Fields of an ultrashort tightly focused radially polarized laser pulse in a linear response plasma

TL;DR

This paper derives analytic expressions for the electromagnetic fields of an ultrashort, tightly focused radially polarized laser pulse in a linear plasma, improving modeling accuracy over traditional paraxial approximations.

Contribution

It provides a novel analytical framework for describing laser pulse fields in plasma, surpassing the accuracy of common paraxial models.

Findings

Zeroth-order axial electric field models pulse better than paraxial approximation.

Derived fields exhibit correct vacuum limits.

Propagation characteristics are discussed and validated.

Abstract

Analytic expressions for the fields of a radially polarized, ultrashort and tightly focused laser pulse propagating in a linear-response plasma are derived and discussed. The fields are obtained from solving the inhomogenous wave equations for the vector and scalar potentials, linked by the Lorenz gauge, in a plasma background. First the scalar potential is eliminated using the gauge condition, then the vector potential is synthesized from Fourier components of an initial uniform distribution of wavenumbers, and the inverse Fourier transformation is carried out term-by-term in a truncated series (finite sum). The zeroth-order term in, for example, the axial electric field component is shown to model a pulse much better than its widely used paraxial approximation counterpart. Some of the propagation characteristics of the fields are discussed and all fields are shown to have manifestly the expected limits for propagation in a vacuum.