Compact, high-SNR terahertz wave detection using ZnS

Terahertz (THz) waves refer to the segment of the electromagnetic spectrum with frequencies ranging from 0.1 to 10 THz. They are characterized by low photon energy and good biocompatibility. In recent years, the application directions of THz waves have been continuously explored, showing increasingly broad prospects. In the THz field, pump-probe detection is a widely used detection technique that can achieve high time resolution and high signal-to-noise ratio. On the other hand, Yb-doped femtosecond fiber amplifier lasers with wavelengths around 1030nm are emerging in various industrial and scientific applications. Compared with conventional 800nm wavelength Ti:sapphire femtosecond lasers, these systems are more compact and have advantages such as relatively low cost, stability, and ease of maintenance. Therefore, using this type of laser for the generation and detection of THz waves has significant application value. At the same time, we noticed that the group refractive index of ZnS at 515nm (2.78) is relatively close to its refractive index at 1THz (2.87). Therefore, ZnS may be a promising material for THz electro-optic sampling using 515nm wavelength light. In summary, this study uses a 1030nm Yb-doped femtosecond fiber amplifier laser as the THz pump source, and an organic crystal as the generation crystal. The light with a wavelength of 1030nm is converted into light with a wavelength of 515nm as the probe light through a frequency doubling crystal, and ZnS is used as the probe crystal. The pump-probe combined lock-in amplification detection technique is adopted to obtain THz waves with high signal-to-noise ratio.