Generating optical angular momentum through wavefront curvature

Forbes, Kayn A., Aita, Vittorio and Zayats, Anatoly V. (2025) Generating optical angular momentum through wavefront curvature. APL Photonics, 10 (2). ISSN 2378-0967

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Abstract

Recent developments in the understanding of optical angular momentum have resulted in many demonstrations of unusual optical phenomena, such as optical beams with orbital angular momentum and transverse spinning light. Here, we detail novel contributions to spin and orbital angular momentum generated by the wavefront curvature that becomes relevant in strongly focused beams of light. While circularly polarized beams are shown to develop helicity-dependent transverse spin, a linearly polarized Gaussian beam produces longitudinal spin and orbital angular momentum in the focal region, even if lacking both of these before focusing. An analytical treatment of a nonparaxial electromagnetic field, validated with vectorial diffraction modeling, shows that the terms related to higher orders of a paraxial parameter are responsible for the appearance of non-trivial angular momenta. The obtained dependences relate these quantities to the wavefront curvature, showing how it can be used as a novel degree of freedom for applications in optical manipulation and light–matter interactions at subwavelength scales, enabling angular momentum transfer even from a simple Gaussian beam with linear polarization.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
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Depositing User: LivePure Connector
Date Deposited: 04 Feb 2025 16:15
Last Modified: 17 Feb 2025 09:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/98367
DOI: 10.1063/5.0249700

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