一种基于衍射光栅光束质量M^2因子的实时检测技术

Real-Time Measurement of Beam Quality Factor M^2 Based on Diffraction Gratings

提出了一种新的光束质量M2因子实时检测技术,利用一个普通正交衍射光栅组将一束待测激光束分成3×3共9路光,并利用光路调整器使9路光束通过不同的光程后有序地排列在CCD相机的探测面上,并使得各路光的光程差分布在束腰附近两倍瑞利距离内,从而可利用单一CCD探测面来同时获取待测光束多个位置上的光斑图样,再利用二阶矩理论求出各个位置上的光束束宽,通过曲线拟合进而实现光束质量的实时检测。结果表明,对于连续He-Ne激光器的输出光束,采用实时检测技术得到的测量结果与用传统方法得到的结果基本一致。

A new technique for real time measurement of beam quality factor M^2 is presented. The laser beam is divided into a set of 3 × 3 beams by two gratings arranged orthogonally. Then, this 3 × 3 beams are rotated by a beam steering so that they arrive at the charge-coupled device （CCD） camera with various optical paths. The maximum optical path difference is approximately twice as much as the Rayleigh range. Thus the beam spots at various positions can be retrieved by a single CCD camera simultaneously. And their widths can be calculated by the second moment method. At last, the beam quality factor M^2 is retrieved by the curve fitting method. The measurement result of a continuous wave （CW） HeiNe laser beam agrees well with that using conventional technique.