Peculiarity of the thermally induced depolarization and methods of depolarization compensation in square-shaped Yb:YAG active elements

The degree of thermally induced depolarization for square disc-shaped Yb:YAG active element was calculated. Its dependence on the volume density of heat release in the active element was considered. The dependence of the thermally induced depolarization on the number of active elements and input polarization orientation was investigated. It is shown numerically that use of incoming polarization orientation at an angle of 45 degrees relative to the sides of the element is optimal in terms of minimizing thermally induced depolarization. A review of thermally induced depolarization compensation schemes is presented.