We studied the influence of thermal birefringence-induced bifocusing on optical beams. An analytical model was developed to describe the bifocusing aberration. With this model we determined the circle-of-least-confusion location and the amount of beam quality degradation expected. A numerical model was developed to describe wave-front deformation by a bifocal lens and the intensity distribution at the foci of the polarization components—radial and tangential as well as at the circle of least confusion. Model predictions for beam quality degradation and intensity distributions along the focal range were confirmed experimentally using a strongly pumped Nd:YAG rod as a bifocal lens. It is shown that bifocusing is an important aberration in high-power rod-based lasers that must (and can) be corrected to achieve high beam quality.
© 2005 Optical Society of America
Inon Moshe and Steven Jackel, "Influence of birefringence-induced bifocusing on optical beams," J. Opt. Soc. Am. B 22, 1228-1235 (2005)