Simple computer program to calculate arbitrary tightly focused (propagating and evanescent) vector light fields

Abstract

In this work we present a simple code to calculate tightly focused vectorial light fields (propagating and evanescent) generated by input fields that have arbitrary amplitude, phase and polarization. The program considers results from previous studies, like integration via fast Fourier transforms to speed up the integration. The calculations are done in a Cartesian coordinate system that is convenient to compare with experimental results for beams that are shaped with programmable optical elements like spatial light modulators or digital micromirror arrays. We also discuss how to avoid diverging terms at the origin by shifting the angular mesh by half a point and correcting the output by cancelling the phase term that arises from the shifted Fourier transform.