Crystal Refractive Index Measurement Method

The refractivity of crystal is one of the most important optics parameter and it is also one of the most basic content to judge the physical characteristics of crystal. To the same crystal, if the wavelength different then we get the different refractivity, the measurement of refractivity is vital to design device. There are many methods to measure the refractivity of the crystal, however, the accuracy and the range of the measurement of refractivity subject to deferent extent limitation because of the methods built-in conditions.Birefringence is an important optical parameter of nonisotropic crystal, which is determined by multi factors, such as component structure growth condition and wavelength. There are many methods to measure birefringence, but they usually applicable for single wavelength and birefringence is obtained by primary refractive index, precision generally is 10^-4. The accurate method is interferometry, for example, steep interferometry and self-compensation interferometry, they have a common characteristic that the precision can increase one or two order, but they are only applicable for visible light and sample precision demand is high, crystal techniques is difficult to meet, so measure precision is far form theory precision. We adopt continuous polarization principle to measure birefringence of crystal, the sample is only an even thin board which optical axis is parallel to the surface, the construction is simple and the technique data is easy to control. The range of measurement is not only visible light, but also ultraviolet band and infrared region. We can get birefringence of 10^-5 precision without complex data-processing.The paper includes five sections. In the first chapter we introduce the concept of refractivity and the methods to measure the refractivity. In the second chapter, we give the theories of birefringence and the application of birefringence phenomenon. In the third chapter, we collate any typical methods to measure the refractivity. It also includes the method we use to measure birefringence in the fifth chapter. In the fourth chapter, we put forward the new methods to measure the refractivity of the specimen materials, the difference of light intensity method and the vertical incidence method. In the last chapter, by using polarization interfering method to measure the birefringence of quartz, we get birefringence of 10^-5 precision. And we get a new viewpoint about the convergence characteristic of the experiment curve.The main innovations of this article is first, the first one who put forward two easy methods, the difference of light intensity method and the vertical incidence method, to measure the refractivity. Second, we make theoretical analysis to the variable characters of the light intensity transmissivity curve which is gained through the continuous polarization interfering experiment. Through changing experiment conditions, we find that the intensity transmission curve vary along with the slit and appear a definite rule. It turns that the main factor is the monochromaticity of the light. Material absorb is the secondary.