Spectral intensity and phase changes of short laser pulses by two-photon absorption

TL;DR

This paper models how two-photon absorption affects the spectral intensity and phase of short laser pulses passing through a molecular medium, considering molecular decay and pulse chirp effects.

Contribution

It introduces a calculation of third order non-linear polarization to analyze spectral and phase changes in laser pulses due to two-photon absorption in a dielectric medium.

Findings

Spectral intensity and phase are significantly altered by two-photon absorption.

Molecular decay rate influences the extent of spectral and phase modifications.

Pulse chirp impacts the spectral and phase changes during propagation.

Abstract

We calculated third order non-linear polarization to estimate the two-photon absorption of non-interacting two-level molecules in the transmission-type degenerate pump-probe geometry. The spectral intensity and the phase changes of the laser pulses when passing through a thin dielectric slab composed of the molecules were considered. We also investigated the effect of the decay rate of the molecules and the chirp of the pulses on their spectral intensity and phase changes.