Harmonic-seeded resonant Raman amplification in strong-field ionized nitrogen molecules

TL;DR

This paper demonstrates the generation of laser-like emissions in nitrogen molecules through resonant Raman amplification, combining nonlinear optical effects, with potential applications in remote sensing.

Contribution

It reveals the mechanism of laser-like emission generation via resonant Raman amplification of the fifth harmonic in nitrogen molecules under intense mid-infrared laser fields.

Findings

Laser-like emissions depend on laser wavelength and power.

Emission results from resonant Raman amplification in nitrogen ions.

The process involves both perturbative and non-perturbative effects.

Abstract

Generation of free-space laser-like emissions of high spatiotemporal coherence and narrow bandwidth in atmosphere opens promising opportunities for remote spectroscopic sensing. Here, we report on generation of such laser-like emissions, which results from the combined contributions of perturbative and non-perturbative nonlinear optical effects in nitrogen molecules exposed to intense mid-infrared laser fields. We systematically investigate the dependence of the generated free-space laser spectrum on wavelength and power of the driver laser. It is revealed that the free-space laser is produced by resonant Raman amplification of the fifth harmonic of the driver pulses in rotational wavepacket of the molecular nitrogen ions.