Periodic dielectric and metallic structures have recently generated great interest because they can exhibit a forbidden range of frequency, or a photonic band gap (PBG) where the electromagnetic waves cannot propagate. Since their theoretical prediction in 1987, several applications at frequencies ranging from microwave to optical region have been proposed using these novel structures. This presentation demonstrates the first successful fabrication of flexible metallic PBG structures that show frequency filtering properties at far-infrared frequencies;The metallic PBG filters described here are multi-layered metallic meshes imbedded in a flexible polyimide dielectric. They have a simple, microfabrication-based construction that use alternating dielectric and metal layers and result in structures that are mechanically flexible. Depending on the periodic pattern of the metal grids, the filters have either simple high-pass, band stop or a more complex transmission characteristic. The critical frequencies of the filters depend on the spatial periodicity of the metal grids and the inter-layer separation. The transmission characteristic of these filters show cut-off frequencies in the far-infrared region with very high attenuation (\u3e35 dB) and large fractional bandwidths;The measured values are in very good agreement with theoretical results. The filters maintain their optical characteristics after repeated bending, demonstrating mechanical robustness of the metallic PBG structure. Rapid cooling of the samples in liquid nitrogen also does not show any visible stress on the sample or its optical characteristics making them excellent candidates for space applications.
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