Analysis on the thermal effect of dual-end pumped Tm:YLF crystal

Abstract

The theoretical model of thermal-steady-state anisotropic Tm:YLF crystal was built based on the practical operation condition. Integral transformation was used to get the analytical expression of the distribution of temperature in Tm crystal and thermal focal length. Matlab was used to simulate the influence of pump power density, crystal length and doping density to the distribution of temperature and thermal focal length. The results showed that under the invariant pumping power density and crystal length, the temperature rise and nonuniformity of thermal distortion are intensified by the increase of doping density which leads to a worse thermal effect. Under the invariant pumping power and doping density, the temperature rise and nonuniformity of thermal distortion are weaken by the modest increase of crystal length which leads to a good thermal condition. When the product of crystal length and doping concentration is a constant value, the thermal focal length keeps basic consistent. Furthermore, the simulated results are that when the dual-pumped power is 60W and waist radius is 430μm, the thermal focal length of 12mm, 3at.% doped which perpendicular and parallel to c axis are 184mm and 261mm respectively, and the thermal focal length of 12mm, 3.5at.% doped which perpendicular and parallel to c axis are 171mm and 243mm respectively. The results in this paper provide theoretical basis for thermal compensation and cavity design of dual-pumped Tm:YLF laser, meanwhile, the model built can be used to analyze other anisotropic crystals.