Vortex-Free Intrinsic Orbital Angular Momentum

Abstract

Optical orbital angular momentum (OAM) has traditionally relied on vortex beams with helical phase fronts imparting quantized intrinsic OAM. Here, we introduce a fundamentally vortex_free framework where intrinsic OAM arises from the natural curvature of lights energy flow, specifically, the caustic geometry of self_accelerating beams whose curved trajectories act as orbital highways for photons. This OAM generation mechanism is independent of phase vortices but mirrors celestial orbital motion. Through numerical simulations, experimental characterization, and optomechanical measurements using optical tweezers, we demonstrate intrinsic vortex_free OAM rooted solely in beam intensity architecture. Generalizing beyond geometric caustics to arbitrary optical fields, we demonstrate OAM via curved Poynting_vector energy streamlines, unifying conventional vortex and novel vortex_free OAM under a single quantitative framework. Streamline engineering enables customizable rotational dynamics, including hybrid orbital_cyclonic motions reminiscent of tropical storms, with promising applications in precision optomechanics, optofluidics, and optical analogues of fluid dynamics. This energy-flow perspective offers a versatile platform for designing and quantifying OAM across structured light.