Characteristics of resonant modes of photonic crystal cavities

Abstract

We investigate the characteristics of resonant mode of a cavity with two-dimensional (2D) photonic crystal (PC) mirrors using the finite difference time domain simulation. The employed PC mirrors are composed of a square array of dielectric rods in air. As the dielectric constant of the rods increases, the frequency of resonant mode decreases whereas its Q factor increases. However, both the frequency and Q factor of a resonant mode increases as the number of dielectric rod increases. To clarify the mechanism that determines the frequency of resonant modes, we have studied the characteristics of resonant modes of one-dimensional PC cavities made of PCs. Our study of one-dimensional PC cavity demonstrates that both the phase change due to the reflection at the surface of PC mirror and the optical path length between PC mirrors play important roles in the determination of the position of resonant frequency. We also discuss the tunable PC filters implemented with the PC mirrors composed of some materials, such as liquid crystal, whose dielectric constant depends on an external field. In this case, the phase change due to the reflection can be controlled by changing the dielectric constant of liquid crystals in the PC mirrors.