Two-Color-Driven Controllable Terahertz Generation in ITO Thin Film

Seeking new compact and controllable terahertz sources has garnered enormous interest across various disciplines. In our recent preliminary work, we have showcased the potential of an ultrathin indium tin oxide (ITO) film as an innovative platform for generating broadband terahertz waves. In this study, we conducted both experimental and theoretical investigations into a two-color femtosecond-laser-driven broadband terahertz generation in an ITO thin film. By adjusting the time delay and polarizations of the two driving pulses, we observed that the broadband terahertz waves exhibited nearly 100% amplitude modulation and 360° polarization angle tuning. To interpret the controllable processes, we employed a degenerated four-wave mixing (FWM) model. Our results indicated a correlation between the two-color interaction process and the second-order optical rectification process at the ITO film's surface, which either enhanced or suppressed the overall terahertz generation.