Truncated triangular diffraction lattices and orbital-angular-momentum detection of vortex SU(2) geometric modes

TL;DR

This paper introduces a novel method using truncated triangular diffraction lattices to detect and analyze the complex orbital angular momentum of SU(2) vortex modes, expanding capabilities in topological beam characterization.

Contribution

It presents the first experimental demonstration of truncated diffraction with a triangular aperture for SU(2) modes and a new approach to measure their OAM and topological charge.

Findings

Truncated triangular diffraction patterns reveal exotic intensity and OAM distributions.

A meshy structure in the diffraction pattern allows evaluation of partial topological charge.

Adjusting aperture size and position enables classical spot-array lattice measurement of OAM.

Abstract

We for the first time report the truncated diffraction with a triangular aperture of the SU(2) geometric modes and propose a method to detect the complicated orbital angular momentum (OAM) of an SU(2) wave-packet, to the best of our knowledge. As a special vortex beam, a nonplanar SU(2) mode carrying special intensity and OAM distributions brings exotic patterns in truncated diffraction lattice. A meshy structure is unveiled therein by adjusting the illuminated aperture in vicinity of the partial OAM regions, which can be elaborately used to evaluate the partial topological charge and OAM of an SU(2) wave-packet by counting the dark holes in the mesh. Moreover, through controlling the size and position of the aperture at the center region, the truncated triangular lattice can be close to the classical spot-array lattice for measuring the center OAM. These effects being fully validated by theoretical simulations greatly extend the versatility of topological structures detection of special beams.