Laser-machined layer-by-layer metallic photonic band-gap structures

Metallic photonic band-gap crystals operating in the microwave frequency ra nge were fabricated by laser precision machining. They consist of stainless steel plates with a tetragonal lattice of holes and a lattice constant of 15 mm. Transmission measurements show that periodic crystals exhibit a cuto ff frequency in the 8-18 GHz range, below which no propagation is allowed. The cutoff frequency can be easily tuned by varying the interlayer distance or the filling fraction of the metal. Combinations of plates with differen t hole diameters create defect modes with relatively sharp peaks, which are tunable. The experimental measurements are in good agreement with theoreti cal calculations. (C) 1999 American Institute of Physics. [S0003-6951(99)03 822-X].