We are using double-beam interferometric and intensity correlation methods to study the phase and amplitude changes of laser beams that have propagated along short paths through artificially generated turbulence. The results are compared with analytic theory and with Monte-Carlo simulations of the turbulent medium. If the two beams in a double-beam interferometer pass along identical paths, they should be immune to turbulence, as both beams acquire identical phase modulations and phase-front distortions. However, the time-averaged fringe visibility should degrade as the two beams are laterally separated. We have previously described our preliminary work with a modified Mach-Zehnder interferometer in which the lateral separations of the laser beams in two arms containing a turbulent medium could be continuously varied from zero.1 We measure the change in fringe visibility that occurs as the beams are laterally separated in various levels of artificially generated turbulence in a liquid or gaseous medium. It is not easy to assure that artificially generated turbulence satisfies the conditions for an analysis assuming fully developed Kolmogorov turbulence.2 These measurements are correlated with measurements made of the relative turbulence strength by performing a statistical analysis of intensity fluctuations of the laser beam in one arm of the interferometer to determine a parameter.
© 1991 Optical Society of AmericaPDF Article