Pump-power dependence of THz radiation from InAs surfaces under magnetic fields excited by ultrashort laser pulses

THz radiation from InAs surfaces excited by ultrashort laser pulses has bee n studied under low (similar to0.6 muJ/cm(2) fluence) and high (similar to6 mJ/cm(2) fluence) pump power densities. The THz radiation amplitude is aff ected in both cases. We found that the radiation wave form is broadened by applying magnetic fields for the low-density-excitation case whereas it is not for the high-density-excitation case. This result is explained by the d ifference of the effect of the magnetic field on the THz radiation due to t he transient photocurrent and optical rectification effects. (C) 2001 Ameri can Institute of Physics.