Fluoride crystals: materials for near-infrared solid state lasers

摘要

In this work we present an overview of the best 2μm laser results obtained in Tm-doped fluoride hosts LiYF_4(YLF), LiLuF_4 (LLF) and BaY_2F_8 (BYF) and we report on the growth, spectroscopy and first laser test emission of a novel mixed material BaYLuF_8 (BYLF), interesting as a variant of BYF material with a partial substitution of Y~(3+) ions by Lu~(3+). The novel host is interesting mainly because indications are that the mixed crystal would be sturdier than BYF. The addition of Lutetium would improve the thermo-mechanical properties going into the direction of high power applications, as suggest from works on YLF and its isomorph LLF. A detailed description of Czochralski growth of fluoride laser materials is provided, focusing on the growth parameters of the novel BYLF:Tm~(3+)12% material grown. With regard of spectroscopy analysis, we report on the results obtained with BYLF host. Detailed absorption, fluorescence and lifetime measurements have been performed focusing on the ~3H_4 and ~3F_4 manifolds, the pumping and upper laser level. Moreover diode pumped CW laser emission at 2 μm has been achieved in BYLF: Tm~(3+)12% sample obtaining a slope efficiency of about 28% with respect to the absorbed power.