Motion of hot spots in smoothed beams

We develop a statistical model that describes the motion of a hot spot crea ted by smoothing techniques. We define clearly the transverse and longitudi nal instantaneous velocities of a hot spot and quantify its Lifetime. This relevant parameter is found to be longer than the laser coherence time defi ned as the inverse of the spectrum bandwidth. We apply this model to the mo st usual smoothing techniques, using a sinusoidal phase modulation or a ran dom spectrum. We give asymptotic results for hot spot velocities and lifeti me for the cases of one-dimensional smoothing by spectral dispersion, smoot hing by longitudinal spectral dispersion, and smoothing by optical fiber. ( C) 1999 Optical Society of America [S0740-3232(99)02607-1].