Active control of plasmon-induced transparency based on a GaAs/Si heterojunction in the terahertz range

Active control optical terahertz modulator based on incorporating n-type GaAs film as the active media into plasmon-induced transparency metasurface, was investigated theoretically and experimentally. From the experimental results it could be found that the resonances transmission of the plasmon-induced transparency was optically modulated and the transmission modulation depth of 87% was achieved at 0.56 THz. This may be due to the fact that when the pump excitation power was tuned from 0 mW to 1000 mW, larger numbers of excited carriers were excited in the electronic "p-n" junction and diffused across the heterojunction to the n-type GaAs film. It increased the conductivity of the n-type GaAs film from 2.29 x 10(3) S/m to 1.56 x 10(4) S/m. As a results, the capacitive split gaps of the PIT split-ring resonators were short-circuited and the coupling strength between the resonators was decreased owing to the screening effect caused by the photo-excited carriers.