A computationally efficient numerical simulation of a diode-pumped alkali laser (DPAL) has been developed. It considers the thermal lensing effect by a wave-optics optical resonator model coupled with a simplified gas-flow model. The calculation results indicate that the proposed gas-flow model correctly predicts the temperature distribution of the active medium heated by exothermic reactions. As a result, there is good agreement between the calculations and experiments, especially with the output power as a function of the gas-flow velocity. The calculations have shown that the population of the high-lying excited levels of the Cs atom is negligible within a pump power intensity of 10 kW/cm2.

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High-pressure subsonic mode operation of a chemical oxygen-iodine laser (COIL) was demonstrated. Singlet delta oxygen generated by a liquid-jet type singlet oxygen generator (SOG) was directly utilized in the laser cavity, without supersonic expansion. The operating pressure in the laser cavity was 0.80 kPa (6.0 Torr). Cooled nitrogen gas was added to the singlet oxygen flow to enhance the output power. An output power of 448 W was obtained for a chlorine input rate of 19.7 mmol/s. This is equivalent to a chemical efficiency of 25.0%, and it is comparable to the highest reported chemical efficiency of COIL using nitrogen as the buffer gas. The obtained value of specific energy of 3.5 J/liter, is more than fivefold higher than that for our supersonic COIL device.

We have developed a numerical simulation method for diode-pumped alkali lasers (DPALs). We previously reported the use of a simplified gas-flow model, whose adaptability was restricted to forced gas-flow DPALs. In the present study, we have employed an incompressible, three-dimensional computational fluid dynamics (CFD) model. The natural convective flow is modeled using a modified Boussinesq approximation. The results of the simulations were found to be in good agreement with those for a compressible CFD model for a heat-induced flow problem. As a result, good agreement with the experimental results was achieved for a sealed DPAL. On the other hand, the results for the forced gas-flow DPAL were the same as those for the simplified gas-flow model, which confirms the validity of the latter model. The dependence of the beam quality on the pump power for the sealed DPAL was consistent with previously reported results.