Calculations of Eigenpolarization in Nd:YAG Laser Rods Due to Thermally Induced Birefringence

Laser crystals like Nd:YAG are widely used in laser resonators. The stress-induced birefringence of such laser crystals has a strong influence on beam quality, power, and polarization of the output laser beam. Detailed simulations using 3-D finite-element analysis and a 2-D Jones matrix analysis were performed to analyze these effects. The finite-element analysis is used to calculate stress and birefringence depending on the cut direction of the crystal and its rotation. Eigenvalues and eigenvectors of the electromagnetic field inside the resonators are calculated by Jones matrix analysis. The analysis includes resonators with Brewster plates. Output power and beam quality are calculated by dynamic multimode analysis. Simulation results are presented for [100]-cut, [110]-cut, and [111]-cut Nd:YAG crystals.