Excitation fluence dependence of terahertz radiation mechanism from femtosecond-laser-irradiated InAs under magnetic field

The excitation fluence and magnetic field dependence of terahertz (THz) radiation power from InAs is investigated. At low excitation fluence, an enhancement of the THz-radiation power is observed independent of the magnetic-field direction. As the excitation fluence is increased, a crossover of the terahertz radiation mechanism is observed. At excitation fluence above this crossover, the radiation power is either enhanced or reduced depending on the magnetic-field direction. These results are explained by considering the different THz-radiation mechanisms from the InAs surface with or without photoexcited carrier screening.