| 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 technics 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 main innovation of this article is that through comparing several means to measure the most birefringence, bringing forward continuous polarization interfering to measure the most birefringence of crystal accurately. Through changing experiment conditions, we find that the intensity transmission curve vary along with the slit and appear a definite rule. We give qualitative analysis and theory explanation to it according to the laboratory instrument localization, the main factor is the monochromaticity of the light, crystal absorb is the side effect. |
