Suppression of individual peaks in two-colour high harmonic generation

TL;DR

This paper demonstrates how specific harmonic peaks can be selectively suppressed in high-harmonic spectra using tailored two-colour laser pulses, with suppression mechanisms explained by interference effects.

Contribution

It introduces a method to suppress individual harmonics in high-harmonic generation using symmetry-broken laser fields, supported by theoretical modeling.

Findings

Peak suppression is unique to symmetry-broken fields ($$-$2$).

Spectral interference between asymmetric half-cycles causes suppression.

Macroscopic and semi-classical calculations agree with experimental observations.

Abstract

This work investigates the suppression of individual harmonics, simultaneously affecting specific even and odd orders in the high-harmonic spectra generated by strongly tailored, two-colour, multi-cycle laser pulses in neon. The resulting spectra are systematically studied as a function of the electric-field shape in a symmetry-broken ($\omega$-$2\omega$) and symmetry-preserved ($\omega$-$3\omega$) configuration. The peak suppression is reproduced by macroscopic strong-field approximation calculations and is found to be unique to symmetry-broken fields ($\omega$-$2\omega$). Additionally, semi-classical calculations further corroborate the observation and reveal their underlying mechanism, where a nontrivial spectral interference between subsequent asymmetric half-cycles is found to be responsible for the suppression.