Abstract
We experimentally demonstrate the existence of long-lived coherent polarizations coupling simultaneously ground state X (X2Σg+) to excited states A (A2Πu) and B (B2Σu+) of N2+ inside a plasma created by a short intense laser pulse at 800 nm. This three-level V-scheme arrangement is responsible for a strong optical gain without population inversion at the B–X transition at 391.4 nm. Simulations based on Maxwell-Bloch equations reproduce well the kinetics and the pressure dependence of the gain.
Highlights
When two electronic levels ∣1⟩ and ∣2⟩ in an atomic or molecular system are simultaneously coupled by two coherent light fields to a common level ∣3⟩, the corresponding amplitudes of transition probability can interfere
We experimentally demonstrate the existence of long-lived coherent polarizations coupling simultaneously ground state X (X2Σ+g ) to excited states A (A2Πu) and B (B2Σ+u) of N+2 inside a plasma created by a short intense laser pulse at 800 nm
We report on the occurrence of such a lasing without population inversion in a weakly ionized gas of nitrogen molecules
Summary
When two electronic levels ∣1⟩ and ∣2⟩ in an atomic or molecular system are simultaneously coupled by two coherent light fields to a common level ∣3⟩, the corresponding amplitudes of transition probability can interfere. We experimentally demonstrate the existence of long-lived coherent polarizations coupling simultaneously ground state X (X2Σ+g ) to excited states A (A2Πu) and B (B2Σ+u) of N+2 inside a plasma created by a short intense laser pulse at 800 nm.
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