The ability to generate and then amplify radially polarized light opens up the possibility of achieving very high-power, near diffraction-limited beams from rod-based solid-state lasers. Residual bifocusing rapidly degrades beam quality. Residual bifocusing results from nonradially symmetric pump distributions. We analyze how a nonradially symmetric pump distribution induces a nonradially symmetric stress map. This manifests itself as nonradially symmetric birefringence, and as depolarization to radially/azimuthally polarized beams (or as deterioration in birefringence compensated linearly polarized lasers). Here we analytically describe the birefringence terms of a nonradially symmetric strain map. The model results are supported by radial-depolarization measurements in our Nd:YAG pump chambers. For the current level of depolarization, beam quality degradation per rod is because of bifocusing alone. The degradation per rod can be reduced substantially by improving pump uniformity.
© 2008 Optical Society of America
Equations on this page are rendered with MathJax. Learn more.