Metallic tunable photonic crystal filter for terahertz frequencies

A tunable metallic photonic crystal filter has been fabricated by deep reactive ion etching of a silicon substrate followed by metallization. The filter plate's two-layer orthogonal grid structure and integrated mounting lugs were fabricated from a single silicon wafer in two etching steps. A three-step metallization process (evaporation, sputtering, and electroplating) ensured all surfaces were coated with gold to greater than 4.6 times the skin depth at the frequencies of interest. The filter employs. a mechanical tuning mechanism, the performance of which was predicted with rigorous full-vector electromagnetic simulations (finite-difference time domain). The prototype has been characterized at frequencies of 70-150 GHz using free-space measurement techniques. Its measured center frequency shifts from 144 to 137 GHz for 300 mum lateral shift of one of the plates, and it has an insertion loss of less than I dB. (C) 2003 American Vacuum Society.