Hollow Gaussian beam generation through nonlinear interaction of photons with orbital-angular-momemtum

TL;DR

This paper introduces a novel method to generate Hollow Gaussian Beams (HGBs) using nonlinear three-wave mixing, enabling high-order, ultrafast HGBs with potential for broad wavelength and timescale applications.

Contribution

The authors demonstrate a new nonlinear optical technique for generating high-order HGBs, expanding the methods beyond traditional linear optical elements.

Findings

Successfully generated HGBs up to order 6 with >180 mW power at 355 nm.

Proposed a unique method to characterize the order of HGBs.

Showed that removing azimuthal phase from vortices does not produce Gaussian beams.

Abstract

Hollow Gaussian beams (HGB) are a special class of doughnut shaped beams that do not carry orbital angular momentum (OAM). Such beams have a wide range of applications in many fields including atomic optics, bio-photonics, atmospheric science, and plasma physics. Till date, these beams have been generated using linear optical elements. Here, we show a new way of generating HGBs by three-wave mixing in a nonlinear crystal. Based on nonlinear interaction of photons having OAM and conservation of OAM in nonlinear processes, we experimentally generated ultrafast HGBs of order as high as 6 and power >180 mW at 355 nm. This generic concept can be extended to any wavelength, timescales (continuous-wave and ultrafast) and any orders. We show that the removal of azimuthal phase of vortices does not produce Gaussian beam. We also propose a new and only method to characterize the order of the HGBs.