A simple method to find temporal overlap between THz and x-ray pulses using x-ray-induced carrier dynamics in semiconductors

Abstract

X-ray-induced carrier dynamics in silicon and gallium arsenide were investigated through intensity variations of transmitted terahertz (THz) pulses in the pico- to microsecond timescale with x-ray free-electron laser and synchrotron radiation. We observed a steep reduction in THz transmission with a picosecond scale due to the x-ray-induced carrier generation, followed by a recovery on a nano- to microsecond scale caused by the recombination of carriers. The rapid response in the former process is applicable to a direct determination of temporal overlap between THz and x-ray pulses for THz pump–x-ray probe experiments with an accuracy of a few picoseconds.