Study on thermally induced depolarization of a probe beam by considering the thermal lens effect

Abstract

In this paper, we present an accurate theoretical description of the birefringence characteristics in a Nd : YAG rod by taking the thermal lens effect into account. Considering that the birefringence is strongly dependent on the distance away from the centre of a birefringent rod, the convergent features of an incident probe beam were first evaluated for a side-pumped laser rod. A segmental accumulation method was then employed to calculate the total phase shift between the radial and the tangential components of polarization of a converged probe beam. The theoretical conclusions were compared with the measured results in both the degree of depolarization and the spatial birefringent distribution of a transmitted He–Ne laser beam. The experimental results are in good agreement with the theoretical ones so that we believe the algorithm given in this paper should be effective for the construction of a high-powered laser or amplifier system.