Collisional lasing on a self-terminating transition 2 1Po1 — 2 1S0 in helium atom

Abstract

Lasing on a self-terminating transition 2 1Po1 — 2 1S0 (λ = 2.058 μm) in helium atom is studied for a single- and double-pulse operation regimes under electron beam pumping in pure helium and its mixtures with H2, N2, O2, CO2, H2O, NH3, and N2O. In pure helium, the maximal pulse duration is ∼50 ns, which agrees with the calculated value. Recovery of lasing in the second pulse is observed at a time delay between the pulses of longer than 1.25 μs. In adding CO2, N2O, NH3, and H2O, the relaxation rate for population of the metastable state He(2 1S0) increases, which makes the delay, needed for recovering lasing, shorter up to pulse merging in the case of H2O. At the exciting pulse base-level duration of 1.2 μs, in mixtures of helium with NH3 and H2O, laser pulses with a duration of ∼0.8 μs are observed, which testifies that collisional quasi-cw lasing occurs. Mechanisms of collisional lasing are discussed.