Design of a highly efficient photoconductive terahertz modulator enhanced by photonic crystal resonant cavity

We present an optically-controlled terahertz (THz) intensity modulator based on photocarrier modulation of GaAs semiconductor, incorporated with photonic crystal cavity-waveguide coupling structure. Here, we demonstrate the intensity of the THz wave can be tuned by varying the conductivity of the GaAs through an infrared optical pumping. Employing the photonic crystal cavity allows for trapping the THz wave within the cavity and strong interaction with photoconductive material occurs. Thus only a weak optical power is required to achieve a deep modulation efficiency with GHz rate. Simulation results indicate with an external optical power of 90 mW, a high modulation rate up to 3 GHz with a modulation depth of more than 94% is achieved for 1 THz carrier wave.