Controlling the Bandwidth of High Harmonic Emission Peaks with the Spectral Polarization of the Driver

TL;DR

This paper presents a novel high-harmonic generation method that controls spectral peak bandwidth using spectral polarization of a two-color driver, enabling broad, tunable, high-flux EUV radiation for advanced spectroscopy.

Contribution

It introduces a new HHG scheme utilizing a vectorial two-color driver with spectral polarization control to tune the bandwidth of emission peaks.

Findings

Bandwidth of spectral peaks is proportional to the frequency difference between colors.

Supercontinuum generation achieved through peak broadening.

The method produces high-flux broadband EUV radiation suitable for attosecond spectroscopy.

Abstract

We demonstrate a High-Harmonic-Generation scheme which offers control over the bandwidth of the spectral peaks. The scheme uses a vectorial two-color driver with close central frequencies, generated by spectrally splitting a linearly-polarized input femtosecond-duration laser pulse and subsequent recombining the two halves after their polarizations are made cross-elliptical and counter-rotating. This results in the generation of new emission channels which coalesce into broad odd-integer HHG peaks, the bandwidth of each being proportional to the frequency difference between the two colors, to the harmonic order and inversely-proportional to the driver fields' ellipticities. Peak-broadening to the extent that a supercontinuum is formed is also demonstrated. This source will find use in HHG applications benefiting from high-flux broadband extreme ultra-violet radiation, such as attosecond transient absorption spectroscopy.