Mode Characteristics for Square Resonators With a Metal Confinement Layer

Microsquare resonators laterally confined by SiO₂/Au/air multilayer structure are investigated by light ray method with reflection phase-shift of the multiple layers and two-dimensional (2-D) finite-difference time-domain (FDTD) technique. The reflectivity and phase shift of the mode light ray on the sides of the square resonator with the semiconductor/SiO₂/Au/air multilayer structure are calculated for TE and TM modes by transfer matrix method. Based on the reflection phase shift and the reflectivity, the mode wavelength and Q factor are calculated by the resonant condition and the mirror loss, which are in agreement well with that obtained by the FDTD simulation. We find that the mode Q factor increases greatly with the increase of the SiO₂ layer thickness d , especially as d < 0.3 ¿m . For the square resonator with side length 2 ¿m and refractive index 3.2, anticrossing mode couplings are found for confined TE modes at wavelength about 1.6 ¿m at d = 0.11 ¿m, and confined TM modes at d = 0.71 ¿m, respectively.