Energetic, tunable, highly-elliptically polarized higher harmonics generated by intense two-color counter rotating laser fields

TL;DR

This paper demonstrates the experimental generation of highly-elliptical, tunable high-harmonics in argon gas driven by two-color counter rotating laser fields, with simulations confirming the robustness and tunability of the process.

Contribution

It introduces a method to generate energetic, highly-elliptical, and tunable high-harmonics using bichromatic fields, surpassing many existing sources in energy output.

Findings

High-harmonic spectra tunable over ~150 meV

Energy per pulse of ~400 nJ in the XUV range

Robustness of HHG confirmed by density functional simulations

Abstract

In this work, we demonstrate experimentally the efficient generation and tunability of energetic highly-elliptical high-harmonics in Ar gas, driven by intense two-color counter rotating laser electric fields. A bi-chromatic beam tailored by a MAZEL-TOV apparatus generates HHG, where the output spectrum of the highly elliptical HHG radiation can be tuned for a energy range of \DeltaE\HF150meV in the spectral range of ~20 eV with energy per pulse EXUV~400 nJ at the source. Furthermore we employ time-dependent density functional simulations to probe in-depth the dependence of the harmonic ellipticity and the strength of the isolated atto pulses on the driving field parameters and demonstrate the robustness of the HHG with the bichromatic field. We show how by properly tuning the central frequency of the second harmonic, the central frequency of the extreme ultraviolet (XUV) high harmonic radiation is continuously tuned. The demonstrated energy values largely exceed the output energy from many other laser driven attosecond sources reported so far and prove to be sufficient for inducing (along with tight XUV focusing geometries) the nonlinear processes in the atomic system. We envisage that such tunable energetic highly-elliptical HHG spectra can remove the facility restrictions from requirements of few-cycle driving pulses for isolated circular attosecond pulse generation.