Abstract

We compare the classical technique for determining the coherence length of semiconductor laser light based on the slope of the interference-fringe visibility curve against a speckle technique based on the number of connected domains in the speckle-field interference pattern as determined using the morphological Euler number. The study was performed using a Michelson interferometer where the difference in optical path length between the legs can be adjusted over a range of several centimeters. We report the results from a comparison of these techniques for determining coherence of radiation from semiconductor lasers in the red (650 nm), green (532 nm), and blue (450 nm) regions. We show that the interference-fringe visibility curves and the curves for the morphological Euler numbers as a function of the phase delay induced by the adjustable arm of the interferometer are clearly correlated. The morphological radiation-coherence determination technique based on the speckle-field interference pattern is quite fast and is simpler than the traditional interference-fringe contrast-visibility technique.

© 2016 Optical Society of America

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