Depolarization induced by pump edge effects in high average power laser rods

Abstract

Non-radially symmetric residual birefringence in laser rods due to pump edge effects is analyzed both theoretically and experimentally. For cubic crystals such as yttrium aluminum garnet (YAG), this depolarization has a unique sixfold symmetry that is closely connected to the crystal's cubic symmetry. While this depolarization is small compared to that observed with linear or circular polarizations, it is measurable and important when using radial or azimuthal polarizations in rods generating heat powers in excess of 70 W/cm. A simple criterion was defined in order to help estimate the amount of depolarization in a high-power laser rod system.