Development of fast scan THz-TDS system by using repetition rate tunable femtosecond laser

In order to completely prevent the mixture of different medicines and also their contamination by foreign objects it is necessary to inspect all medicines in the manufacturing process. In line with this, THz time-domain spectroscopy (THz-TDS) is considered to be a promising technique applicable to the quality-control inspection system along the production line of chemicals and medicinal tablets. However, previous THz-TDS utilizes mechanical type time-delay scanning stage that requires several minutes in order to acquire a THz time waveform. Therefore, it is difficult to introduce this THz-TDS into the system. In the present study, we aim to develop a method for high-speed sampling of the THz waveform to significantly shorten the measurement time in the THz-TDS by changing the repetition rate of the femtosecond laser. The high-speed sampling method proposed was applied to a THz-TDS and the proof of principal experiment was done.