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

Takeshi Yasui,

Ryuji Ichikawa,

Yi-Da Hsieh,

Kenta Hayashi,

Harsono Cahyadi,

Francis Hindle,

Yoshiyuki Sakaguchi,

Tetsuo Iwata,

Yasuhiro Mizutani,

Hirotsugu Yamamoto,

Kaoru Minoshima

& Hajime Inaba

http://www.nature.com/srep/2015/150602/srep10786/full/srep10786.html

Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales 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 clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers.