In this work we implement a Mach–Zehnder interferometer with an image rotator in one of its arms to measure the orbital angular momentum (OAM) spectrum of a partially coherent beam. By measuring the visibility of the interference as a function of the angle of rotation, the OAM distribution can be recovered via a Fourier transform. Theoretical calculations based on the coherent mode decomposition of the cross-spectral density are in excellent agreement with the experimental data.
© 2010 Optical Society of America
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