Ultrafast nonlinear travel of hot carriers driven by high-field terahertz pulse

We aim to generate high-intensity terahertz (THz) electric fields and study nonlinear phenomena in GaAs and graphene to investigate their applications. To obtain a high-efficiency intense THz field, we employ the tilted pump-pulse front technique using a LiNbO₃ crystal. With this technique, we obtain a THz field strength of over 300 kV cm^-1. We investigate the hot-carrier dynamics in n- and p-type GaAs driven by high-field THz pulses. Although both samples show similar carrier concentrations, the nonlinear THz responses show different trends. Owing to hot-carrier generation, intervalley scattering is dominant in n-type GaAs, and intervalence band scattering is the main cause in p-type GaAs. In addition, we study the hot-carrier dynamics in graphene with the grain-size dependency. Although graphene has the same Fermi level regardless of the grain size, the THz responses are different for large- and small-grained graphene: charged impurity scattering in large-grained graphene and defect scattering in small-grained graphene. From these results, our study provides insights into high-speed electronics applications.