Measurement of birefringence of a single axis crystal varying with temperature based on double light paths

In order to measure the variation of birefringence varying with temperature when incident wavelength is fixed,firstly,the formula of the birefringence of a single axis crystal varying with temperature was deduced according to the theory of polarized light interference.Then an experimental system with double beam paths was set up for comparing measurement.With this system,a sample of quartz was measured and the curve of birefringence vs.temperature was drawn.After analyzing the test results,a formula of birefringence vs.temperature was obtained.The results indicate that,when the incident wavelength is fixed,the relationship between birefringence and temperature is linear.In the experimental process,if the instrument is regulated well and the temperature is contorlled properly,the test result is reliable.