Evolution of topological charge in a triangular interference lattice

Abstract

Optical vortices can be generated periodically across an interference region when three or more coherent waves interact, forming an optical vortex array (OVA). In this work, we investigate how the initial topological charge (TC) of the incident beam is redistributed among the phase singularities formed in the interference field by interfering a Laguerre-Gaussian beam carrying orbital angular momentum (OAM) of ± l with two Gaussian beams, while the total TC remains constant. We demonstrate that, for a zero-order vortex beam (l = 0), the interference results in paired vortices carrying opposite unit TCs of ± 1, whereas for nonzero TCs (l > 0), the original TC does not remain localized in a single higher-order vortex but instead undergoes a systematic splitting into l individual unpaired vortices, each carrying a unit TC of + 1. For fractional TC, the number of unpaired vortices follows a nearest integer rule of the imposed TC, exhibiting n unpaired vortices for fractional charges closer to the integer n and n + 1 unpaired vortices as the charge approaches the next higher integer. The reported results are supported by numerical simulations and experimental verification, providing new insight into optical vortex formation and enabling controlled vortex engineering with potential applications in optical trapping and manipulation, high-dimensional optical communication, and structured-light-based information encoding.