I will survey theoretical calculations and experimental measurements on colloidal photonic crystals synthesized at iowa State university. These crystals show reflectivity peaks at optical wavelengths. Optical mesurements on these photonic crystals indicate a geometry that is considerably distorted from ideal. band structure calculations of the positions of the stop bands will be utilized to determine the structure of the crystal and refractive index of the background material. the dependence of photonic properties with stacking and disorder will also be discussed. Alternative photonic lattices with photonic gaps will be discussed. (In collaboration with G. Subramania, K. Constant, M. M. Sigalas, K.-M. Ho, and C. M. Soukoulis) Supported by the U.S. Dept. of Energy/Office ofo basic Energy Sciences.
Three-dimensional photonic band gap crystals are utilized to tailor the
radiation patterns of antennas. By utilizing the resonances of a Fabry Perot
cavity formed with photonic band gap crystals, we were able to create uniquely
directional antennas by placing antennas within such cavity. Very good agreeement
was obtained between finite difference time domain (FDTD) simulations and
measurements[1]. Exceptionally directional patterns over narrow frequency
ranges were obtained, with half power beam widths less than 10 degrees were
obtained. We will compare the theoretical performance of 3-D and 1-D photonic crystals.
These recent results will be compared with past configurations where dipole antennas
were placed on top of photonic crystals and the reflecting properties of the
PBG crystals were used to improve antenna performance. Such directional
promise several new applications.
[1] B. Temelkuran et al., J. Appl. Phys. 87, 603 (2000)
*Supported by the U.S. Department of Energy