or access from the back surface. This simplifies the device processing and reduces the fabrication cost.

While the effective medium theory (EMT) has been useful to explain optical characteristics of a dielectric periodic structure analytically, it has failed to describe metallic structures correctly. In this paper, a fitting-based approach is introduced to applying an effective medium theory to structures that include metallic material. The effective indices of a metallic medium were first obtained by numerically fitting to reflectance characteristics calculated with rigorous coupled wave analysis (RCWA). Searching for an effective medium has been performed through binary searches rather than a time-consuming simulated-annealing algorithm. The calculated effective medium showed results that are in good agreement with RCWA. The deviation was minimal in the long-wavelength limit when angles of incidence, grating depths, or refractive indices of a superstrate are varied. In particular, TE polarization showed more robust features against the variations while TM polarization was more sensitive to the modeling parameters. In terms of the standard deviation, the calculated effective medium was the least affected by the change of grating depths. The applicability of the fitting-based approach was investigated by applying it to a three-dimensional metallic photonic crystal. Simulation results based on the fitting-based EMT perfectly reproduced broad photonic bandgap as observed in published experimental data. Also, the fitting-based approach provided valid results in the wider wavelength range than a traditional EMT.

The fabrication of metallic photonic boxes and their emission properties with black-body radiation at high temperatures are reported. Black-body radiation is modified to enhance the visible spectrum using photonic boxes of about 200 nm. With the structure of resonant cavity and the significantly enhanced density of states at specific wavelengths, the enhanced blue light is observed and it has the peak intensity at 400 nm with 90nm spectral width. Other visible spectra can also be enhanced by simply increasing the size of photonic boxes. Due to the high temperature operation, formation of metallic grain on the surface of photonic boxes is also discussed.

Currently a few hundreds nm dimension is employed to achieve visible and infrared light optical elements for optics field as nano-optics. On the other hand there are a lot of reports of nano-imprint experiment including under 50 nm for storage, bio-technology or semiconductor application. And one of the biggest advantages of nano-imprint is three dimensional fabrications at one imprint procedure. However already introduced two or three dimensional imprinted optical elements are either just confirming replication of conventional Fresnel optics or defect negligible lattice structure. Three dimensional nano-imprint mold (3D-mold) must have great potential for optics fabrication. The combination of 3D-mold and three dimensional nano-imprint method can create flexible optical behavior. Here practical fabrication trials for three dimensional photonic crystal waveguide with 3D-mold and nano-imprint technology are discussed. Particularly fabrication 3D-mold with quarts, nano-imprint methodology and waveguide structure with evaluation and simulation are focused.

Using confocal scanning optical microscopy, we carried out a direct refractive index profiling technique of complex and non-symmetric structured optical fibers. Several improvements on the earlier design are proposed; a light emitting diode (LED) at 658 nm wavelength instead of a laser diode (LD) or He-Ne laser is used as a light source for better index precision, and a simple longitudinal linear scanning and a curve fitting techniques are adapted instead of a servo control for maintaining an optical confocal arrangement. Also, we have developed a novel technique to remove measurement noise generated by pinhole diffraction. This improved, straightforward, and robust method can be used to determine the refractive index profile of optical fibers by determining the reflectivity of a sample's surface. This technique is easy and repeatable, and we demonstrated the refractive index measurement of a core-doped photonic crystal fiber for the first time.

Analytical analysis of straight single-line defect optical waveguides in two dimensional photonic crystals based on expanding electromagnetic fields in terms of Hermite polynomials is reported. This novel electromagnetic field expression is substituted in Helmholtz equation, a new set of linear ordinary differential equations with variable coefficients are obtained, and by employing differential transfer matrix method; defect modes, i.e. the guided modes propagating in the line defect waveguide, are analytically derived. The validity of the results obtained by applying the proposed approach are confirmed by comparing them to those derived by using finite difference time domain method.

In this paper we present the implementation, optimization and commercialization of an ultra-high resolution nano-probe in near field scanning optical microscopy/ spectroscopy (SNOM), nanolithography and high density optical data storage. The theme underlying this effort is the ability to examine or be able to write and/or read ultra fine feature sizes using near field based nano probes. The reason for pursing such research lies in the opportunities it offers for extending the applications of conventional optical microscopy into the nano meter scale domain. Furthermore near-field optical imaging preserves the inherent polarizing, non-invasive, spectroscopic and high temporal resolving capabilities of conventional microscopy, which are absent from other high-resolution techniques

We present our experimental demonstration of self-collimation inside a three-dimensional (3D) simple cubic photonic crystal at microwave frequencies. The photonic crystal was designed with tailored dispersion property and fabricated by a high precision computer-controlled machine. The self-collimation modes were excited by a grounded waveguide feeding and detected by a scanning monopole. Self-collimation of electromagnetic waves in the 3D photonic crystal was demonstrated by measuring the 3D field distribution, which was shown as a narrow collimated beam inside the 3D photonic crystal whereas a diverged beam in the absence of the photonic crystal.

We propose new design parameters for few mode index-guiding holey-fiber (IGHF) that can provide ultra-flattened dispersion properties as well as adiabatic mode transformation capability. A novel silica index guiding holey fiber (IGHF) design is proposed utilizing a new hollow ring structure that is composed of germanosilicate high index ring and hollow air hole imbedded in a triangular lattice structure. The proposed IGHF showed unique modal properties such as nearly zero flattened dispersion over a wide spectral range with low dispersion slope by flexible defect parameter control. It is predicted that ultra-flattened dispersion of 0±0.5ps/(km.nm) from wavelength 1360nm to 1740nm could be achieved with a slope less than 1•10^-3ps/km.nm², along with fine tuning ability of dispersion value. In contrast to prior IGHF, the proposed fibers can be achieved adiabatic mode transformation from annulus mode to a mode generated from solid multi-core fiber due to germanosilicate rings that is highly compatible to LP₀₁ mode in conventional step index fiber. This adiabatic mode conversion of optimized IGHF for ultra-flattened dispersion contributed to low splicing loss, 0.01dB at 1550nm to dispersion compensation fiber.

An optical waveguide for measuring the change of refractive index by using a photonic crystal fiber is designed. The simulation results show that a variation of 0.032 refractive index unit (RIU) could shift the resonant wavelengths of 245nm and 68nm when the refractive indices of liquid are 1.5 and 1.7, respectively. The sensitivity for the refractive index measurement of about 1.3×10^-6RIU is achieved.