为实现激光棒透射波前的测量, 改善一般泰曼型或斐索型干涉仪测量小口径激光棒透射波前时的边缘衍射效应, 研究了一种变倾角移相马赫-曾德尔干涉仪。通过调整移相反射镜的倾斜姿态, 改变入射到马赫 -曾德尔干涉光路的光束倾角, 参考光束与测试光束的光程差随之变化, 从而在相干光之间引入相移, 实现了相移干涉测量。利用该干涉仪测量一根口径为 Ф6 mm、长度为 60 mm激光棒 (Nd:YAG)的透射波前, 测量结果的峰谷值(PV)为 0.391λ, 均方根值(RMS)为 0.056λ; 使用 ZYGO激光干涉仪测量同一根激光棒, 其透射波前的峰谷值(PV)为 0.370λ, 均方根值(RMS)为 0.064λ。对比结果表明该干涉仪能实现光学元件透射波前的高精度检测, 测试结果的一致性验证了该方案的可行性。该变倾角移相方法具有较高的移相精度和较大的移相范围, 且该变倾角干涉系统中光束仅一次透过待测激光棒, 可有效抑制多光束干涉现象, 改善小口径激光棒的边缘衍射效应。

In order to measure the transmission wavefront of laser rods and to improve the edge diffraction effect of small-aperture laser rods measured by Tayman or Fizeau interferometer, a variable-inclination Mach-Zehnder inter-ferometer was proposed. The incident angle was changed by adjusting the tilting attitude of the phase shifting ref-lector, then the optical path difference was changed that the phase shift was introduced to the coherent light and the phase shifting interferometry was realized. The transmission wavefront of a laser rod (Nd:YAG) with the diameter of 6 mm and the length of 60 mm was measured by this interferometer, the peak-valley (PV) and root mean square (RMS) of the wavefront were 0.391λ and 0.056λ. The same laser rod was measured by ZYGO GPI XP interferometer, the peak-valley (PV) and root mean square (RMS) were 0.370λ and 0.064λ. The comparison results show that the interferometer can achieve high-precision detection of transmission wavefront of laser robs. The variable-inclination Mach-Zehnder interferometer has high phase-shifting precision and wide phase-shifting range, and the beam in the system can pass through the laser rod only once, which can suppress the multi-beam interference and improve the edge diffraction effect of the small-aperture laser rods.