Orbital Angular Momentum in Optics

Light carries not only energy and linear momentum but also angular momentum, and a subset of that — orbital angular momentum — arises when a beam's phase twists helically around its axis, forming a characteristic ring-shaped intensity profile. Controlling and transferring this property to matter has enabled precise rotation and trapping of microscopic objects using optical tweezers, sorting of particles in microfluidic systems, and the encoding of information in quantum communication protocols where each helical mode represents a distinct channel. Researchers are now pushing these techniques to the nanoscale through plasmonic structures that confine and enhance optical forces far below the diffraction limit, while also probing how spin and orbital degrees of freedom of light couple and exchange under tightly focused or structured illumination. Open questions center on how to generate and detect high-order orbital angular momentum states with high fidelity in noisy environments, and how to translate laboratory demonstrations into robust, integrated devices.

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Keywords

Optical ManipulationOrbital Angular MomentumLight BeamsOptical TweezersStructured LightPlasmonic Nano-optical Tweezers