Calibration standard for laser beam profilers: method for absolute accuracy measurement with a Fresnel diffraction test pattern

Abstract

The absolute accuracy of a clip-level laser beam profiler is measured to the 0.3% level, by comparison of the profiler's reading to the known width of a Fresnel diffraction test pattern. A pair of opposed knife edges, illuminated by a quasi-uniform and quasi-plane wave, generates the pattern whose width is determined by the 50% cut points in translating the edge pair across a tightly focused beam. The convolution of the scanning aperture with the diffraction fringe pattern is modeled to remove the effect of the aperture size from the accuracy test and to give a means of measuring the aperture width. Discussions of the experimental aspects of this test method show it to be an acceptable calibration standard for optical profilers, of use to those working on the International Standards Organization draft standard for laser beam parameter measurements.