Generation of elliptically polarized nitrogen-ion laser fields using two-color femtosecond laser pulses

TL;DR

This study demonstrates the generation of elliptically polarized nitrogen-ion laser fields by using two orthogonally polarized femtosecond laser pulses, revealing the role of birefringence in the gain medium.

Contribution

It introduces a method to produce elliptically polarized nitrogen-ion lasers through polarization control of two-color femtosecond pulses.

Findings

Elliptically polarized nitrogen-ion laser fields are generated.

Changing the polarization angle affects the laser's ellipticity.

Strong birefringence near the laser wavelength influences polarization.

Abstract

We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized molecular nitrogen-ion laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the molecular nitrogen-ion laser.