基于液晶波片的近红外偏振分析器  

Near Infrared Polarimeter Based on Liquid Crystal Variable Retardes

作　　者：张志勇[1,2] 邓元勇[1,2] 王东光[1,2] 孙英姿[1,2] 玄伟佳[1,2] 

机构地区：[1]中国科学院国家天文台,北京100012 [2]中国科学院太阳活动重点实验室(国家天文台),北京100012

出　　处：《中国激光》2010年第3期696-702,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金天文联合基金(10778723;10878016);青年基金(10803012);中国科学院国家天文台青年人才基金资助课题

摘　　要：应用偏振分析器精确测量太阳光的偏振状态,并利用塞曼效应原理可以反演出太阳大气中的磁场形态,进而可以研究太阳黑子、耀斑及日冕物质抛射(CME)等活动现象。近红外波段观测是太阳物理研究的前沿领域,研制该波段偏振分析器可以获得比可见光更为丰富的信息,有利于解决太阳物理的基本问题。用一片λ/2与一片1λ可调相位延迟向列液晶波片(LCVR)组合,作为电光调制系统,并选用近红外波段消光比为10-5的偏振片作为检偏器,构成近红外偏振分析器。建立了精度为±0.01℃恒温控制系统。设计了电光调制方案,并对液晶波片的相位延迟与驱动电压的对应关系进行了精确定标。误差分析表明该方案交叉串扰(crosstalk)可到10-3量级,满足设计需求;与传统电光晶体KD*P等相比,液晶波片具有仅需低压调制、相位延迟连续可调、近红外波段透过率高、能够形成大口径等优势;同时由于无需机械移动部件,因而测量各斯托克斯(Stokes)参量间切换速度达到了毫秒量级,比机械移动调制形式的速度提高了2个数量级,从而可提高仪器测量的时间分辨率。Measuring the polarization states of the sunlight with a polarimeter,one can obtain the magnetic field information in the solar atmosphere using the principle of Zeeman effect and study the solar activities such as sun spots,flares and coronal mass ejection（CME）.Near infrared polarization measurement has been becoming the frontier and hot point in solar physics.Developing polarimeter at this wavelength can help us to get far more information than visible light and redound to resolving the basic problems of the solar physics.A newly developed near infrared Stokes polarimeter is presented in this paper.In this device,a λ/2 and a 1 λ liquid crystal variable retarders（LCVRs） are employed as the electro-optical modulators and a near infrared polarizer whose extinction ratio is about 10-5 as the analyzer and the temperature control system can keep the temperature within ±0.01 ℃,which satisfies the system designs.Compared to the commonly used KD＊P electro-optical modulators,liquid crystal retarder can reach any retardation between 0 and maximum only with low modulating voltage and has better transmittance and lager aperture.Furthermore,without any movement units,the speed of alternating the Stokes parameters is significantly improved by 102.And theoretical analysis shows that the crosstalk of this design is limited in the order of 10-3.

关 键 词：应用光学 偏振分析器 液晶波片 近红外 

分 类 号：TN216[电子电信—物理电子学]