Magnesium fluoride (MgF2) is a widely used optical window material in lasers. Laser-induced damage in MgF2 materials involves complex thermal-mechanical coupling issues. With the rapid development of high-power fiber laser technologies and application of optoelectronic countermeasures, it is necessary to investigate the damage mechanism of 1.06 μm high-power continuous-wave laser on MgF2 optical windows to clarify the laser damage threshold and factors influencing laser-irradiated MgF2 window mirrors. Therefore, based on the theory of heat conduction and elastic mechanics, a simulation study was conducted using the finite element method. First, based on the thermo-mechanical theory, established a thermo-mechanical damage model for a laser-irradiated MgF2 crystal. Second, we calculated the temperature, stress, and strain fields of single-crystal MgF2 material under the action of a 100 W / cm2 laser. When the laser was irradiated for 4.921 s, thermal stress-induced burst damage was observed, but no melting damage occurred. Finally, the impact of parameters such as the laser power density, spot size, and laser action time on the damage effect was discussed using the parametric scanning method. The calculation results showed that the aforementioned factors significantly impact the damaging effect. Moreover, under the same laser parameters, material burst due to thermal stress is expected to precede the melt damage.
Diode-pumped alkali vapor lasers are famous in the field of laser for their significant advantages such as very high quantum efficiency (Cs 99.5%, Rb 98.1%, K 95.2%), good thermal management performance and excellent beam output quality etc. A rate equation model fully considering the spatial distributions of pumping light and oscillating light is established under the hypothesis of quasi-two-level energy system of DPALs in this paper. Meanwhile, expressions of threshold pumping power, mode-matching efficiency and output power and slop efficiency in low pumping and strong pumping, respectively, are obtained. Then, the influences of mode-matching efficiency on working performance of DPALs are discussed and analyzed. Results show that mode-matching efficiency mainly impacts on threshold pumping power, output power and slop efficiency in low pumping but that nearly has no effects in strong pumping. Therefore, this model benefits the further research of DPALs.
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