This PDF file contains the front matter associated with SPIE Proceedings Volume 7223, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

We present the analysis and design of three-dimensional photonic crystal demultiplexers in which the simultaneous existence of the superprism effect and the diffraction compensation results in a compact structure. First, we report on a diffractive index model developed to facilitate the simulation of the beam propagation in three-dimensional photonic crystals. Then, we use tetragonal woodpile photonic crystals to design a demultiplexer.

The potentials of integrated optical systems for implementing compact and low power consumption yet highly sensitive sensing systems have made them a viable candidate for integrated chemical and biological sensing applications. In these integrated optical sensing systems, spectrometers have a significant role as a building block that enables on-chip spectral analysis. Monitoring the spectral features of the signal using an on-chip spectrometer brings about a variety of new sensing mechanisms and architectures in an integrated platform. Monitoring absorption spectra, measuring Raman emission features, and tracking changes in spectral signatures as a result of environmental changes are some of the schemes made possible by such spectral analysis. In this work, we implement superprism-based photonic crystal devices in planar platforms as on-chip spectrometers. We use planar silicon platform in a silicon-on-insulator (SOI) wafers for the infrared wavelength range. A silicon-nitride (SiN) planar platform is used for the near infrared and visible wavelength ranges. In both SOI and SiN implementations, superprism-based spectrometers are experimentally demonstrated and compared with grating spectrometers made in the same platform. The potentials of the demonstrated spectrometers to meet the requirements of current and future applications in integrated optical sensing are briefly discussed.

Low power operation and high speed have always been desirable in applications such as data processing and telecommunications. While achieving these two goals simultaneously, however, one encounters the well-known powerbandwidth trade-off. This is here discussed in a typical bistable switch based on a two-dimensional photonic crystal with Kerr type nonlinearity. The discussion is supported by the nonlinear finite difference time domain (FDTD) simulation of a direct coupled structure with a home-developed code. Two cases of working near resonant and offresonant are simulated to compare the power and the speed of the device in the two cases. It is shown that working nearresonance reduces the power levels at the expense of reducing the settling time, i.e. the bandwidth limitation. The hystersis loops for the device are also obtained with both coupled-mode theory and quasi-steady state FDTD simulation. The impact of operating near/off resonance on the shape of the hystersis loop is discussed as a confirmation of the previous results. Alternative ways of reducing the power while saving the bandwidth are also examined. The discussion is general and one may investigate other optical switches to obtain similar results.

In order to create three-dimensional (3D) photonic crystals (PCs) with large photonic bandgap properties (PBG), it is necessary to control the 3D fabrication with desired symmetry, high index contrast, and high structural stability. To rational design the 3D photonic structures fabricated by holographic lithography, we have conducted quantitative analysis to study structural distortion during each processing step and their impact to PBG. Because of the relatively low dielectric contrast between typical polymers and air, the directly patterned polymer structures are usually used as templates for backfilling of high-index materials, followed by removal of the polymer template to realize complete PBGs. Therefore, the fidelity of the final PCs is critically dependent on the thermal and mechanical robustness of the polymer templates, the deposition methods (e.g. dry chemical vapor deposition vs. wet chemistry), and the template removal procedure. Here, we address these challenges using different photoresist systems and deposition methods to create Si and titania 3D PCs.

Photonic crystal (PC) devices in the InP/InGaAsP/InP planar waveguide system exhibiting narrow bandwidth features were investigated for use as ultrasmall and tunable building blocks for photonic integrated circuits at the telecom wavelength of 1.55 μm. The H1 cavity, consisting of a single PC-hole left unetched, represents the smallest possible cavity in a dielectric material. The tuning of this cavity by temperature was investigated under the conditions as etched and after the holes were infiltrated with liquid crystal (LC), thus separating the contributions of host semiconductor and LC-infill. The shift and tuning by temperature of the MiniStopBand (MSB) in a W3 waveguide, consisting of three rows of holes left unetched, was observed after infiltrating the PC with LC. The samples finally underwent a third processing step of local wet underetching the PC to leave an InGaAsP membrane structure, which was optically assessed through the ridge waveguides that remained after the under etch and by SNOM-probing.

Phononic crystals are two- or three-dimensional periodic structures that are composed with two or more materials with different elastic constants, giving rise to complete band gaps under specific conditions. Band structures are usually employed to describe infinite phononic crystals, as they provide one with all propagative waves in the periodic medium, or Bloch waves. It is however well known that evanescent waves must be considered in propagation problems whenever scattering, diffusion, or diffraction by a finite object are involved. We have extended the classical plane wave expansion (PWE) method so that it includes complex wave vectors in the direction of propagation at a fixed frequency. The new complex PWE method has been used to generate complex band structures for two-dimensional phononic crystals. Both propagative and evanescent solutions are found at once. This method of analysis is expected to become the basic building block to solve scattering problems in phononic crystals, yielding naturally diffraction efficiencies, as is illustrated with an example. In addition, it directly gives the eigenfrequency contours that are required to understand refraction (positive or negative) in phononic crystals.

Using the finite difference time domain method, we investigate theoretically the band structure and phonon transport in a phononic crystal constituted by a periodical array of cylindrical dots deposited on a thin plate of a homogeneous material. We show that this structure can display a low frequency gap, as compared to the acoustic wavelengths in the constituent materials, similarly to the case of locally resonant structures. The opening of this gap is discussed as a function of the geometrical parameters of the structure, in particular the thickness of the homogeneous plate and the height of the dots. We show the persistence of this gap for various combinations of the materials constituting the plate and the dots. Besides, the band structure can exhibit one or more higher gaps whose number increases with the height of the cylinders. The results are discussed for different shapes of the cylinders such as circular, square or rotated square. The band structure can also display an isolated branch with a negative slope which can be useful for the purpose of negative refraction phenomena. We discuss the condition to realize wave guiding through different types of linear defects inside such a phononic crystal. Finally, we investigate the phonon transport between two substrates connected by a periodic array of dots. We discuss different features appearing in the transmission spectra such as the Perot-Fabry type oscillations related to the height and the nature of the dots, the existence of transmission gaps related to the period and the nature of the substrate, the possibility of a narrow transmission peak close to a zero of transmission.

Lamb wave propagation in a surface-stubbed phononic-crystal plate is investigated numerically and experimentally. Results show that the complete band gaps and flat bands of elastic waves exist in the structure. By using laser ultrasonic techniques, the experimental measurements demonstrate the evidence of the band gaps and resonances at the band-edge frequencies. In addition, a frequency range associated with the deaf bands is found. Based on the verified band gaps and deaf bands, waveguiding effects in the structure with a line defect are characterized. Furthermore, a sharply bent waveguide is then designed and fabricated to experimentally demonstrate frequency selection for broadband Lamb waves.

By creating line defects cavities in the structure of a phononic crystal (PC) made by etching a hexagonal (honeycomb) array of holes in a 15μm-thick slab of silicon, high-Q PC resonators are fabricated and tested using a complimentary-metal- oxide-semiconductor-compatible process. The radii of the holes are approximately 6.4μm and the spacing between nearest holes is 15μm. We show that the complete phononic band gap of the PC structure supports resonant modes with quality factors of more than 6000 at frequencies as high as 126MHz in the resonator structure. The very good confinement of acoustic energy is achieved by using only a few PC layers confining the cavity region. The calculated frequencies of resonance of the structure using finite element method are in a very good agreement with the experimental data. The performance of these PC resonator structures makes them excellent candidates for wireless communication and sensing applications.

The Talbot effect refers to the self-imaging property of periodic structures illuminated by collimated, coherent light. Complex periodic and quasi-periodic irradiance distributions are formed in three-dimensional (3-D) space near the gratings through diffraction and interference. A wide variety of novel irradiance distributions can be synthesized through design of the grating structures. These irradiance distributions can be converted into dielectric structures through exposure of photosensitive materials and subsequent processing or, alternately, can serve as inspiration for photonic crystals to be fabricated through other techniques. In this paper, we explore the dispersion properties of a rhombus lattice photonic crystal structure inspired by the fractional Talbot effect. These "Talbot crystals" are used to demonstrate potential for broadband "all-angle" self-collimation for waveguide and optical multiplexing applications. Additional directions for future research will also be discussed.

A complete photonic band gap (PBG) in photonic crystal slab (PCS) devices is desirable for various applications, and a realizable device of this kind demands minimal transmittance in-plane as well as out of plane. While in the past much work has considered this problem, none have held transverse confinement as a prime factor. In order to achieve our goal, square and triangular hole shapes are considered. Looking at sharp featured shapes as well as their fabrication realizable rounded counterparts and an even more rudimentary triangular cluster of circles, we look to break the crystalmode symmetries for TM photonic bands and, therefore, open a complete band gap between the 1st and 2nd bands for both TE and TM light. TE/TM gap overlap is optimized for single-slab-mode operation, via the effective index method, for hole size, hole orientation, and slab thickness - all as functions of the lattice constant, a, and operational wavelength, λ. It is found that rounded triangular holes and tri-clustered circular holes of size 0.88a and thickness d/λ = 0.112 show identical photonic behavior that provides an optimized gap overlap of 0.0496 (ωa/2πc = a/λ) with a 12.81% gap figure of merit (Δω/ω₀).

Numerical methods, such as the finite difference time domain (FDTD) technique, are commonly used to study transmission properties, waveguide modes, and localized states of photonic crystals and photonic quasi-crystals. The degree to which a localized state is excited is dependent on the source's topology. Researchers have proposed a number of different source configurations in order to efficiently excite localized states; dipole sources, random sources, and initial field distributions. The efficient excitation of different localized states in a photonic crystal and quasi-crystal through a general source configuration remains an issue to be addressed. This work re-examines the techniques currently used and determines the most efficient method to excite the modes of a photonic crystal and quasi-crystal without prior knowledge of the localized state profiles.

This paper derives a new fundamental equation for the frequency spectra ω(q) of one-dimensional photonic crystals as a function of Brillouin wave vector q in the form of a novel factored expression, tan² qd / 2 = tan(k_Na_N -α_N) × tan(k_Na_N - β_N), where N the number of layers per period is, d is the unit cell width, and k_i = n_iω/c is the local wave vector in the ith layer of width 2a_i and refractive index n_i. Angles(α_N,β_N) depend on the parameters of all N layers but are independent of a_N . For two layers, (α₂, β₂) correspond to the even/odd parity solutions at the center and the edge of the Brillouin zone. The derived spectral expression provide separate eigenvalue conditions for consecutive band edges at the center and the edge of the Brillouin zone for any N and is useful in finding the Bloch phase that is necessary in finite crystal calculations. The formalism is convenient for tailoring band gaps and for calculating impurity modes in dielectric stacks.

It has been theoretically predicted and experimentally shown that circular coaxial aperture arrays have higher transmissivities with respect to simple circular ones. This observation is mainly attributed to the propagating waveguide modes supported by the circular coaxial unit cell. In this letter, we investigate extraordinary light transmission in simple rectangular and coaxial rectangular aperture arrays through decaying TE waveguide modes at mid-infrared wavelengths. We demonstrate enhanced transmissions for the rectangular coaxial aperture arrays with respect to simple ones indicating that the enhancement of extraordinary light tranmission in coaxial structures can not be simply explained by the presence of propagating waveguide modes. Using 3-D FDTD simulations and experimental analysis of the localized plasmons at the aperture rims of the individual apertures, the nature and the enhancement of extraordinary light transmission for the coaxial apertures are shown. Shape anisotropy of the apertures is utilized for polarization control of the transmitted light through the total suppression of the desired polarizations. Depolarization ratios larger than the commercially available holographic wire grid polarizers are obtained. The reported results indicate the underlying physics of enhanced extraordinary transmission in coaxial aperture arrays is intricate and merits further scientific attention while practical applications are possible through the controlling of the aperture shapes.

A novel plane-wave-based approach for analytical treatment of dispersive relation is developed and applied to analyze the behavior of electromagnetic waves in plasmonic-photonic-crystal slabs. Here Drude model is used for describing frequency dependent permittivity of plasma rods in host dielectric medium. In the present work, dispersion relation below and above the light line is calculated approximately by means of Maxwell-Garnett effective medium and Revised Plane Wave Method (RPWM). The eigen-functions are then used in Revised Guided Mode Expansion (RGME) as the set of orthonormal bases. Following this procedure, the accurate band structure is obtained. In these kind of methods there are two main sources of error: stair-casing error due to discretization and numerical dispersion due to calculation of frequency domain dielectric matrix elements with finite number of bases. Sub-cell averaging and harmonic inversion methods are suggested to overcome these errors. For investigation purpose we apply this approach for calculating photonic dispersion of dispersive and non-dispersive photonic crystal slabs. Resulted band structures are verified by conventional FDTD method as well.

A cavity design that combines a "bottom-up" synthesized semiconductor nanowire with a "top-down" fabricated one-dimensional photonic crystal (PhC) has been proposed. In this paper, we present a detailed study of the characteristics of the nanowire-based Bragg mirror and the resulting nanocavities, using finite-difference time-domain (FDTD) code. Based on this proposal, we demonstrate ultra-high Quality factor (Q) on the order of one million, an increase of three orders of magnitude over the Quality factor of an as-grown nanowire. We believe that our design will offer a feasible platform to develop various nanowire-based photonic devices, for example, quantum optical devices that operate in the strong-coupling limit.

We demonstrate a hybrid approach for the realization of novel nanophotonic devices by combining lithographic fabrication techniques with a nano-manipulation method. In particular, we report on the fabrication of photonic crystal cavities as a platform to which arbitrary emitters or other nanoscopic objects can be coupled in a deterministic way by exploiting the manipulation capabilities of an atomic force microscope. In addition, the optical properties of such particle-cavity systems are analyzed with regard to changes of the quality factor and resonance wavelength of the cavity mode. Our approach is well suited to create improved single photon sources and also complex photonic devices with several emitters coupled coherently via shared cavity modes.

In this work, a GaN-based quantum well LED is theoretically analyzed in a multi-layer structure composed of a quantum well embedded in a waveguide core surrounded by photonic crystal slab and a sapphire substrate. The electromagnetic eigenmodes are obtained throughout above structure via revised plane wave-scattering matrix method. The omnidirectional transmission and reflection are investigated for both TE and TM polarizations from diffraction channels in Ewald construction. Then, we introduced angular power density and calculated radiative modes extraction efficiency. All structural parameters, such as lattice geometry, lattice constant, photonic crystal thickness and filling factor, are taken into account. We also investigated the coupling efficiency between waveguide modes and Bloch modes in structure which include decomposed emission and extraction regions. In order to design a quantum well white LED, we used a MQW with adjusted material composition. The photoluminescence spectrum for both TE and TM polarizations is obtained through a combination of k.p perturbation and transfer matrix method.

On-chip micro-interferometers are introduced in which a slab photonic crystal is used as a dispersive material system to enhance the spectral sensitivity. The output interference pattern is observed along a detection plane. The systematic design of these micro-interferometers is discussed. The performance of these devices as on-chip integrated micro-spectrometers is investigated, and it is shown that by properly employing strong dispersive properties of photonic crystals, very compact and high resolution integrated micro-interferometer/spectrometers can be realized for lab-on-a-chip sensing applications.

A charge moving faster than the phase velocity in a medium can produces conical radiation known as Cherenkov radiation. The FDTD numerical technique is used to model this radiation process and the generated light spectrum is used to explore the optical properties of photonic crystal and quasi-crystals. It is shown that the radiation from the fast moving charge is able to provide information on the band gap and transmission spectrums, defect state wavelengths and waveguide propagation.

A multi-layer photonic crystal can be used to suppress coherent thermal conductance below the vacuum conductance value, over the entire high-temperature range. With interlacing layers of silicon and vacuum, heat can only be carried by photons. The thermal conductance of the crystal would then be determined by the photonic band structure. Partial photonic band gaps that present over most of the thermal spectrum, as well as the suppression of evanescent coupling of photons across the vacuum layers at high frequencies, would reduce the amount heat conducting photon channels below that of the vacuum. Thus such multi-layer structures can be very efficient thermal insulators. Besides, the thermal conductance of such structures can exhibit substantial tunability, by merely changing the size of the vacuum spacing.

In the one-dimensional optical analog to Anderson localization, a periodically layered medium has one or more parameters randomly disordered. Such a randomized system can be modeled by an infinite product of 2x2 random transfer matrices with the upper Lyapunov exponent of the matrix product identified as the localization factor (inverse localization length) for the model. The theorem of Furstenberg allows us, at least theoretically, to calculate this upper Lyapunov exponent. In Furstenberg's formula we not only integrate with respect to the probability measure of the random matrices, but also with respect to the invariant probability measure of the direction of the vector propagated by the random matrices. This invariant measure is difficult to find analytically, and, as a result, the most successful approach is to determine the invariant measure numerically. A Monte Carlo simulation which uses accumulated bin counts to track the direction of the propagated vector through a long chain of random matrices does a good job of estimating the invariant probability measure, but with a level of uncertainty. A potentially more accurate numerical technique by Froyland and Aihara obtains the invariant measure as a left eigenvector of a large sparse matrix containing probability values determined by the action of the random matrices on input vectors. We first apply these two techniques to a random Fibonacci sequence whose Lyapunov exponent was determined by Viswanath. We then demonstrate these techniques on a quarter-wave stack model with binary discrete disorder in layer thickness, and compare results to the continuously disordered counterpart.

In terms of operational bandwidth and speed, photonic components are superior to electronic ones. However, it is difficult to control photons on nanoscale structures for data processing and interconnection. Nanophotonic device using surface plasmon (SP) offers an ideal solution to combine the superior technical advantages of both photonics and electronics on the same chip. The SP wavelength is much shorter than that of the exciting light, allowing the use of SP in various techniques that overcome diffraction limits. In this paper, we report an interesting plasmonic effect, enhanced backward scattering, by using a periodically-aligned carbon nanotube (CNT) array. The CNTs are grown on a transparent glass substrate with an average diameter of 50 nm and a length of about 1 μm. To enhance the conductivity, the CNTs are also coated with 10-nm Au layer by using E-beam CVD technique. By shining a laser beam to the CNT array, we found that the scattering intensity is maximally enhanced at the backward incident direction. The enhanced backward incident scattering is observed by using both periodic and nonperiodic CNT samples. The experimental results suggest that the backward scattering effect is due to the SP excitation and coupling. The proposed technique exploiting aligned carbon-nanotube arrays to manipulate surface plasmon will lead to useful optical features such as optical antennae effects, retro-reflection, switching, wavelength add/drop multiplexing, and may be particularly useful for optical sensing, smart target identification and optical wireless secure communication applications.

InGaAsSb narrow gap heterostructures with p-InAsSbP claddings grown onto heavily doped n+-InAs substrates have been processed into 70 μm wide square mesas lined in a 1x4 array with individual addressing of elements. We report I-V, L-I characteristics of the array as well as IR images allowing characterization of cross talk, reflectance of the contacts and apparent temperatures in the spectral range around 3.6 μm. Reflectance and outcoupling efficiency is presented for photonics crystal structures with regard to their implementation in LED assemblies.

We study structural symmetries of two-dimensional (2D) photonic crystals with anisotropic unit cells, including square- and rectangular-lattices with orientationally modulated elliptic motifs, a compound structure consisting of circles with 6-fold rotational symmetry and elliptical lines with 2-fold symmetry, and a rectangular lattice of aligned ovals, which are created through elastic deformation of an elastomeric membrane with circular pores. We then investigate the photonic bandgap (PBG) properties of the corresponding 2D Si posts, and their tolerance to the structural deviation. We find that in the compound structure the overall PBGs are dominated by the sublattice with a higher symmetry, while the total symmetry is determined by the one with a lower symmetry.

We demonstrate that the emission spectrum from a quantum dot near the edge of a photonic band gap (PBG) can be spectrally resolved on the subwavelength scale using coherent control. In the case of the coherent control, confined light near a quantum dot embedded in photonic crystals can be released by changing the phase of the external laser phase, without closing the PBG. Moreover, in this demonstration, we examine the spectrum resolution of the coherent control, which indicates that the spectrum resolution is the subwavelength scale. Therefore, even if there are many quantum dots are embedded in photonic crystals, we can be operated a quantum dot with a specific resonant frequency. This technique may provide a basis for N-qubit operation for quantum computations and nanophotonic devices.