Polarisation control of quasi-monochromatic XUV produced via resonant high harmonic generation

TL;DR

This paper investigates how resonant high harmonic generation in tin ions can be controlled to produce quasi-monochromatic XUV light with adjustable polarization, revealing unique behaviors of harmonic yield and polarization near resonance.

Contribution

It introduces a numerical and analytical study of resonant HHG in tin ions, highlighting the anomalous ellipticity dependence and polarization properties of generated harmonics.

Findings

Resonant harmonic yield decreases slowly with ellipticity, unlike nonresonant harmonics.

Harmonics near resonance exhibit higher ellipticity than off-resonance harmonics.

Potential to generate tunable, quasi-monochromatic, circularly polarized XUV light.

Abstract

We present a numerical study of the resonant high harmonic generation by tin ions in an elliptically-polarised laser field along with a simple analytical model revealing the mechanism and main features of this process. We show that the yield of the resonant harmonics behaves anomalously with the fundamental field ellipticity, namely the drop of the resonant harmonic intensity with the fundamental ellipticity is much slower than for high harmonics generated through the nonresonant mechanism. Moreover, we study the polarisation properties of high harmonics generated in elliptically-polarised field and show that the ellipticity of harmonics near the resonance is significantly higher than for ones far off the resonance. This introduces a prospective way to create a source of the quasi-monochromatic coherent XUV with controllable ellipticity potentially up to circular.