Femtosecond Optical Pump Induced Enhancement of Terahertz Radiation from GaAs Surface

Terahertz (THz) far infrared radiation with a subpicosecond pulse duration is generated from GaAs(100) surface illuminated by femtosecond laser pulses. By illuminating the sample with another pump pulse, we observe an enhancement of THz emission. A mechanism of photocarriers trapping by impurities and defects in the depletion layer is proposed.