Spot-dancing and Related Saturation Phenomenon of Irradiance Scintillation of Optical Beams in a Random Medium

The irradiance probability distribution is analytically derived for the phase structure function having a quadratic form and for the wave beam having a circular or elliptical cross-section, and is illustrated for a few typical cases. When the relevant parameter E, representing the magnitude of wave fluctuation, has sufficiently small values in the range of E 1, the irradiance distribution can be close to the log-normal distribution. When E d 1, on the other hand, it gives rise to the so-called spot-dancing, and the log-irradiance is uniformly distributed in the important range of values of interest. The saturation phenomenon is also investigated for both irradiance and log-irradiance scintillations; it is found that the normalized variance of the irradiance scintillation shows a clear saturation in a wide range of the parameter E, although the variance ultimately does not tend to a finite value as E M X. On the other hand, the variance of the log-irradiance does not show any saturation.