タイムストレッチ法を用いた高繰り返し超高速分光法とその応用

抄録

High-repetition-rate ultrafast pump-probe and terahertz spectroscopies were achieved by combining time-stretching and time-encoding techniques. We used chirped probe pulses to map the temporal information to the spectrum and observed its pump-induced change using a combination of a chirped fiber Bragg grating and a photodiode. The repetition rate of the waveform acquisition is as high as 75 kHz, which is limited by the repetition rate of the excitation laser. We applied the method to the observation of ultrafast dynamics in the formation of laser-induced periodic surface structures (LIPSS) and laser ablation in a phase change material, Ge2Sb2Te5 thin film. The observed pulse-to-pulse change of the ultrafast dynamics during LIPSS formation reveals the importance of ultrafast processes for energy relaxation, demonstrating promising capability of our proposed method.