M. M. Sigalas

Photonic band gaps in three dimensions: New layer-by-layer periodic structures

Abstract A new three-dimensional (3D) periodic dielectric structure constructed with layers of dielectric rods of circular, elliptical, or rectangular shape is introduced. This new structure possesses a full photonic band gap of appreciable frequency width. At midgap, an attenuation of 21 dB per unit cell is obtained. This gap remains open for refractive indices n ≥ 1.9. Furthermore, this new 3D layer structure potentially has the additional advantage that it can be easily fabricated using conventional microfabrication techniques on the scale of optical wavelengths.

Elastic and acoustic wave band structure

A periodic structures consisting of identical spheres placed periodically within a host homogeneous material is here investigated.

Ultracompact biochemical sensor built with two-dimensional photonic crystal microcavity

By measuring the resonant wavelength of a two-dimensional photonic crystal microcavity, we can detect the change in refractive index of 0.002. Evaporative process of water in 5% glycerol is used to demonstrate time-resolved sensing capability

InGaN/GaN quantum-well heterostructure light-emitting diodes employing photonic crystal structures

Electrical operation of InGaN/GaN quantum-well heterostructure photonic crystal light-emitting diodes (PXLEDs) is demonstrated. A triangular lattice photonic crystal is formed by dry etching into the top GaN layer. Light absorption from the metal contact is minimized because the top GaN layers are engineered to provide lateral current spreading, allowing carrier recombination proximal to the photonic crystal yet displaced from the metal contact. The chosen lattice spacing for the photonic crystal causes Bragg scattering of guided modes out of the LED, increasing the extraction efficiency. The far-field radiation patterns of the PXLEDs are heavily modified and display increased radiance, up to ∼1.5 times brighter compared to similar LEDs without the photonic crystal.

Micromachined millimeter-wave photonic band-gap crystals

We have developed a new technique for fabricating three‐dimensional photonic band‐gap crystals. Our method utilizes an orderly stacking of micromachined (110) silicon wafers to build the periodic structure. A structure with a full three‐dimensional photonic band gap centered near 100 GHz was measured, with experimental results in good agreement with theoretical predictions. This basic approach described should be extendable to build structures with photonic band‐gap frequencies ranging from 30 GHz to 3 THz.

Photonic crystal-based resonant antenna with a very high directivity

We investigate the radiation properties of an antenna that was formed by a hybrid combination of a monopole radiation source and a cavity built around a dielectric layer-by-layer three-dimensional photonic crystal. We measured a maximum directivity of 310, and a power enhancement of 180 at the resonant frequency of the cavity. We observed that the antenna has a narrow bandwidth determined by the cavity, where the resonant frequency can be tuned within the band gap of the photonic crystal. The measured radiation patterns agree well with our theoretical results.

Classical vibrational modes in phononic lattices: theory and experiment

Abstract We present a review, through selected illustrative examples, of the physics of classical vibrational modes in phononic lattices, which elaborates on the theory, the formalism, the methods, and mainly on the numerical and experimental results related to phononic crystals. Most of the topics addressed here, are written in a self-consistent way and they can be read as independent individual parts.

Tight-Binding Parametrization for Photonic Band Gap Materials

ever, there exist two important differences. First, Mie resonances’ states are not localized; in fact, they decay too slowly, as 1yr as r ! ‘, and this may lead to divergences in some matrix elements. However, in a lattice environment they may be taken as localized, with a localization length comparable to the interparticle dimension. Second, in the classical wave case, as opposed to the electronic case, the host medium supports propagating solutions for every frequency. For large wavelengths, this is the dominant propagation mode since no resonances have been excited yet, while for wavelengths comparable to the particle dimension, transmission is achieved mainly through transfer between neighboring localized resonances. Thus, we may assume that the lowest frequency band is plane wavelike, while the higher bands are TB-like. This picture is more easily justified in the case of wide gaps and narrow bands, but its validity seems to be much wider. Within the framework of the systems we studied, we verified this picture. Furthermore, we were able to show that the TB matrix elements, after an appropriate rescaling, are functions of the distance only. We will consider the scalar case of a 2D periodic array of N infinitely long dielectric cylinders in vacuum, with periodic boundary conditions and with the incident plane wave E polarized. We assume the normalized electric field for each band to be given by Ens

Theoretical study of three dimensional elastic band gaps with the finite-difference time-domain method

Photonic crystals of close-packed arrays of air spheres in a dielectric background of titania have been fabricated with a ceramic technique. Unlike previous methods, ordering of the spheres and the formation of the titania network are performed simultaneously. The photonic crystals exhibit a reflectance peak and a uniform color at the position of the first stop band. The wavelength of the reflectance peak scales very well with the sphere size.