Research On The Key Techniques Of The Micro-Birefringence Parameters Detection

Birefringence is a phenomenon in which beams are decomposed into two types of polarized light,o light and e light,which are perpendicular to each other and have different refractive indices when they enter an anisotropic crystal.They are widely used in ultra-high resolution imaging,micro-nano processing,integrated circuits,aerospace and so on.Micro-birefringence is an important index for evaluating the optical uniformity of optical materials and devices.The detection of this parameter will facilitate better analysis of the quality and performance of optical materials and devices.In order to make up for the low sensitivity of polarized light interferometry,electro-optical modulation and photo-elastic modulation are gradually applied to the birefringence and uniformity detection of optical materials.Therefore,this paper proposes a high-speed,high-precision,high-sensitivity micro-birefringence detection method based on the combined modulation of photo-elastic modulator and electro-optic modulator.This article mainly from the following aspects to expand the elaboration.At first,the working mechanism and model of photo-elastic modulator and electro-optical modulator are firstly analyzed.A novel birefringence detection method and system model based on combined modulation of photo-elastic modulator and electro-optical modulators are presented.Secondly,according to the frequency drifting characteristics of photo-elastic modulator,based on the model of dynamic heat exchange and the model of resonance equivalent of photo-elastic modulator,a PEM driving voltage self-regulation method based on voltage compensation is proposed.Thirdly,the FPGA is used as the core to design a data processing module.In this module,the DC component,the fundamental frequency component and the double-frequency term ofthe modulated signal are obtained through a detector,a signal conditioning circuit,and a dual AD acquisition module.The modulated signal and the reference signal are simultaneously obtained.The digital phase-locked is completed in the FPGA,and the result is transferred to Labview through serial communication module for data processing,and finally the detection of the Micro-birefringence parameters is obtained.Finally,A Micro-birefringence parameter detection platform was built to test the stability of the Micro-birefringence detection system,and then the measurement accuracy of system was analyzed.It is showed in the experiment that the changed amplitude of phase retardation amount during voltage compensation is 0.6%,but the amplitude of phase retardation decreases by 15.6% in the constant drive voltage.It proves that the method effectively stabilizes the phase retardation and improves the stability and modulation efficiency of the Micro-birefringence detection system.