Study on measurement method of laser beam quality parameter

Laser beam quality is an important technical specification, which consists of parameters of beam mode, centroid, beam width and beam divergence angle and etc. The working principle of laser beam quality analyzer and two methods (secondorder quadrature and knifeedge method) for beam width measurement common used nowdays are presented. The beam quality of low level laser was measured with the two methods. The maximum and minimum width average values are 2.55E+0.3μm and 1.50E+03μm, the maximum and minimum divergences are 2.13mrad and 1.25mrad measured by the secondorder quadratare method; the maximum and minimum width average values are 2.43E+03μm and 1.48E+03μm, the maximum and minimum divergence are 2.03mrad and 1.24mrad measured by knifeedge method.The variation of centroid at x and y directions are 0.03mm and 0.01mm measured by the secondorder quadrature method,and the variation of centroid at x and y direction are 0.02mm and 0.00mm measured by knifeedge method.The results show that the variation of the light spot centroid is ver small.The value of M2factor is 2.53, larger than 1, not Gauss so laser bean is idea fundamental mode.