We argue that OmniGuide fibers, which guide light within a hollow core by concentric multilayer films having the property of omnidirectional reflection, have the potential to lift several physical limitations of silica fibers. We show how the strong confinement in OmniGuide fibers greatly suppresses the properties of the cladding materials: even if highly lossy and nonlinear materials are employed, both the intrinsic losses and nonlinearities of silica fibers can be surpassed by orders of magnitude. This feat, impossible to duplicate in an index-guided fiber with existing materials, would open up new regimes for long-distance propagation and dense wavelength-division multiplexing (DWDM). The OmniGuide-fiber modes bear a strong analogy to those of hollow metallic waveguides; from this analogy, we are able to derive several general scaling laws with core radius. Moreover, there is strong loss discrimination between guided modes, depending upon their degree of confinement in the hollow core: this allows large, ostensibly multi-mode cores to be used, with the lowest-loss TE₀₁ mode propagating in an effectively single-mode fashion. Finally, because this TE₀₁ mode is a cylindrically symmetrical ('azimuthally' polarized) singlet state, it is immune to polarization-mode dispersion (PMD), unlike the doubly-degenerate linearly-polarized modes in silica fibers that are vulnerable to birefringence.

To date, most design of photonic lattice structures has been based on the use of complex and elaborate models run on high-end computer systems. This work has established that there are several general symmetries, which may result in full 3-D gaps, diamond, inverse face centered cubic and high index contrast simple cubic. The fill fraction is also known to be typically close to twenty five percent high index component. With this knowledge it is possible to come up with a variety of structures which have the same symmetry elements, but the building blocks of which are considerably different from those in the literature. With a reliable fabrication process it is now possible to fabricate a whole range of possible structures in a single run and then experimentally determine if any, in fact, display a gap. We have used this approach to demonstrate an open square structure with the diamond symmetry, three fold interpenetrating FCC structures, sheet structures with the inverse face centered cubic and hexagonal close packed structures, as well as 'stick figure' structures with elements of the inverse FCC or HCP structures. While they have the same symmetry elements as more established structures, these designs may have advantages for particular applications. For example, in the formation of cavities it may be advantageous to employ a structure made up of small discrete sub-units, as opposed to one consisting of 'infinitely long' rods.

One-dimensional (1-D) photonic bandgap (PBG) structures remain one of the most practical ways of applying the PBG concepts to the solution of many urgent problems in laser physics and optical technologies. The sol-gel method is an inexpensive and flexible liquid phase processing technique that is suitable for the deposition of multilayer stacks. The multilayer stacks can be designed as 1-D PBG structures, such as distributed Bragg reflectors (DBR), or single and coupled microcavities, as reported in this work. Spin-coated TiO₂ and SiO₂ layers acted as the high and low refractive index materials, respectively. Each layer was heat-treated at a high temperature (~1000 degree(s)C) for a short period of time (~90 s) in order to increase the index contrast, while preserving relatively smooth interfaces between the consecutive layers. Ellipsometry, X-ray diffraction, micro-Raman spectroscopy, transmittance/reflectance spectroscopy, and atomic force microscopy were used to characterize both the individual layers and the whole structures. Strong PBG properties are demonstrated, with an omni-directional stop band for a 5.5-pair DBR ((lambda) equals 550 - 600 nm, gap to mid-gap ratio equals 7.6%) and sharp pass bands within the stop bands for the microcavities.

This paper reports a new method for faceting artificial opals based on micromanipulation techniques. By this means it was possible to fabricate an opal prism in a single domain with different faces: (111), (110) and (100), which were characterized by Scanning Electron Microscopy and Optical Reflectance Spectroscopy. Their spectra exhibit different characteristics depending on the orientation of the facet. While (111)-oriented face gives rise to a high Bragg reflection peak at about a/(lambda) equals 0.66 (where a is the lattice parameter), (110) and (100) faces show much less intense peaks corresponding to features in the band structure at a/(lambda) equals 1.12 and a/(lambda) equals 1.07 respectively. Peaks at higher energies have less obvious explanation.

In this contribution, a method to fabricate a diamond structure with a complete PBG in the near infrared is proposed. The procedure starts by building an opal composed of two types of microspheres (organic and inorganic) in a body-centered-cubic symmetry by means of a micro-robotic technique. Then, the organic particles may be selectively removed to obtain a diamond structure of inorganic particles. Once this structure is assembled its filling fraction may be controlled by sintering. Subsequently this template can be infiltrated with an adequate high refractive index material. In this way, the method can be extended to make diamond inverse opals of, for instance, silicon with gap to mid gap ratios as large as 13% for moderate filling fractions. An overview of micromanipulation as well as previous experimental results will be offered to show the feasibility of this method.

Photonic crystal integrated circuits offer a range of possibilities for manipulating the propagation of light. Here, we demonstrate two different systems, i.e. superprisms and coupled cavity waveguides, that allow dispersion engineering in space and time, respectively.

Planar photonic crystal structures are a new way to achieve the confinement and guiding of light in an optical circuit. Acceptably low levels of optical loss will be key to developing this technology into commercially viable devices. Meaningful measurement of the loss of these devices is complicated by their reduced size and their optical model structure. To date no satisfactory loss measurement of these waveguides has been made. We analyze the challenges to be reached that will lead to accurate and quantitative measurements.

Dielectric periodic media can possess a complex photonic band structure with allowed bands displaying strong dispersion and anisotropy. We show that for some frequencies the form of iso-frequency contours mimics the form of the first Brillouin zone of the crystal. A wide angular range of flat dispersion exists for such frequencies. The regions of iso-frequency contours with near zero curvature cancel out diffraction of the light beam, leading to a self-guided (self-collimated) beam.

We present a systematic method for designing electromagnetic modes in dielectric-core photonic crystal optical waveguides. We show that the guided modes of the photonic crystal waveguides are mainly confined to the guiding region. The properties of these modes can be modified by changing the geometry of the air holes next to the guiding region. We show how this concept can be used to design single-mode photonic crystal waveguides. We also describe a method for changing the slope of the dispersion diagrams of these guided modes.

Transmission of light through linear defects in two-dimensional (2D) photonic crystals has been already successfully demonstrated in two ways: numerical simulations and experimental measurements. Recently, novel waveguides have been proposed in which the propagation of photons is performed via hopping due to overlapping between nearest-neighbors defect cavities. These waveguides are commonly referred to as coupled-cavity waveguides (CCW). In this work, we present a comprehensive analysis of the light transmission (TM modes) in CCW's created in hexagonal 2D photonic crystals made of high-index dielectric rods. Numerical simulations of the transmission are performed using a 2D Finite-Difference Time-Domain method. A plane wave algorithm and a simple one-dimensional (1D) tight-binding model are employed to describe the miniband which allows the light transport. It is shown that modifying the individual cavities along the CCW one can control the average frequency and the dispersion relation of the miniband. The results also show that this novel guiding method can be used to develop 1310nm/1550nm Coarse-WDM optical demultiplexers employing bended waveguides.

We experimentally demonstrate the structural tuning of the waveguiding modes of line defects in photonic crystal slabs. By tuning the defect widths, we realized efficient single-mode waveguides that operate within photonic band gap frequencies in SOI photonic crystal slabs. The observed waveguiding characteristics agree very well with 3D finite- difference time-domain calculations. The propagation loss of the line defect waveguides is experimentally determined to be 6 dB/mm. In addition, we measure group velocity dispersion of line defects by using Fabry-Perot resonance of the sample. Extremely large group dispersion is observed, and the traveling speed of light is reduced down to 1/100 of the light velocity in air.

We investigate the localized coupled-cavity modes in two- dimensional dielectric photonic crystals. The transmission, phase, and delay time characteristics of the various coupled-cavity structures are measured and calculated. We observed waveguiding through the coupled cavities, splitting of electromagnetic waves in waveguide ports, and switching effect in such structures. The corresponding field patterns and the transmission spectra are obtained from the finite- difference-time-domain (FDTD) simulations. We also develop a theory based on the classical wave analog of the tight- binding (TB) approximation in solid state physics. Experimental results are in good agreement with the FDTD simulations and predictions of the TB approximation.

We describe a multipole theory of photonic crystal or more generally microstructured optical fibers (MOF). We review basic MOF properties such-as losses and number of modes-obtained with our method and expose considerations and results on dispersion management taking into account the losses.

We report the fabrication process for several types of photonic crystal fibers (PCFs), which enables mass-production with a 125micrometers diameter. Five layers of silica capillary tubes having 2 mm inner and 3 mm outer diameters were stacked in a hexagonal pattern around a silica rod of a 3 mm diameter. By jacketing a large silica tube around the tube stack, the preform for a PCF was obtained. Another type of PCF was made by stacking four tubes in one layer, which had 6 mm inner and 8 mm outer diameters. In order to draw PCFs from both types of preforms, a drawing tower for conventional fibers was used. In the beginning of the drawing process, the temperature was set to be the running temperature for the conventional fiber, and then lowered by a couple of hundreds degrees. The optical properties of the fabricated PCFs were measured with various hole sizes and pitches. These include the intensity distribution of the guided beam that was a single mode at 1550 nm, and the transmission loss measured by using the cut back method, and the fundamental mode cut-off characteristic at a short wavelength, and the numerical aperture measured at several wavelengths by using the far field patterns.

We show that introducing anisotropy into periodic dielectric structures leads to new optical phenomena as well as to a new approach to a variety of applications. One-dimensional anisotropic structures allow a new type of chiral twist defect resulting in a localized photonic mode with unusual properties. Unlike isotropic layers of alternating index of refraction, where the periodicity can be destroyed only by changing the refractive index or thickness of a layer, a defect can be created in anisotropic media by introducing an additional rotation between consecutive layers. Computer simulations show that introducing an additional rotation in the middle of a sample with cholesteric ordering produces a localized state whose frequency can be tuned from one edge of the photonic stop band to the other by varying the angle of rotation from 0 to 180 degrees. Most of the energy of this mode exists as a circularly polarized standing wave with the same handedness as the structure, independent of the polarization of the exciting wave. This localized mode gives rise to a crossover in the nature of propagation. Below a crossover thickness, the localized mode is excited only by a wave with the same handedness as the structure and exhibits a peak in transmission at the defect frequency. Above the crossover, however, the defect mode can be excited only by the oppositely polarized wave and a resonant peak appears in reflection. Simulations for lengths below the crossover are in agreement with measurements of microwave transmission through stacks of overhead transparencies, ordered in the same way as the molecular layers of a cholesteric liquid crystal. Three types of defect are introduced: (1) an additional 90 degrees rotation, (2) an additional 45 degrees rotation, and (3) a combination of a 45 degrees rotation and a quarter-wavelength separation.

Semiconductor three- and two-dimensional photonic crystals and their effects on the control of photons are investigated for possible applications to optical chip and functional devices. On the three-dimensional crystal, the effect of the introduction of light-emitter into the three-dimensional photonic crystal is investigated, and also the design of single defect cavity is performed, which is important for the development of the optical chip. On the two-dimensional photonic crystals, an ultra-small channel-drop-filtering device using unique phenomena of trapping and emission of photons by single defects in the 2D photonic crystal slab is described. These results encourage us to develop ultra-small optical integrated circuits using photonic crystals.

Metals form interesting 2-D photonic crystal structures due to their ability to support surface plasmon modes. Recent research has highlighted the potential of photonic crystal concepts to control these modes, in particular due to the sub-wavelength confinement of their fields. We have already demonstrated that a full photonic bandgap for surface plasmons can be achieved through periodic nano-structuring of the surface. Using similar techniques photonic bandgap waveguides for surface plasmons have recently been reported, confirming the viability of metal based photonic crystal surfaces. To utilize these photonic crystal surfaces it is vital that one can efficiently couple radiation both into and out of the surface plasmon mode. Owing to the intrinsic loss of metals such coupling must take place over short distances if it is to prove effective. We have fabricated a metallic photonic crystal surface specifically to explore the efficiency of this coupling. We will show that efficient coupling can be achieved for all surface plasmon propagation directions. Further, for the structures we examined we found that surface plasmon coupling efficiency to radiation was typically 70%. We have also measured the propagation distance required for such coupling, and will discuss the implications our results have for photonic crystal devices based on metallic surfaces.

Novel square lattice photonic band gap lasers are realized at room temperature from single cell photonic crystal slab micro-cavities fabricated in InGaAsP materials emitting at 1.5 micrometers . This single cell photonic band gap laser operates in the new class of two-dimensional mode to be classified as the smallest possible whispering gallery mode with genuine energy null at the center. The low-loss nondegenerate mode with modal volume of 0.1 ((lambda) /2)³ demonstrates a spectrometer-limited below-threshold quality factor > 2000 and a theoretical quality factor of > 10,000. Threshold incident peak pump power of 0.8 mW is achieved from this whispering-gallery-type laser mode. The other class of photonic crystal lasers is also observed outside the photonic band gap of the square lattice, operating in the mode characteristically one-dimensional.

It is shown that microwave radiation can be transmitted through a wall of aluminum-alloy bricks even though the width of the gaps between the metallic elements is less than 5% of the radiation wavelength. Up to 90% of the radiation made incident upon the wall is transmitted, with both linear polarizations being passed. Experimental results are compared to theoretical predictions. Proving that the transmission mechanism relies upon self-coupled surface plasmon resonances in what are effectively Fabry-Perot cavities.

We express the quality factor of a mode in terms of the Fourier transforms of its field components, and prove that the reduction in radiation loss can be achieved by suppressing the mode's wave-vector components within the light cone. Although this is intuitively clear, our analytical proof gives us insight into how to achieve the Q factor optimization, without the mode delocalization. We focus on the dipole defect mode in free standing membrane and achieve Q > 10⁴, while preserving the mode volume of the order of one half of cubic wavelength in material. The derived expressions and conclusions can be used in optimization of Q factor for any type of defect in planar photonic crystals.

We survey basic quantum optical processes that undergo modifications in photonic crystals doped with resonant atoms: (a) Solitons and multi-dimensional localized 'bullets' propagating at photonic band gap frequencies. These novel entities differ substantially from solitons in Kerr-nonlinear photonic crystals. (b) Giant photon-photon cross-coupling that can give rise to fully entangled two-photon states. We conclude that doped photonic crystals have the capacity to form efficient networks for high-fidelity classical and quantum optical communications.

We have measured quality factors as high as 4000 for cavity resonances at 1.3 eV in photonic crystal microcavities formed by removing seven holes. In this paper, we discuss the prospect of coupling a single optical mode of a photonic crystal microcavity to the single-exciton (1X) level of a semiconductor quantum dot.

Second harmonic generation (SHG) in Cerenkov configuration is investigated under conditions for which the use of a linear grating fabricated on top of the waveguide reproduces a photonic band-gap structure. The fundamental mode of the guide, at the fundamental frequency, is tuned at the photonic band edge resonance thus experiencing a great confinement and enhancement of the electromagnetic field inside the structure. The conversion efficiency achieved in both forward and backward direction is at least one order of magnitude greater than that of a 'conventional' Cerenkov emission in a waveguide of the same length.

We investigate femtosecond pulse propagation in photonic crystal fiber, reporting the generation of tunable femtosecond soliton pulses. For sufficiently broad spectral content, stimulated Raman scattering transfers energy from the higher frequency spectral components to lower frequencies, resulting in a continuous self-frequency shift to longer wavelengths. Power dependent spectral analysis reveals a well-formed soliton at peak powers exceeding 100 W. Background-free intensity autocorrelation measurements confirm soliton formation with a duration of < 90 fs and with an energy conversion efficiency of 60%. Numerical solutions were performed based on a generalized nonlinear Schrodinger equation that included the effects of dispersion, self-steepening, optical shock formation, self-phase modulation and stimulated Raman scattering. The resulting spectra from the simulations are in excellent agreement with the measured spectra, and are consistent with the intensity autocorrelation measurements.

The emission of a dipole in a finite-thickness photonic band gap structure is investigated. The dipole is located at a large value of the local density of states and its wavelength is taken at the edge of a full band gap. The resulting emission is highly enhanced and is confined in a small angular region. This is confirmed numerically for two different structures designed from two different tree-dimensional crystal: the woodpile and the simple cubic photonic crystals.

When rows of cylinders are periodically removed from a hexagonal array of dielectric cylinders, a new two-dimensional (2D) photonic crystal (PC) arises. The new structure consists of a lattice of vacancies embedded in the initial hexagonal lattice. We called it Suzuki Phase because it remains similar structures discovered in the 60's by K. Suzuki studying alkali halides. A plane-wave algorithm as well as a 2D finite difference-time-domain method has been employed to study the photonic properties of this PC as a function of the filling fraction (f) in the case of high dielectric cylinders ((epsilon) equals 13.6) in air. For TM- modes, it is shown that in a certain range of f an isolated miniband appears in the gap of the initial hexagonal lattice. The miniband, which is created by the coupling of defect states, is described by a tight-binding formalism with two parameters. Also, the frequencies of the two possible vacancy defects in the SP have been obtained and their symmetry analyzed.

In this article, the transfer matrix method (TMM) is modified for study of optical wave propagation in layered media with conducting interfaces. Both the TE and TM mode transfer matrices are presented and their properties are discussed. The application of the modified TMM to study of propagation in a Kronig-Penny photonic crystal is explained. The practical realization of a Kronig-Penny photonic crystal through heterostructures with conducting interfaces is also demonstrated.

In an experimental demonstration, we've observed some kinds of polarization properties in Optical Diffraction Grating. Trying to explain such observation, we are made to travel back into basic optics principles. We can see that neither classical theory nor mathematical formalism of Quantum- mechanics can deliver an enough bright visual perception about what's happening in atomic-scales causes polarization. But Quantum-Photonics will be able to describe the gradual and partial polarization effects in submicron scales. It consists of both physical description and mathematical formalism for optical phenomena in atomic scales based on particle nature of light.

When the unit cell of the photonic crystal contains material which undergoes an optical Kerr effect, internal illumination will change the refractive index distribution without modifying the crystal periodicity and induce significant modifications of the dispersion relations. We describe these modifications by a self-consistent computation of the band structure where the occupation of a photon mode with specific frequency, Brillouin-zone vector and polarization is kept fixed. This requires to solve a sequence of ordinary, linear, photonic band structure problems. The resulting non-linear photonic band structure explicitly depends on the mode occupation, itself determined by the level of illumination. We carry out specific non-linear band structure calculations for the woodpile structure where rods are considered experiencing refractive index changes according to various types of illumination. It is shown that, for positive Kerr coefficient, a strong illumination moves the photonic band gap to lower frequency while slightly modifying its width. The use of different illumination polarizations and frequencies results in modifications of the band structure and the spectral location of the Van Hove singularities in the density of states.

A two-dimensional (2-D) photonic band gap (PBG) structure was utilized for the temperature mapping of ultra-small structures, such as microelectromechanical systems (MEMS). Optical properties of GaAs were considered in the design of the device since GaAs is nearly transparent and lossless in the chosen infrared region, and also has a reasonably high dielectric constant of 11.4. The structure consist of a triangular lattice of air holes etched into GaAs, with a lattice constant, a, of 0.382-micrometers , including one linear waveguide and three isolated point defects with radii 0.51 a, 0.54 a, and 0.57 a, respectively. The operational principle of the device is based on guiding and selecting the specifically tuned wavelengths through the corresponding point defects. It has been sown that having processed the intensities, obtained from each defect, in accordance with the blackbody radiation characteristics and the transmission properties of the device, the temperature reading of the target in concern can be obtained. Despite many studies concerning guided modes in 2D PBG materials, few sensor applications exist in the literature. Future work on defects, taking advantage of strongly directional behavior, frequency selectivity and specific polarization, will highlight the much richer possibilities of the PBG technology for novel applications in the fields from optical MEMS to quantum computing.

A photonic crystal efficiently controls the radiation rate of an embedded dipolar emitter. The influence of the periodic refractive index patterning on the emitter characteristics is assessed and the efficiency of a dipolar photonic source is calculated for a realistic, three-dimensional photonic crystal. Taking as a starting point the photonic band structure, it is shown that the emission rate is strongly correlated with the density of modes. For an infinite crystal, the computation of the field propagator confirms, in particular, that the emission rate falls to zero in the frequency range defined by the photonic band gap. We specifically consider a photonic crystal with a woodpile structure, offering a wide gap, with a monochromatic oscillating dipole at specific points (in or outside the rods) and orientations in the structure, and compute the emitted fields, expanded in terms of the photonic crystal eigenmodes. Radiation rate enhancements or inhibitions are predicted, according to the frequency and to the direction of the emission.

A great deal of interest has been generated in Photonic Crystal Fibers (PCF) due to its unique propagation characteristics as it offers single mode operation in a wide wavelength range, large mode field diameter and manageable dispersion properties. PCFs are single material optical fibers with a periodic array of air holes running down the length of fiber. The arrangement and spacing of air holes provide freedom to tailor the dispersion properties for telecom applications. Therefore PCFs are expected to be integrated with the existing optical fiber technology. As a result, splicing characteristics of PCF with conventional single mode fiber or with PCF of different air hole spacings, is needed to be evaluated. In this paper, we report the analytical techniques and simulation for the estimation of Splice Loss of PCF with PCF of different geometry, and with conventional fiber. Variation of Splice loss due to normalized transverse offset of two PCFs for different ratios of air hole spacing is obtained. It is observed that the splice loss depends on air hole spacing of PCF and V-value of conventional fibers.

A cholesteric liquid crystal cell was fabricated possessing 1-D photonic bandgap structure. From the measurement of the linear absorption spectrum of the cell, a bandgap was identified, centered at 1.08 eV (1143 nm) with the gap width of 0.1 eV (100 nm). Based on the linear absorption spectra, the dispersion of the principal refractive indices along the parallel and perpendicular directions of the molecule was determined as 1.631 and 1.476 at the wavelength of 1064 nm through Berreman matrix method. A Q-switched Nd:YAG laser (1064 nm) was employed to investigate the nonlinear optical changes of photonic bandgap. As the laser intensity was increased to 320 MW/cm², the transmittance decreased from 0.51 to 0.47, corresponding to an 8% change. The nonlinear transmittance change was analyzed numerically by Berreman matrix method with the incorporation of Kerr nonlinearity in the optical response of the molecules forming cholesteric liquid crystal. The changes in the refractive indices along the parallel and perpendicular directions were 3.46 and 1.51 X 10^-10 (cm²/W). The changes in the position and width of bandgap were 0.02 eV and 0.03 eV at the laser intensity of 320 MW/cm².

Photonic band gap interaction between surface plasmon (SP) and dielectric gratings is calculated by rigorous coupled wave analysis (RCWA). Results from the RCWA show that the reflectance goes down near to 0%, and the diffraction efficiency increases above 50% even though the modulation depth of the grating layer is less than 100nm. If the grating vector is twice of the wave vector of SP, on the other hand, the reflectance surprisingly increases up to 90% even though the resonance condition of the SP is satisfied. This photonic band gap effect at the SP resonance can be completely analyzed by the RCWA, and verified by experiment.

We show that a photonic crystal can be designed as a passive field-of-view expander of optical receivers. In other words, light received at different angle within a given angular range is adjusted to propagate within a smaller angular range when exiting the device and illuminating the actual detector. We plan to employ that function in receivers for optical free-space communications and propose an approach for suppressing beam wander and scintillation of the focal spot on the detector due to the wavefront distortions. Since the alignment of the propagation direction is performed in a passive way, the beam adjustment to stabilize the coupling efficiency of the detector is delay-free. We describe here the idea of this approach in order to show how to utilize effectively the anomalous dispersion characteristics of photonic crystals. In our approach, the photonic crystal behaves like a homogeneous medium with a refractive index less than 1. We discuss the design of photonic crystal structure with such an optical characteristic, and first predict the propagation angle of the beam after passing through the crystal using the dispersion characteristic. Then this prediction is confirmed by electromagnetic analysis using the FDTD (finite-difference time-domain) method. Finally we present a simplified optical setup for the receiver.

We have developed an finite-difference time-domain program that can analyze photonic devices with gain and/or dispersion. As an example, a two-dimensional photonic-crystal laser is simulated. The simulation can show the relaxation oscillation behavior at extremely high current injection.

We describe a novel microfabrication method based on interference of several coherent laser pulses in photosensitive media. The method allows to transform the periodic multidimensional interference patterns into periodic modulation of dielectric properties of the material, and is therefore potentially suitable for the photonic crystal fabrication in materials like photoresists, photosensitive glasses, and others. We have fabricated one, two, an three-dimensional photonic crystals with different lattices and sub-micrometer periods. The fabricated structures have high structural quality, as evidenced by confocal and scanning electron microscopes. Furthermore, using numerical simulations we explore the possibilities to obtain body-centered-cubic and diamond photonic crystal lattices by varying optical phases of the interfering beams. Numerical simulations are also used to reveal photonic bandgap properties of some 2D photonic crystals, fabricated using this technique.

In this paper, we report on the design, modeling, fabrication, and characterization of an amorphous silicon microcavity. The microcavity is fabricated using a one-dimensional photonic bandgap structure. The structure was grown by plasma deposition method. Quarter wavelength thick stacks of hydrogenated amorphous silicon nitride and hydrogenated amorphous silicon oxide were consecutively deposited using low temperature plasma enhanced chemical vapor deposition. For the characterization of the dielectric microcavities the intrinsic photoluminescence of the amorphous silicon is used. Bulk amorphous silicon has a luminescence bandwidth of 250 nm. Due to the presence of the microcavity, the luminescence is enhanced by at least an order of magnitude at the resonance wavelength of 700 nm. Additionally, the luminescence is inhibited in the photonic bandgap occupying a spectral band of 150 nm. The microcavity resonance has a quality factor of 120 corresponding to a luminescence linewidth of 6 nm. The enhancement of the photoluminescence is understood by the modified photon density of states of the dielectric microcavity.

We design a micro-scale wavelength-division-demultiplexing device based on the anomalous dispersion and band gaps in photonic crystals. We first calculate the band structures needed for the analysis of the anomalous dispersion, using the finite-difference time-domain method with periodic boundary conditions. Then a simple wavelength demultiplexer is designed and simulated by use of these results. The designed demultiplexer is composed of two photonic crystal structures that have different cylinder radii and are in close contact with each other. From the computed results, the possibility of micro-scale photonic crystal demultiplexers is demonstrated.

We design a 1 X 4 optical splitter made of photonic crystal waveguides and analyze the properties of the optical splitter using the finite-difference time-domain method. Our simulation results show that the transmission properties vary with bend geometries and wave frequencies. Additionally we perform numerical simulations of T-shaped waveguide branches in the splitter to reduce the reflections at the T- branches. The improvement of transmission is achieved by placing the defects of extra rods in the branching region.

Theory of coupled photonic crystal for both synchronous as well as asynchronous waveguided systems is presented. Techniques for analyzing symmetric (even) and anti-symmetric (odd) polarized modes in coupled photonic crystals waveguides are presented. Techniques used include plane wave expansion method (PWM) and finite difference time domain (FDTD). Results obtained from both techniques are shown to be in good agreement. Applications presented include, frequency selective filter, splitter, and switch.

A photonic band gap is determined by its boundaries, which are frequently computed by the Rayleigh-Ritz method, with the plane wave or the finite element basis functions. This method produces a sequence of upper bounds. Since there are no error estimates available on these approximations, the extent of the band gap is not accurately determined, particularly as this method is also known to suffer from a poor rate of convergence for the cases of interest. We adopt the method of intermediate problems to develop a procedure to calculate the lower bounds to the photonic band gap edges. The lower and the upper bounds supplement each other to determine a band gap with arbitrary accuracy, which is essential for designing the photonic band gap material. Computation of the lower bounds requires only slightly more effort than the upper bounds to produce the approximations with comparable accuracy. An alternative method to determine upper bounds is also developed in the process.