Optical EngineeringPractical use of the spatial coherence function for determining laser transverse mode structure
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The spatial coherence function of a beam exiting from a wave-guiding device can be used to determine the transverse modal composition of the fields which are supported within the structure. The strength of the spatial coherence technique is that it directly yields the relative modal weights which exist within the cavity. While this technique has received little attention in the past due to the experimental difficulties in measuring spatial coherence, a recently developed technique overcomes several of these problems. We demonstrate how the relative modal amplitudes may be extracted from the spatial coherence function for the case where the field distribution is described by Hermite-Gaussian polynomials. We point out some limitations of this method and discuss how these may be circumvented.