META Conference, META'10

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Microwave Frequency Selection by Active Plasma Photonic Crystal
Max Chung, Shiaw Hwei Chen

Last modified: 2009-11-06


Various photonic crystal structures have been reported before, with fixed band gaps which are functions of its geometry in three dimensions. Here a photonic crystal composed of DC plasma column is tested, and frequency selectivity in microwave range is achieved. Plasma is a dispersive medium, and its reflective index is a function of electron density and temperature, which are controllable via adjustments in input power. When stands along, plasma acts as a high pass filter. If the incoming frequency is lower than the characteristic plasma frequency ωpe, the plasma behaves as metal with a transition frequency range that could be wide at instances. If the incoming frequency is higher than the characteristic plasma frequency ωpe, it behaves as an attenuating dielectric. When many of these plasma columns are arranged in periodic structure, the property of photonic crystal is combined with the plasma and form a controllable band pass filter. A two dimensional photonic crystal structure is created using plasma column of 12 mm diameter filled with low temperature low pressure discharge gas. When turned on, multiple enhanced and forbidden band transmission measurement appears. Enhancements as high as 10 dB and attenuations as low as -20dB are observed. When turned off, the region is back to dielectric reflection only. This device can be applied in radar.