2D quantum-path interference in high-harmonic generation driven by highly-bichromatic fields

TL;DR

This paper reports the experimental observation of a novel 2D quantum-path interference in high-harmonic generation driven by orthogonally-polarized bichromatic fields, revealing complex harmonic modulation patterns and new spectroscopic possibilities.

Contribution

It introduces the first experimental demonstration of 2D-QPI in HHG driven by highly-bichromatic fields and analyzes the underlying quantum orbit contributions.

Findings

Odd harmonics show monomodal modulation behavior.

Even harmonics exhibit bimodal modulation structure.

Strong-field approximation calculations reveal symmetry inheritance in dipole response.

Abstract

We experimentally observe a new type of quantum-path interference, in two-dimensions (2D-QPI), in high-harmonic generation (HHG) driven by an orthogonally-polarised highly-bichromatic field. This regime is marked by comparable intensities of the two orthogonal colours. In this highly-bichromatic regime, we demonstrate that 2D-QPI is encoded in the measured harmonic intensity modulations with respect to the relative phase of the two-colour field. The modulations of the odd-order harmonics show a monomodal behaviour, whereas the even harmonics are modulated in a bimodal structure. Our calculations using the strong-field approximation and saddle-point method disentangle contributions from multiple quantum orbits in this HHG regime, revealing that the dipole response for both odd and even harmonics inherits the dynamic symmetry of the orthogonally-polarised driving field. This new type of 2D-QPI offers a novel route to HHG spectroscopy of attosecond electron dynamics by lifting up the dimensionality of the quantum paths involved in the interference.