Characterization of a Three-Dimensional Microwave Photonic Band-Gap Crystal

Abstract

A microwave photonic crystal has been constructed and characterized experimentally and computationally. The material has prominent electromagnetic features characteristic of a three-dimensional photonic band structure material. Measurements of transmission coefficients show that the material has a first band-gap (i. e., a frequency gap where extended modes are forbidden) between 10.9–13.1 GHz. The damping of transmitted amplitude is typically −40 dB in this band-gap, and close to 0 dB (with dips due to interference effects reaching down to −8 dB) within the bands (i. e., at frequencies where extended modes are allowed). Calculated transmission spectra agree qualitatively with measurements, and discrepancies are explained in terms of approximations made in the computational model. The time average Poynting vector (flow of electromagnetic power), has been calculated on a plane cut, parallell to the direction of incidence, through a model of the photonic crystal. The Poynting vector is strongly reduced at 9–12 GHz. This region corresponds well to the first band-gap. It is contemplated how a three-dimensional photonic band structure material could be utilized in radar signature managements applications.