Huang Y, Sun P, Zhang Z, Jin C
Appl Opt. 2017 Jul 10;56(20):5698-5704. doi: 10.1364/AO.56.005698.
Water vapor noise in the air affects the accuracy of optical parameters extracted from terahertz (THz) time-domain spectroscopy. In this paper, a numerical method was proposed to eliminate water vapor noise from the THz spectra. According to the Van Vleck-Weisskopf function and the linear absorption spectrum of water molecules in the HITRAN database, we simulated the water vapor absorption spectrum and real refractive index spectrum with a particular line width. The continuum effect of water vapor molecules was also considered. Theoretical transfer function of a different humidity was constructed through the theoretical calculation of the water vapor absorption coefficient and the real refractive index. The THz signal of the Lacidipine sample containing water vapor background noise in the continuous frequency domain of 0.5-1.8 THz was denoised by use of the method. The results show that the optical parameters extracted from the denoised signal are closer to the optical parameters in the dry nitrogen environment.
空气中的水蒸气噪声会影响从太赫兹（THz）时域光谱中提取的光学参数的准确性。本文提出了一种数值方法来消除太赫兹光谱中的水蒸气噪声。根据范弗莱克 - 魏斯科普夫函数以及HITRAN数据库中水分子的线性吸收光谱，我们模拟了具有特定线宽的水蒸气吸收光谱和实折射率光谱。同时也考虑了水蒸气分子的连续效应。通过对水蒸气吸收系数和实折射率的理论计算，构建了不同湿度下的理论传递函数。利用该方法对在0.5 - 1.8 THz连续频域内含有水蒸气背景噪声的拉西地平样品的太赫兹信号进行了去噪处理。结果表明，从去噪后的信号中提取的光学参数更接近干燥氮气环境中的光学参数。
