Effects of electric field screening induced by photogenerated carriers on terahertz wave measurement in a GaAs epitaxial structure

Abstract In this work we investigate the effects of electric field screening induced by photogenerated carriers on terahertz wave radiation originating from transient phenomena in the electric field region of a GaAs epitaxial structure. The transient-phenomena excitation and timing of the screening are individually controlled by a pair of ultrashort optical pulses separated by a time interval. Under the condition that the preceding pulse is intensity-modulated by an optical chopper and is irradiated to the sample, the amplitude of the terahertz wave generated by the subsequent pulse is modulated. This result originates from electric field modulation by photogenerated carriers in the preceding pulse.