Measurement and Research of Liquid Transmission Spectrum Based on Continuous-wave Terahertz Spectroscopy

Terahertz frequency-domain spectroscopy (THZ-TDS) and terahertz time-domain spectroscopy (THz-FDS) are two important methods for the material feature detection in terahertz band. In our research, the terahertz frequency-domain spectroscopy based on the continuous-wave and coherent detection is used to acquire the terahertz spectrum of liquid samples in a customized rectangle cell. The transfer matrix method is used to remove the oscillation generated by the Fabry-Pérot interferometer caused by cell wall, thereby dielectric constants of liquids can be extracted successfully. With the Hilbert transformation to get the amplitude and phase, the high frequency resolution of ~ 14 MHz can be achieved. Then the refractive index of the liquid sample cyclohexane is obtained with the frequency range 0.1-1.7 THz. The results show that our terahertz frequency-domain spectroscopy has high potential for measurement and analysis in the terahertz band.