Excitation mechanisms and gain modeling of the high-pressure atomic Ar laser in He/Ar mixtures

TLDR

High‑pressure (≥0.5 atm) atomic argon lasers emit on four infrared transitions from 1.27 to 2.4 µm. The authors developed a computer model to investigate the excitation mechanisms of the high‑pressure Ar laser. The model analyzes gain and laser oscillation in He/Ar mixtures across varying argon mole fractions and total pressures, comparing predictions with experimental data. The model shows that the 1.79 µm transition is predominantly populated by dissociative recombination of HeAr⁺, that Ar⁺² recombination mainly produces Ar(4s) states, and that electroionization from Ar metastables at moderate to high pump rates contributes to high efficiency, with experimental comparison indicating optimal Ar mole fractions of 0.1–5 % for quasicontinuous pumping.

Abstract

The high-pressure (≥0.5 atm) atomic Ar laser (3d→4p) oscillates on four infrared transitions (1.27–2.4 μm). Quasicontinuous oscillation on the 1.79 μm transition has been obtained using electron beam and fission-fragment excitation over a wide range of power deposition and gas pressure. In this regard, a computer model has been developed to investigate excitation mechanisms of the Ar laser. Results from the model suggest that the upper laser level of the 1.79 μm transition [Ar(3d[1/2]1)] is dominantly populated by dissociative recombination of HeAr+. In contrast, the dissociative recombination of Ar+2 is believed to predominantly produce Ar(4s) states. Electroionization from Ar metastables at moderate to high pump rates is likely to be responsible for the high efficiency of the Ar laser. Gain and laser oscillation are discussed and compared to experiments for He/Ar gas mixtures using various Ar mole fractions and total pressures. These results show that the optimum Ar mole fractions in He/Ar mixtures are ∼0.1%–5% for quasicontinuous pumping.