Transition from multiphoton to tunneling ionization in the process of high harmonic generation in solids

TL;DR

This paper investigates the transition from multiphoton to tunneling ionization in high harmonic generation in solids, highlighting the importance of bandgap modification and power dependence in understanding the process.

Contribution

It provides a combined experimental and theoretical analysis of the power scale dependence, revealing a transition in the ionization mechanism during high harmonic generation in solids.

Findings

Power scale dependence divides the interaction into two regimes.

Bandgap modification by intense laser is crucial for accurate modeling.

Transition from multiphoton to tunneling ionization is observed.

Abstract

High harmonic generation in solids is becoming an important method for strong field solid state physics research. The power scale relationship between high harmonics and the driving laser is investigated both experimentally and theoretically. Results of the power scale dependence clearly divided the interaction into two regimes. The modification of the bandgap by intense laser proved to be very important for theoretically reproducing the experimental result. Combining with the Keldysh theory analysis, the harmonic generation process is found to be transitioned from multiphoton excitations to the diabatic tunneling.