A modal description of paraxial structured light propagation

TL;DR

This paper introduces a modal approach to paraxial light propagation that simplifies calculations, reduces numerical artifacts, and provides intuitive understanding, validated through theoretical comparison and experimental examples.

Contribution

It presents a novel modal decomposition method for paraxial light propagation that improves computational efficiency and interpretability over traditional angular spectrum techniques.

Findings

The modal approach reduces numerical artifacts compared to angular spectrum methods.

It allows fast and analytical propagation of complex fields.

Experimental validation confirms the method's accuracy and usefulness.

Abstract

Here we outline a description of paraxial light propagation from a modal perspective. By decomposing the initial transverse field into a spatial basis whose elements have known and analytical propagation characteristics, we are able to analytically propagate any desired field, making the calculation fast and easy. By selecting a basis other than that of planes waves, we overcome the problem of numerical artefacts in the angular spectrum approach and at the same time are able to offer an intuitive understanding for why certain classes of fields propagate as they do. We outline the concept theoretically, compare it to the numerical angular spectrum approach, and confirm its veracity experimentally using a range of instructive examples. We believe that this modal approach to propagating light will be a useful addition to toolbox for propagating optical fields.