Refractive index measurement based on multi-wavelength laser interferometer

Abstract

The traditional methods of measuring refractive index have their unique value and advantages. In order to study the properties of materials and the application of multi-wavelength laser interferometer, a new method of measuring refractive index and dispersion of materials is proposed. The multi-wavelength laser interferometer is designed and built based on the principle of the Fizeau interferometer. It integrates five kinds of laser bands with a wide coverage range through a splitting prism, and can quickly change the measurement wavelength during remeasurement and improve the detection efficiency. In order to further verify the refractive index measurement method, a parallel plate is taken as an example to measure the refractive index. The multi-wavelength laser interferometer combined with variable wavelength standard spherical mirror is used to measure the displacement of ray focus in the case of parallel plate or not, and the refractive index of parallel plate is calculated by geometric optics. The refractive index corresponding to each wavelength is measured, and the refractive index curve of the parallel plate material is calculated by Conrady formula and ACF formula by fitting polynomial method using the measured data, and then the dispersion coefficient of the material can be calculated. The comparison results show that the ACF formula can be used to calculate the refractive index of materials accurately in a larger band range. The experimental results also show that the multi-wavelength laser interferometer has the advantage of measuring multi-wavelength transmission wavefront and can also play a role in more measurement applications.