Terahertz time-domain spectrum technology is a far infrared coherent spectral measurement technology developed by D. H. Auston etc. on basis of antenna radiation mechanism in 1980s'. This technology respectively records terahertz time-domain electric field waveforms when there is a sample or not by terahertz radiation pulse passing through the sample or being reflected by the surface of the sample. Signals' frequency-domain waveforms, when there is a sample or not, are obtained from these two waveforms by means of fast Fourier transform. The detected sample's refractive index, dielectric constant, and absorption coefficient can be obtained by executing related mathematical calculation processing on the frequency-domain data. Compared with traditional spectroscopy technologies, the terahertz time-domain spectroscopy technology not only has broader measurement bandwidth, higher spectral resolution, and better spectral signal-to-noise ratio, but also can record the amplitude information and the phase information of the detected sample signal at the same time.
A typical terahertz time-domain spectrometer system comprises a femtosecond pulse laser, a terahertz radiation device, a terahertz detection device, and a delay line device. A traditional delay line device is generally based on a stepping motor to build a set of symmetrical reflectors to achieve optical path's 180-degree reversal, and then the delay adjustment of a pump light path and a probe light path is implemented by a motor controller. However, this device has the inherent defects of heavy, large area occupation, and no modular integration, so that it is not suitable for the terahertz time-domain spectrometer system with the characteristics of commercialization, miniaturization, and portable.