AN EXPERIMENT TO OBSERVE THE INTENSITY AND PHASE-STRUCTURE OF LAGUERRE-GAUSSIAN LASER MODES

We outline an easily reproduced experiment that allows the student to investigate the intensity and phase structure of transverse laser mode s. In addition to discussing the usual Hermite-Gaussian laser modes we detail how Laguerre-Gaussian laser modes can be obtained by the direc t conversion of the Hermite-Gaussian output. A Mach-Zehnder interferom eter allows the phase structure of the Laguerre-Gaussian modes to be c ompared with the phase structure of a plane wave with the same frequen cy. The resulting interference patterns clearly illustrate the azimuth al phase dependence of the Laguerre-Gaussian modes, which is the origi n of the orbital angular momentum associated with each of them. (C) 19 96 American Association of Physics Teachers.