Research on terahertz transmission characteristics of nonpolar liquid based on frequency-domain spectroscopy

In our research, terahertz frequency-domain spectroscopy based on continuous-wave and coherent detection, which offers advantages of frequency selectivity and much higher frequency resolution, is used to acquire the optical parameter of nonpolar liquid samples in a polytetrafluoroethylene (PTFE) rectangle cell. The transfer matrix method is raised to remove the oscillation generated by the Fabry–Perot interferometer caused by the cell wall; thereby, dielectric constants of liquids can be extracted successfully. The refractive index of the nonpolar liquid samples cyclohexane (C₆H₁₂) and n-Hexane (C₆H₁₄) are obtained within the frequency range of 400–1600 GHz. The processed results of cyclohexane and n-Hexane in our method are basically stable with a refractive index of about 1.42 and 1.37, respectively, which agrees well with the experimental results using other methods previously.