Thermally induced stresses and birefringence in Nd laser rods

Heat accumulation during optical pumping of Nd laser rods produces an inhomogeneous temperature distribution across the rod. This results in thermally induced stresses, which in turn produce changes in the refractive indices of the rod material. Thus, the optical path length varies resulting in tangential polarizations of a beam entering the rod. This affects the mode distribution of the laser output beam. Consequently, the present study examines the temperature distribution across the laser rod due to single and pulsed operation. The resulting thermal stresses and birefringence are computed across the rod. It is found that the birefringence occuring at the rod center is zero and increases to 13 wavelengths at the rod radius.