Molecular alignment and filamentation: comparison between weak and strong field models

TL;DR

This study compares weak and strong field models of laser-induced molecular alignment to understand their effects on filamentation, revealing that weak field models are accurate for single pulses but fail with multiple pulses due to nonlinear interactions.

Contribution

It provides a detailed numerical comparison between weak and strong field models in the context of filamentation, highlighting the limitations of the weak field approximation in complex pulse scenarios.

Findings

Weak field model accurately reproduces single pulse filamentation dynamics.

Weak field model fails for intense pulses in the wake of a second pulse.

Discrepancies are maximal at delays of half the molecular rotational period.

Abstract

The impact of nonadiabatic laser-induced molecular alignment on filamentation is numerically studied. Weak and strong field model of impulsive molecular alignment are compared in the context of nonlinear pulse propagation. It is shown that the widely used weak field model describing the refractive index modification induced by impulsive molecular alignment accurately reproduces the propagation dynamics providing that only a single pulse is involved during the experiment. On the contrary, it fails at reproducing the nonlinear propagation experienced by an intense laser pulse traveling in the wake of a second strong laser pulse. The discrepancy depends on the relative delay between the two pulses and is maximal for delays corresponding to half the rotational period of the molecule.