Method and devices for examining the relative radiation flux density of electromagnetic beams, especially for determining the radius of Gaussian laser beams

摘要

For determining the radiation density of electromagnetic beams, especially for determining the radius of Gaussian laser beams, a scattering surface is placed in the beam. Beam and scattering surface move relative to each other. The light scattered by the scattering surface in a specific angular range reaches a detector which enables the measurement of the random fluctuations of the scattered light, for example by measuring the time-autocorrelation function of the scattered light. These random fluctuations are produced because the scattering properties of the scattering surface have a random location dependence (for example because of surface roughnesses) and the radiation flux density is likewise location-dependent. By means of the relative movement, parts of the scattering surface pass through regions of different radiation flux density. If the relative velocity is known, the beam radius can then be determined in a simple way by measuring the time-autocorrelation function of the scattered radiation in Gaussian beams. Deviations from Gaussian beams can thus also be determined.