Fine Tuning of Single Row Photonic Crystal Extended Cavities Embedded in Photonic Wire Waveguides

摘要

This paper describes the realization of high quality factor (Q-factor) single row photonic crystal extended cavity structures embedded in 500 nm wide photonic wire waveguides. Cavities spacer lengths of between 2 μm and 9 μm have been inserted between two periodic mirrors with aperiodic tapering of the hole diameter and the spacing between holes. A Q-factor value of approximately 74,000 has been measured for a 5 μm long cavity at a selected resonance frequency. We have also demonstrated experimentally a tuning capability for the resonance frequency by means of small variations of the cavity length. A shift of approximately 10 nm in resonance frequency has been obtained for a 250 nm variation of the cavity length, both in simulation and in measured results. In addition, a free spectral range (FSR) in resonance frequency of between 20 nm and 30 nm has also been demonstrated for a small variation in the mirror hole diameter of approximately 20 nm. Tapering within and outside the cavity has produced a substantial increase in both the Q-factor and the optical transmission at resonance. Both 2D and 3D finite-difference time-domain (FDTD) computations have been used to simulate the device structures. Comparisons between the simulation and measured results show reasonably good agreement.