Robust asynchronous optical sampling terahertz spectroscopy using commercially available free-running lasers

This study presents the utilization of asynchronous optical sampling (ASOPS) terahertz spectroscopy with commercially available Ti:Sapphire lasers, eliminating the need to stabilize the repetition frequency. Our postprocessing algorithm, which utilizes the multiplied repetition frequency difference as a calibration signal, effectively corrected the jitter, enabling broadband (2.5 THz) spectroscopy with a high spectral resolution (82 MHz). The robustness of the jitter correction based on the free-running laser setup and broadband electric circuits was rigorously examined under varying temperatures, thereby demonstrating reliable long-term operations over 63 h. This study broadens the applicability of ASOPS terahertz time-domain spectroscopy.