Compensation of thermally induced birefringence in polycrystalline Nd:YAG ceramics

Summary form only given. Recently polycrystalline Nd:YAG ceramics used as an active medium has attracted much attention because of several essential advantages in comparison with a Nd:YAG single crystal. The given work is devoted to a detailed theoretical study of thermally induced depolarization in Nd:YAG ceramics and specific features of its compensation by the well-known technique with a 90 degree rotator. We derived analytical expressions for phase delay and eigen polarizations in grains of thermally loaded Nd:YAG ceramics rod. These formulas allow to calculate output polarization of laser radiation, which depends on a dimensionless heat release power p and parameter N - ratio of the rod length to mean grain length (l). Both polarized and depolarized radiation always have small-scale modulation with a characteristic size of less (l) and modulation depth depending on N. Two laser rods with a 90/spl deg/ rotator between them do not provide full birefringence compensation. An increase in N is expedient from the viewpoint of both diminution of depth of the modulation and birefringence compensation.