KDP晶体折射率非均匀性检测系统

Testing of KDP Crystal Refractive Index Nonuniformity

基于正交偏振干涉法,建立了KDP晶体折射率非均匀性的检测系统,并可实现晶体相位失谐角的间接检测.波前检测系统实现了测试光偏振态的精密控制与切换,采用波长调谐相移的方法去除了测试过程中参考面倾斜引入的误差,优化了抗振动相移算法,提高了波前测试的测量准确度及重复性.通过折射率非均匀性分析算法的设计,解决了晶体厚度变化引入的误差等.小口径晶体元件的测试结果表明系统的折射率非均匀性检测准确度(均方根值)优于10-6.

Based on a method named Orthogonal Polarization Interferometry, testing system on refractive index nonuniformity of KDP crystal is proposed, and phase detuning angle can also be indirectly tested. Polarizaton state of the testing light is precisely controlled and switched in the interferometer. Error introduced by tilt of the optical element is avoided by adopting wavelength-tuning phase shifting method. Phase shifting algorithm is optimized to raise testing precision and repeatbility. Analytic algorithm of index of refraction nonuniformity is designed, and therefore the error introduced by variation in the crystal thickness is avoided. The measurement result for the crystal with small aperture shows that the accuracy of the instrument is better than 10^-6 （RMS）.