Fields of an ultrashort tightly-focused laser pulse

TL;DR

This paper derives accurate electromagnetic field expressions for ultrashort, tightly focused laser pulses in vacuum, highlighting the importance of scalar potential and envelope effects on laser-matter interactions.

Contribution

It introduces a new analytic method for modeling laser fields that improves accuracy in the subcycle pulse regime compared to existing approaches.

Findings

Derived well-behaved, accurate field expressions

Compared with Lax series and complex-source approaches

Identified significant effects of scalar potential and envelope

Abstract

Analytic expressions for the electromagnetic fields of an ultrashort, tightly focused, linearly polarized laser pulse in vacuum are derived from scalar and vector potentials, using a small parameter which assumes a small bandwidth of the laser pulse. The derived fields are compared with those of the Lax series expansion and the complex-source-point approaches and are shown to be well-behaved and accurate even in the subcycle pulse regime. We further demonstrate that terms stemming from the scalar potential and due to a fast varying pulse envelope are non-negligible and may significantly influence laser-matter interactions.