Abstract

Thermal effects in optical mediums became more and more important in applied optics because of quick and steady grow of average power of modern lasers. Radiation power is so high that phase distortions caused by thermal lensing effects became important for achieving lasers resonators stability. In this paper we discuss interesting experimental results for YLF crystal: high anisotropy and high astigmatism of thermal lens in a-cutted YLF rods. The first effect is more or less predictable because YLF is uniaxial crystal. But high astigmatism of thermal lense is unexpected and is not explained in literature so far. Astigmatism is so high that phase distortions profile for perpendicular directions can change its sign [1-3]. Unfortunately in most papers the reason of thermal lens astigmatism is not discussed. At some papers there is a try to explain this by thermal conductivity anisotropy and as a result – non-symmetric temperature distribution but this effect is unable to change the sign of the lens.

© 2009 IEEE