Central frequency of few-cycle laser pulses in strong-field processes

TL;DR

This paper investigates how the difference between the central frequencies of the vector potential and electric field in few-cycle laser pulses affects strong-field processes, emphasizing the importance of accounting for this shift in simulations.

Contribution

It provides an analytical estimate of the frequency shift and highlights its impact on light-induced processes, improving the accuracy of modeling in strong-field physics.

Findings

Frequency shift influences excitation, ionization, and high harmonic generation.

Ignoring the shift can lead to misinterpretation of numerical results.

The paper offers a method to account for the frequency shift in simulations.

Abstract

We analyze the role of the difference between the central frequencies of the spectral distributions of the vector potential and the electric field of a short laser pulse. The frequency shift arises when the electric field is determined as the derivative of the vector potential to ensure that both quantities vanish at the beginning and end of the pulse. We derive an analytical estimate of the frequency shift and show how it affects various light induced processes, such as excitation, ionization and high harmonic generation. Since observables depend on the frequency spectrum of the electric field, the shift should be taken into account when setting the central frequency of the vector potential to avoid potential misinterpretation of numerical results for processes induced by few-cycle pulses.