Attosecond spectroscopy using vacuum-ultraviolet pulses emitted from laser-driven semiconductors

TL;DR

This paper demonstrates the generation of attosecond pulses from laser-driven semiconductors using high harmonic generation, enabling ultrafast spectroscopy of low ionization potential systems and advancing attosecond science.

Contribution

It introduces a novel method to produce attosecond pulses via high harmonics from ZnO crystals, expanding the spectral range for ultrafast spectroscopy and potential quantum light sources.

Findings

Attosecond pulses generated from ZnO via high harmonic generation.

VUV high harmonics used to probe ultrafast ionization dynamics.

Phase oscillations encode attosecond pulse synchronization.

Abstract

Strongly laser-driven semiconductor crystals offer substantial advantages for the study of many-body physics and ultrafast optoelectronics via the high harmonic generation process. While this phenomenon has been employed to investigate the dynamics of solids in the presence of strong laser fields, its potential to be utilized as an attosecond light source has remained unexploited. Here, we demonstrate that the high harmonics generated through the interaction of mid--infrared pulses with a ZnO crystal leads to the production of attosecond pulses, that can be used to trace the ultrafast ionization dynamics of alkali metals. In a cross--correlation approach, we photoionize Cesium atoms with the vacuum-ultraviolet (VUV) high-harmonics in the presence of a mid-infrared laser field. We observe strong oscillations of the photoelectron yield originating from the instantaneous polarization of the atoms by the laser field. The phase of the oscillations encodes the attosecond synchronization of the ionizing high-harmonics and is used for attosecond pulse metrology. This light source opens a new spectral window for attosecond spectroscopy, paving the way for studies of systems with low ionization potentials including neutral atoms, molecules and solids. Additionally, our results highlight the significance of the source for generating non--classical massively entangled light states in the visible--VUV spectral region.