Fabrication of 2-D and 3-D Photonic Band-Gap Crystals in the GHz and THz Regions
Two- and three-dimensiona1 dielectric and metallic structures exhibiting photonic band-gaps in a broad frequency range were fabricated by deep X-ray lithography and laser micro-machining. These techniques seem promising for mass production of photonic structures with full band-gaps in a spectrum ranging from the millimeter wave up to the far infrared regime. Deep X-ray lithography was applied to produce periodic 3-D photonic band-gap structures based on the “three-cylinder” model with mid-gap frequencies up to 2.4 THz. Metallic 3-D structures with incorporated point and linear defects are currently under development. Layered metallic and metallo-dielectric structures exhibiting a cutoff frequency in the microwave regime were fabricated by laser precision machining. The observed cutoff frequency can be easily tuned by varying the interlayer distance or the filling fraction of the metal. Combinations of layers with different metal filling fractions create defect modes with relatively sharp peaks, which are also tunable. The metallo-dielectric structures are significantly smaller than the simple metallic ones. The experimental measurements seem to be in good agreement with theoretical calculations.