Resonant modes in continuous metallic grids over ground and related spatial-filtering applications

Abstract

We use the theory of periodic structures, full-wave electromagnetic, and microwave circuit simulations to explain the resonant modes that propagate in metallic grids having rectangular unit cells constructed over a ground plane. We show that these metallic grids can support two types of resonant modes that have rectangular and hyperbolic isofrequency dispersion contours. By exploiting the spatial dispersion properties of these modes, a microwave 3GHz∕6GHz harmonic splitter and a highly selective 5.8GHz∕6.2GHz diplexer are designed and simulated. Furthermore, we provide experimental results for the diplexer and for the harmonic splitter, synthesized in microstrip technology. The proposed metallic grids utilize continuous unloaded transmission-line segments thus leading to spatial-filtering devices that are easy to fabricate and are scalable to terahertz frequencies and beyond.

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

“…Simultaneous spatial and frequency domain filtering is required for controlling laser radiation. 3 The known implementations of spatial filters include anisotropic media, 1 resonant grating systems, 3,4 interference patterns, 5 multilayer stacks combined with a prism, 2 metallic grids over a ground plane, 6 and slabs of photonic crystal ͑PC͒ with defects. 7 The possibilities for the realization of narrow bandpass filters 3,4,7 and low-pass, high-pass, and wide bandpass filters with a rather steep switching between pass-and stopbands 1,2 have been demonstrated.…”

Femtosecond direct laser writing of photonic spatial filters in soda–lime glass

“…Such a configuration extends over at least two focal lengths of both lenses and is of a relatively large size -it could hardly be used in micro-or nano-scale photonic devices. Other, more sophisticated arrangements for spatial filtering based on liquid-crystal cells [2], utilization of thin film interfaces [3], anisotropic media [4], metallic grids [5], possibly including monolithically integrated passive beam shaping elements [6], etc. have not resulted in widespread technological applications.…”

Spatial filtering using dielectric photonic crystals at beam-type excitation

“…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.…”