A terahertz photonic crystal cavity with high Q-factors

A terahertz 1D photonic crystal cavity with very high Q-factor is demonstrated. The cavity consists of two parallel distributed Bragg mirrors and one air layer between them as defect layer. By increasing the length of the defect layer, the cavity has a very narrow transmission bandwidth of 30 MHz at resonant frequency of 336 GHz, i.e., a high Q over 1.1 × 10⁴ is achieved. Furthermore, an optically controllable THz switch is demonstrated by light irradiating on one of the middle silicon wafer in the cavity. And the power of optical beam needed for the switch is remarkably reduced to 0.16 W/cm², which is nearly 50 times smaller than that for a THz switch using a single silicon wafer.