Thermally induced birefringence in edge-pumped microchip Yb:YAG ceramic

In this paper, we report on the depolarization effects induced by thermal field established in the edge-pumped all ceramic composite Yb:YAG laser. Polycrystalline Yb:YAG ceramics consist of a number of single crystal grains under 80 mum size, separated by very thin borders. The main difference between ceramics and single crystal is that crystal axes in each grain are arbitrarily oriented. arbitrarily oriented. This leads to a random nature of the depolarization in ceramics. Since rays separated by a grain size distance passes through a set of grains randomly oriented a spatial modulation of the beam can be observed after the beam passes through polarizer and the depolarization, defined as the ratio of the depolarized power to the total probe power.