Bidirectional cascaded superfluorescent lasing in air enabled by resonant third harmonic photon exchange from nitrogen to argon

TL;DR

This paper uncovers a new mechanism for cavity-free atmospheric air lasing involving resonant energy transfer via third harmonic photons, enabling bidirectional cascaded superfluorescent lasing with potential remote sensing applications.

Contribution

It introduces a novel third harmonic photon exchange mechanism that facilitates cascaded superfluorescent lasing in air, distinct from previous ASE-based processes.

Findings

Demonstrated bidirectional two-color cascaded lasing in air.

Confirmed superfluorescence as the lasing mechanism.

Identified third harmonic photon exchange as the key process.

Abstract

Cavity-free lasing in atmospheric air has stimulated intense research towards fundamental understanding of underlying physical mechanisms. In this Letter, we identify a new mechanism -- third harmonic photon mediated resonant energy transfer pathway leading to population inversion in argon via initial three-photon excitation of nitrogen molecules irradiated by intense 261 nm pulses -- that enables bidirectional two-color cascaded lasing in atmospheric air. By making pump-probe measurements, we conclusively show that such cascaded lasing results from superfluorescence (SF) rather than amplified spontaneous emission (ASE). Such cascaded lasing with the capability of producing bidirectional multicolor coherent pulses opens additional possibilities for remote sensing applications.