Near-resonant Raman amplification in the rotational quantum wavepackets of nitrogen molecular ions generated by strong field ionization

TL;DR

This study demonstrates near-resonant Raman amplification in nitrogen molecular ions' rotational wavepackets generated by strong mid-infrared femtosecond laser fields, revealing mechanisms for atmospheric lasing applications.

Contribution

It provides experimental evidence of stimulated Raman amplification in nitrogen ions' rotational wavepackets under near-resonant conditions, advancing understanding of strong field induced lasing.

Findings

Efficient conversion of broadband pulses into narrowband laser-like emissions.

Observation of stimulated Raman amplification in nitrogen molecular ions.

Insight into physical mechanisms of atmospheric lasing phenomena.

Abstract

Generation of laser-like narrow bandwidth emissions from nitrogen molecular ions generated in intense near- and mid-infrared femtosecond laser fields has aroused much interest because of the mysterious physics underlying such a phenomenon as well as the potential application of such an effect in atmospheric spectroscopic sensing. Here, we perform a pump-probe measurement on the nonlinear interaction of rotational quantum wavepackets of nitrogen molecular ions generated in mid-infrared (e.g., at a wavelength centered at 1580 nm) femtosecond laser fields with an ultrashort probe pulse whose broad spectrum overlaps both P- and R-branch rotational transition lines between the upper and lower electronic states. The results show that in the near-resonant conditions, stimulated Raman amplification can efficiently occur which converts the broad bandwidth ultrashort probe pulse into the narrow bandwidth laser-like beam. Our finding provides an insight into the physical mechanism of strong field induced lasing actions in atmospheric environment.