对现有折射率的测量技术进行分析, 提出了一种测量两种透明介质间微小折射率差的新方法。首先, 介绍了微小折射率差干涉测量方法的原理, 并对该测量原理利用Zemax光学仿真软件进行了理论模拟论证。该实验中首先, 采用热键合技术制备包含两种被测量材料的组合平板; 其次, 利用干涉测量仪及外光路测量样件界面区域不同入射角下的光程差; 再者, 利用几何光学中的折射定律, 推导折射率分布与干涉光程差的关系式。最后, 通过二次曲线拟合获得正入射时的光程差微小变化值、换算得到样件两种材料的折射率差值。实验测量了1 at.%Yb3+: :YAG晶体与YAG晶体的热键合样品的折射率差, 测量值为5.41×10-5, 测量系统精度10-7量级。结果表明: 该测量方法原理简单、操作简便, 测量精度高。

A novel method to measure the refractive index distribution of two transparent mediums was proposed in this paper after analyzing measure methods of refractive indexes in existence. The basic principle and interferometry method of the measurement of micro refractive index change between two transparent mediums were described, and the theoretical feasibility of this measurement method was studied by using Zemax optical simulation software. Firstly, in this experiment, a composite plate from two transparent mediums to be measured was prepared by adhere-free bonding technology. Secondly, the optical path difference caused by the refractive index difference in the bonding interface was measured with the help of interferometer, under the different splitting angles of the composite plate. And then, the relational expression between the refractive index distribution and the optical path difference was deduced by using the law of refraction in geometrical optics. At last, the micro difference value of the optical path difference for normal incidence was obtained by conic approach technique in dealing with measuring data, and thus the final result of refractive index difference between two transparent mediums was obtained according to the conversion expression. The measured value of refractive index difference of a 1 at. % Yb3+: YAG/YAG bonded sample was also gotten and the value was 5.41×10-5, thus the accuracy of measurement system was up to 10-7 magnitude. The experiment result shows that the measurement method is simple, easy operation and has high precision.