Measurement of the mode coherence coefficients

Based on average intensity distributions at two axial positions, an experimental approach to determine the mode coherence coefficients was developed. Using this approach, investigations were carried out for a CO₂ laser with a stripe resonator. The power partitions of, and cross-correlations between, modes at different aperture widths and the dependence of the beam quality on the aperture width were studied. The measuring principle, an iterative fit method, and some experimental results are presented and discussed.