一种利用透射式太赫兹时域光谱技术精确提取样品折射率的方法

运用透射式太赫兹时域光谱技术提取可区分回波样品折射率,主要依靠测得信号的相位差计算得到.具体有两种方法:一是利用参考脉冲和太赫兹波第一次透过样品的脉冲信号,二是利用太赫兹波第一次透过样品的脉冲信号和经样品内部反射两次后的第二个透射信号.实际操作中入射光束与样品表面法线存在夹角,该夹角不易测量,计算时通常忽略,这会最终引起折射率的测量误差,且该误差与选用的折射率提取方法有关.在分析两种方法因夹角引起误差的基础上,提出一种全新的折射率修正方法,该方法能从理论上消除夹角引起的误差,同时实验验证了该方法的有效性.

Extraction of refractive indices of materials through transmission terahertz time-domain spectroscopy

For samples with distinguishable echoes in detected transmission pulses, we mainly use the phase difference between the detected pulses to extract their refraction indices by transmission terahertz time-domain spectroscopy. Specifically, there are two methods. The first one requires the reference pulse and the first terahertz pulse transmitted through the sample; the second one requires the terahertz pulse transmitted through the sample and the second transmitted pulse after two reflections in the sample. However, in practice, there exists an angle between the incident terahertz beam and the surface normal of the sample. Yet, this angle is not easy to measure. So, in calculation we usually ignore this angle, which often causes error in the extracted refractive indices. In addition, this error is related with the selected method. In this article, after analyzing deviations of the refractive indices resulting from the angle when using the two methods, we propose a method to correct the extracting refractive indices. Our method could theoretically eliminate errors that are caused by the angle. Experiments further prove that this correction method is effective.