1 May 2014 Characterisation of birefringence of [111]-cut crystal rod using side-pumping and crystal rotation
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Birefringence influences the beam quality and output power of high power solid-state lasers. Inhomogeneous distribution of the thermal field inside the laser crystal rod leads to thermal strains and birefringence, due to the photoelastic effect. Analytical models have used the plane stress and plane strain assumption for an axial sym- metric pumped crystal. This leads in case of an [111]-cut to an axially symmetric birefringence pattern. However, numerical calculations of birefringence show a threefold symmetry pattern due to the anisotropic behavior of the photoelastic tensor. This disturbs the ideal use of a radial or azimuthal polarised beam. We analyzed a laser rod pumped at three sides with threefold symmetry, in order to reduce the effect of birefringence. Simulation results show birefringence is affected by rotation of the crystal around its [111]-axis. Smallest birefringence can be obtained by an optimal rotation with respect to the edges of the crystal. Therefore the output beam of this laser device is more suitable for generating radial or azimuthal polarisations.
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Thomas Graupeter, Thomas Graupeter, Rainer Hartmann, Rainer Hartmann, Christoph Pflaum, Christoph Pflaum, } "Characterisation of birefringence of [111]-cut crystal rod using side-pumping and crystal rotation", Proc. SPIE 9135, Laser Sources and Applications II, 91351L (1 May 2014); doi: 10.1117/12.2052268; https://doi.org/10.1117/12.2052268

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