9.4 - An investigation of laser wave depolarization due to atmospheric transmission

A theoretical and an experimental analysis of optical depolarization due to atmospheric transmission is given. We used the geometrical optics approximation and applied Chernov's three-dimensional ray statistics model for the calculations. The theory predicts that the root-mean-square change of the polarization angle of an optical beam propagating through the atmosphere is of the order of 10
^-9
rad/km. This was found to increase linearly with the path-length. The experiment was designed to measure the amount of depolarization of a linearly polarized laser wave propagating through the atmosphere. The measurements over a 2.6-km path length indicated the absence of such an effect. The sensitivity of these measurements was limited by the equipment used to -42 dB in the daytime and to -45 dB at night.