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arXiv · 2604.10001

Nonlocal current-response theory of structured-light dichroism

Akihito Kato·Nobuhiko Yokoshi
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Abstract

We develop a nonlocal minimal-coupling theory of structured-light dichroism. Optical absorption is written as a bilinear functional of the incident vector potential and the nonlocal current-response kernel, retaining the spatial structure of optical vortex beams and other inhomogeneous fields. Circular dichroism, helical dichroism, and helical circular dichroism are treated as distinct reversal channels that project different reversal-odd components of the same microscopic response. The resulting signal is resolved into symmetry, tensor, and angular-mode sectors. Single azimuthal-mode fields probe diagonal OAM-channel components, whereas mixed modes access off-diagonal mode-space coherence through interference between different OAM channels. The relative polarization of the mixed field further selects scalar, axial-vector, or rank-2 tensor sectors of the response. This decomposition gives selection rules for high-symmetry systems and a diagnostic scheme for low-symmetry nanophotonic structures, finite systems, and extended materials, where several angular-channel responses may coexist. It also connects the nonlocal current-response formulation to local-gradient descriptions based on spatial dispersion, optical chirality, and tensorial anisotropy.

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Akihito Kato, Nobuhiko Yokoshi. 2026-04-11. Nonlocal current-response theory of structured-light dichroism. https://doi.org/10.1103/xnw4-pm1p

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