Focused fields of ultrashort radially-polarized laser pulses having low-order spatio-temporal couplings

TL;DR

This paper investigates the propagation and focusing properties of ultrashort radially-polarized laser beams with low-order spatio-temporal couplings, revealing unique control possibilities for strong-field applications.

Contribution

It introduces a detailed analysis of low-order spatio-temporal couplings in ultrashort RPLBs and compares their effects to linearly polarized beams, highlighting new control avenues.

Findings

Distinct focusing behaviors due to STCs

Comparison between radially-polarized and linearly polarized beams

Potential for advanced particle manipulation

Abstract

We present a detailed study of the fields and propagation characteristics around the focus of ultrashort radially-polarized laser beams (RPLBs) having low-order spatio-temporal couplings (STCs). The three STCs considered are the focusing of the different frequencies to different positions along the longitudinal coordinate, the focusing of the frequencies to different positions along one transverse coordinate, and the beam waist or Rayleigh range having a power-law frequency dependence. The STCs considered are deemed low-order because they are generally linear in frequency. The combination of a low-order vector beam, ultrashort pulse duration, and the three different STCs shows promise for exotic applications in dielectric or charged particle manipulation and potentially other strong-field phenomena. The STCs presented are all developed in a standard frequency-domain model where each case involves a different chromatic term. We present the results unique to the vector nature of the RPLBs and compare them to the linearly polarized cases, opening up opportunities for control of the electric field around the focus with the additional element of polarization.