中文摘要：

在基于Kramers-Kronig（K-K）关系求解太赫兹（THz）频段介质的折射率和吸收系数时,针对反射率高频端外延指数函数的指数因子的确定问题,提出采用时域有限差分（FDTD）算法模拟优化指数因子的方法,从而保证提取介质折射率和吸收系数的精确性.该方法根据FDTD算法模拟与实测样品时域信号的最小二乘差来确定指数因子,当最小二乘差取极小值时所对应的指数因子即为最优解.葡萄糖多晶粉末压片的实验表明,采用本文所提出的利用FDTD算法模拟优化确定的指数因子为0.495,当用K-K关系求解折射率和吸收系数时得到的结果更加精确.

英文摘要：

Kramers-Kronig can be used to extract refractive index and absorption coefficient of medium in terahertz（THz）region.But it is needed for reflectance to set up an extension function at high frequency.The exponential function is a kind of empirical extension function.In general,the index factor of exponential function is 2or 4.In this paper,the optimized method used for the algorithm of finite difference time domain（FDTD）is proposed to determinate the index factor.Accuracy of refractive index and absorption coefficient is improved by this method.Determination of index factor is based on least square difference between simulation and measured time domain signals.The index factor corresponds to the minimum of least square difference.Experiment of shows glucose polycrystalline pellet that accuracy of refractive index and absorption coefficient is guaranteed when the optimized index factor is 0.495.This method provides a reference to extract refractive index and absorption coefficient of medium by Kramers-Kronig relation in the THz region.