Coherence Enhanced Transient Lasing in XUV Regime

TL;DR

This paper demonstrates that applying a resonant coherent drive to a specific transition in a three-level system can significantly enhance transient lasing in the XUV and X-ray regimes, emphasizing the role of coherence in laser energy output.

Contribution

It introduces a method to enhance transient lasing energy in the XUV/X-ray regime using coherent driving, highlighting the importance of coherence in laser power enhancement.

Findings

Coherent drive on the $a\leftrightarrow c$ transition enhances laser energy output by an order of magnitude.

Coherence $\varrho_{ac}$ is crucial for laser power enhancement.

Coherent drive suppresses backward gain while potentially enhancing forward gain.

Abstract

We report the effect of a coherent drive on transient lasing in three-level $\Lambda $ and $\Xi$ configurations ($c\leftrightarrow a\leftrightarrow b$). We show that the presence of a resonant coherent drive on the $a\leftrightarrow c$ optical transition can yield an order of magnitude enhancement of the output laser energy on a $a\rightarrow b$ XUV or X-ray transition than with no coherent drive. We demonstrate the crucial role of coherence $\varrho_{ac}$ for the laser power enhancement. Contrary to the forward direction (with respect to the pump), where forward gain can be enhanced for some choice of the drive Rabi frequency $\Omega_{c}$, coherent drive on the $ac$ transition always suppresses the backward gain.