Toward photonic crystal based spatial filters with wide angle ranges of total transmission

Abstract

Spatial filters with steep switching between wide ranges of total transmission and total reflection can be obtained by using two-dimensional dielectric photonic crystals, which are a few wavelengths thick. The guidelines for engineering bandpass and bandstop filters are given. The flatness of isofrequency contours that are localized around a periphery point of the first Brillouin zone is a necessary but insufficient condition for the existence of wide angle ranges of total transmission at intermediate and large angles of incidence. Such ranges that are wider than 20° are demonstrated. © 2009 American Institute of Physics

Spatial filtering using dielectric photonic crystals at beam-type excitation

“…The selected parameters are quite close to those in Ref. 7. Accordingly, the basic dispersion and plane-wave transmission characteristics are expected to be similar to those in Figs.…”

“…7 Then, the dualbandpass and bandstop regimes corresponding to these distinct frequency values are easily spotted in Fig. 1.…”

“…12 In the present paper, we numerically and experimentally examine the spatial filtering mechanism which is proposed in Ref. 7. However, the present study focuses on the realization of a PC based spatial filter operating under a beam-type excitation, instead of a hypothetical plane-wave illumination.…”

“…In particular, they were employed in the analysis of the spatial spectrum, the enhancement of the antenna directivity, radar data processing, aerial imaging, and distinguishing the incoming radiations with respect to the source location. The known theoretical and experimental implementations of the spatial filters involve those based on anisotropic media, 1 multilayer stacks that are combined with a prism, 2 resonant grating systems, 3 interference patterns, 4 metallic grids over a ground plane, 5 two-dimensional ͑2D͒ photonic crystals ͑PCs͒ with 6 and without 7 defects, chirped PCs, 8 as well as one-dimensional piecewise-homogeneous PCs 9 and graded-index PCs. 10 The coexisting spatial and frequency domain filtering has been studied in the context of controlling the laser radiation with the aid of the resonant grating based filters.…”

“…In order to overcome these difficulties, an approach has recently been offered for the plane-wave excitation, 7 which is based on the use of the 2D dielectric PCs possessing nearly-flat isofrequency contours ͑IFCs͒ and yielding firstorder diffraction for large . In the case of a square-lattice PC, IFCs that are localized around M point of the irreducible Brillouin zone are required for obtaining a bandpass spatial filter, whereas IFCs that are located simultaneously near ⌫ and M points are needed for a bandstop spatial filter, at least if sgn = const.…”