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Proceedings Paper

Universal spin-momentum locking of light (Conference Presentation)
Author(s): Todd Van Mechelen; Farid Kalhor; Ward D. newman; Zubin Jacob

Paper Abstract

We show the existence of an inherent property of evanescent electromagnetic waves: spin-momentum locking, where the direction of momentum fundamentally locks the polarization of the wave. We trace the ultimate origin of this phenomenon to complex dispersion and causality requirements on evanescent waves. We demonstrate that every case of evanescent waves in total internal reflection, surface states and optical fibers/waveguides possesses this intrinsic spin-momentum locking. We also introduce a universal right-handed triplet consisting of momentum, decay and spin for evanescent waves. We derive the Stokes parameters for evanescent waves which reveal an intriguing result - every fast decaying evanescent wave is inherently circularly polarized with its handedness tied to the direction of propagation. We also show the existence of a fundamental angle associated with total internal reflection (TIR) such that propagating waves locally inherit perfect circular polarized characteristics from the evanescent wave. This circular TIR condition occurs if and only if the ratio of permittivities of the two dielectric media exceeds the golden ratio. Our work leads to a unified understanding of this spin-momentum locking in various nanophotonic experiments and sheds light on the electromagnetic analogy with the quantum spin hall state for electrons.

Paper Details

Date Published: 21 September 2017
Proc. SPIE 10343, Metamaterials, Metadevices, and Metasystems 2017, 1034303 (21 September 2017); doi: 10.1117/12.2274897
Show Author Affiliations
Todd Van Mechelen, Purdue Univ. (United States)
Farid Kalhor, Purdue Univ. (United States)
Ward D. newman, Purdue Univ. (United States)
Zubin Jacob, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 10343:
Metamaterials, Metadevices, and Metasystems 2017
Nader Engheta; Mikhail A. Noginov; Nikolay I. Zheludev, Editor(s)

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