Beam waist and M2 measurement using a finite slit

Laser beam profiling can be accomplished by several techniques, which have different degrees of accuracy. For the description of near-Gaussian beams using the M² parameter, the scanning slit method is a convenient and accurate profiling technique. The profiling of a tightly focused Q-switched laser beam is described. It is possible to correct very simply for the finite slit size, and it is not necessary for the slit width to be much less than the waist radius. This correction can also be applied in the CCD camera measurement technique, in which some correction can be made for the nonzero pixel size.