Tunable Terahertz Amplifier Based on Slow Light Edge Mode in Graphene Plasmonic Crystal

A terahertz (THz) amplifier based on graphene plasmonic crystal is presented in this paper. The amplifier is composed of periodic graphene-silicon arrays, and graphene is used as the THz wave gain medium due to its negative conductivity at a certain temperature and bias voltage. The plasmonic bandgap and cascade amplification effect effectively improve the gain of the THz wave in a single slow light mode at the photonic band edge, which greatly increase the effective interaction distance of THz waves in the graphene with a limited gain coefficient and gain medium thickness. Moreover, with the thermal and electronic control on the conductivity and refractive index of graphene, the operating frequency and amplification efficiency of this device can be broadly tuned. The results show that a THz output with a gain of larger than 30 dB and Q value of 720 is achieved in this device. This device has a great potential application in the THz communication, imaging, and radar system integrated with other THz solid-state electronic sources and detectors.