Design of isotropic photonic gaps by using a circular photonic crystal

摘要

Optical characteristics of a circular photonic crystal (CPC) in the frequency range of 0 to 20 GHz were investigated. The sample was made by alumina rods of 2 mm in radius and 300 mm in length. The alumina rods were arrayed in the form of concentric circles with 6-fold symmetry. The transmission spectra were calculated at various radical distances. When the radical distance was 8 mm, a photonicgap was obtained around 12 GHz. The experimental results were in good agreement with the calculations. Although the lattice positions were shifted from the ones of the CPC, the same transmission spectrum was obtained in the phase-shifted CPC. Phase-shift is a useful means for eliminating translational symmetries that would often appear in the exterior part of a CPC composed of numerous concentric circles. Isotropic photonicgaps were obtained for both a CPC and the phase-shifted CPC.