Coherent injection photocurrent in bismuth sulfide film induced by one-plus-two photon absorption quantum...

Quantum interference (QuI) effect is a powerful method to generate and control the ultrafast photocurrent in semiconductors. We utilize two-color pulsed light excitation in bismuth sulfide (Bi₂S₃) film to induce the photocurrent through the QuI effect. Experimentally, the photocurrent is indirectly monitored using a standard terahertz (THz) time-domain spectroscopic system. Due to the QuI, an asymmetric photon injection occurs in Bi₂S₃ film, resulting in coherent injection current and subsequently THz wave generation. Our results on the pump pulse energy dependence of the THz electric field suggests that the THz wave generation process follows the third-order nonlinear optical process.