Linking High-Harmonic Generation and Strong-Field Ionization in Bulk Crystals

TL;DR

This paper demonstrates a clear link between high-harmonic generation and laser-induced ionization in bulk crystals, advancing understanding of nonlinear optical phenomena in solids through combined experimental and theoretical approaches.

Contribution

It provides the first unambiguous experimental correlation between high-harmonic emission and ionization in solids, supported by numerical and theoretical modeling.

Findings

Confirmed correlation between harmonic emission and ionization

Demonstrated angular dependence of nonlinear absorption and harmonic generation

Supported results with semiconductor Bloch equations and Wannier-function calculations

Abstract

The generation of high-order harmonics in bulk solids subjected to intense ultrashort laser pulses has opened up new avenues for research in extreme nonlinear optics and light-matter interaction on sub-cycle timescales. Despite significant advancement over the past decade, a complete understanding of the involved phenomena is still lacking. High-harmonic generation in solids is currently understood as arising from nonlinear intraband currents, interband recollision and ionization-related phenomena. As all of these mechanisms involve or rely upon laser-driven excitation we combine measurements of the angular dependence of nonlinear absorption and high-order harmonic generation in bulk crystals to demonstrate the relation between high-harmonic emission and nonlinear, laser-induced ionization in solids. An unambiguous correlation between the emission of harmonics and laser-induced ionization is found experimentally, that is supported by numerical solutions of the semiconductor Bloch equations and calculations of orientation-dependent ionization rates using maximally localized Wannier-functions.