Adaptive sampling dual terahertz comb spectroscopy using free-running dual femtosecond lasers

Dual terahertz (THz) comb spectroscopy is a promising methods for high accuracy, high resolution, and broadband THz spectroscopy because the mode-resolved THz comb spectrum possesses both characteristics of broadband THz radiation and narrow-linewidth continuous-wave THz radiation and all frequency mode of THz comb can be phase-locked to a microwave frequency standard. However, requirement of stabilized dual femtosecond lasers has often hindered wide use of this method. In this article, we demonstrated the adaptive sampling, dual THz comb spectroscopy, enabling use of free-running dual femtosecond lasers. To correct the non-linearity of time and frequency scale caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing signal in a data acquisition board. The demonstrated results did not only indicate the implementation of dual THz comb spectroscopy with free-running dual lasers but also implied the superiority of its spectroscopic performance over the dual THz comb spectroscopy with stabilized dual lasers.