Laser beam distribution in the focal region

The distribution of a focused Nd-glass laser beam has been determined by monitoring the radiation transmitted through an 11-micrometer diam pinhole during single shots at different positions in the focal region. The same pinhole was used throughout the measurements and because the pinhole was small compared to the beam diameter, off-axis irregularities were resolved. Fluctuations in power over a few microseconds due to individual output spikes were averaged out in time-resolved measurements to compare the pulse shape (1.4 microseconds in length) at different points in the beam. Disadvantages and advantages of the described method are evaluated.