Frequency up-shift of THz light via relativistic Doppler reflection: As new probe for investigating carrier dynamics

Abstract

We have applied the terahertz (THz) time-domain spectroscopy (TDS) to revealing the mechanism of the relativistic Doppler reflection of the THz light from a photo-induced plasma layer in a silicon wafer. The velocity of moving plasma layer is estimated by the reflected THz waveforms as a function of pump and probe delay time. We found that the interaction time of the moving plasma front and the reflected THz pulse is a key factor to understand the mechanism of the relativistic Doppler reflection and modified the up-shift factor.