Jitter Correction for Asynchronous Optical Sampling Terahertz Time-Domain Spectroscopy based on Free-Running Pulsed Lasers

Asynchronous optical sampling (ASOPS) on terahertz time-domain spectroscopy (THz-TDS) using two pulsed lasers for pumping and probing THz wave is an excellent sampling method which possesses high frequency resolution and high scan rate without moving mechanics [1]. For a typical setup in ASOPS, the repetition frequencies of lasers must be stabilized strictly to suppress a timing jitter between the THz wave and the probe beam to keep the measurement bandwidth in THz frequency [2]. While a clocking method called adaptive sampling does not require the stabilization, another THz CW laser is necessary to create a special sampling clock which reflect the jitter characteristics [3]. To broaden the range of applications of ASOPS THz-TDS, downsizing the whole system, lowering the cost, removing the technical difficulty, and improving the robustness to environment are highly demanded.