Structured squeezed light allows for high-harmonic generation in classical forbidden geometries

TL;DR

This paper demonstrates that non-classical structured light, specifically squeezed circularly polarized light, can enable high-harmonic generation in geometries where classical light cannot, by modifying electron dynamics and the HHG process.

Contribution

The study introduces the use of non-classical squeezed light to enable HHG in forbidden geometries, linking quantum optical features to electron dynamics and harmonic generation.

Findings

Squeezed light enables HHG in circular polarization configurations that are classically forbidden.

The spectral properties of harmonics depend on the type of squeezing applied.

Modifications in the three-step HHG mechanism are related to the squeezing type.

Abstract

High-harmonic generation (HHG) is a nonlinear process in which a strong driving field interacts with a material, resulting in the frequency up-conversion of the driver into its high-order harmonics. This process is highly sensitive to the field's polarization: circular polarization, for instance, inhibits HHG. In this work, we demonstrate that the use of non-classical structured light enables HHG in this otherwise prohibitive configuration for classical drivers. We consider circularly polarized light with non-classical fluctuations, introduced via squeezing along one polarization direction, and show that these non-classical features prompt the HHG process. We find that the spectral properties of the emitted harmonics depend on the type of squeezing applied and, by analyzing the inner electron dynamics, we relate the observed differences to modifications of the HHG three-step mechanism induced by the specific squeezing type. This approach opens new pathways for integrating quantum optics in HHG, providing novel means of controlling the light-matter interaction dynamics.