Extraction of beat signal between dual THz combs using dual THz spectrum analyzers

It is crucial in asynchronous-optical-sampling THz time-domain spectroscopy or dual THz comb spectroscopy to suppress the timing jitter of the mode-locked frequency between two femtosecond lasers or frequency fluctuation of a beat signal between two THz combs because the fluctuation of them distorts the linearity of frequency scale in the spectrum. In this paper, dual THz spectrum analyzers were effectively used to extract a beat signal between dual THz combs around 0.1 THz. The resulting beat signal has a linewidth below 1Hz and a signal-to-noise ratio of 20 dB. Furthermore, the extracted beat signal was used to suppress the remained timing jitter effectively.