Enforcing energy balance in coherently superimposed optical vortices

TL;DR

This paper analyzes the energy distribution in coherent superpositions of optical vortices and proposes a design method for phase gratings that ensures uniform energy distribution among OAM modes while reducing high radial modes.

Contribution

It introduces a novel design approach for phase gratings that enforces energy balance among OAM modes in coherent optical vortex beams.

Findings

Unequal energy distribution from standard LG mode-based gratings.

Adjusting beam width does not correct energy imbalance.

New design method achieves uniform energy distribution and minimizes high radial modes.

Abstract

The generation of optical beams with multiple, mutually-coherent orbital-angular-momentum (OAM) modes using phase gratings is analyzed from the perspective of energy distribution and radial mode composition. We show that phase gratings designed with equally-weighted Laguerre-Gauss (LG) modes will generate beams with uneven energy distribution among OAM components. This unwanted outcome cannot be corrected by adjusting the width of the illuminating beam. We propose a way to design phase gratings that will produce a uniform energy distribution among the constituent OAM states after illumination, while minimizing the content of high radial modes. This method is based on a generalized definition for the LG modes that takes advantage of the freedom to select their radial scales.