Terahertz-pulse-induced hot-electron transport in photoexcited GaAs

We observe self-induced absorption bleaching of intense terahertz (THz) pulses in photoexcited GaAs using optical-pump/THz-probe techniques. The sample is excited using 800nm, 50fs laser pulses and probed collinearly using few-cycle THz pulses with energies up to 0.6$\mu $J. The relative transmission of the THz probe pulse through the photoexcited GaAs increase at high probe fields. A simple dynamic electron transport model demonstrates that the nonlinear response arises from a decrease in electron conductivity due to intervalley electron scattering induced by the THz electric field over sub-picosecond time scales as well as an increase in the intravalley scattering rate.