Characterization of photonic crystals at microwave frequencies

Abstract

VVe investigated the surface reflection properties of layer-by-layer photonic crystals, for dielectric and metallic based photonic crystals. By using a FabryPerot cavity analogy with the reflection-phase information of the photonic crystals, we predicted defect frequencies of planar defect structures. Our predictions were in good agreement with the measured defect frequencies. The Fabry-Perot cavity analogy was also used to relate the quality factors of the planar defect structures to the transmission of the mirrors of the cavity. A simple model was used to simulate the transmission spectra of planar defect structures, which agreed well with the experimental data. We also investigated the transmission and reflection properties of two different metallic crystal structures (face-centeredtetragonal and simple tetragonal). We obtained rejection rates of 7-8 dB per layer from metallic crystals. Defect modes created by removing rods resulted in high peak transmission (80%), and high quality factors (1740). Our measurements were in good agreement with theoretical simulations of metallic structures. Planar defect structures built around metallic structures resulted in higher quality factors (2250). We observed high reflection-rejection ratios (-80 dB) at defect frequencies for planar defect structures, which was explained by using the Fabry-Perot analogy. Finally, the enhanced field inside the defect volume was measured, by using a monopole receiver antenna inserted inside the defect. The maximum observed enhancement with respect to the incident field was around 200 for a planar defect structure. By placing a Schottky diode detector inside planar and box-like defects, we built resonant cavity enhanced (RCE) detectors and measured the enhanced field inside the defect.