Coupled thermo-optical modeling of high-power operation of Tm,Ho: YLF solid state lasers

摘要

Integrated computational model for operation of co-doped Tm,Ho solid-state lasers is developed coupling (ⅰ) 8-level rate equations with (ⅱ) TEMoo laser beam distribution, and (ⅲ) complex heat dissipation model. Simulations done for Q-switched ≈ 0.1 J giant pulse generation by Tm,Ho:YLF laser show that ≈ 43 % of the 780 nm light diode side-pumped energy is directly transformed into the heat inside the crystal, whereas ≈ 45 % is the spontaneously emitted radiation from ~3F_4, ~5I_7, ~3H_4 and ~3H_5 levels. In water-cooled operation this radiation is absorbed inside the thermal boundary layer where the heat transfer is dominated by heat conduction. In high-power operation the resulting temperature increase is shown to lead to (ⅰ) significant decrease in giant pulse energy and (ⅱ) thermal lensing.