Efficient continuous wave deep ultraviolet Pr 3+ :LiYF 4 laser at 261.3nm

We report continuous wave deep ultraviolet laser operation at 261.3nm by intracavity frequency doubling of laser diode pumped Pr 3+ doped LiYF 4 lasers. Using two InGaN laser diodes with a maximum output power of about 1W each, a 2.9mm long Pr 3+ :LiYF 4 crystal and a 5mm long beta-barium-borate crystal, coherent radiation with an output power of 481 mW at 261.3nm was achieved at an optical-to-optical efficiency of 26.1% with respect to the total pump power. Both, linear and nonlinear losses have been calculated to be approximately 0.6% by using a model for intracavity frequency doubling with focussed Gaussian beams.