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arXiv · 2609.25629

Orbital Optical Chirality as the Origin of Vortex Dichroism

Yoshito Y. Tanaka·Keiji Sasaki
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Abstract

Optical chirality quantifies the geometrical twisting of electromagnetic fields and underlies chiral light-matter interactions, yet its conventional formulation captures only the spin-associated chiral geometry of light. We introduce orbital optical chirality and derive its continuity equation, revealing physical properties distinct from those of angular momentum. For vortex beams, spin and orbital optical chiralities follow the spin and orbital indices, respectively. Applied to a twisted nanorod dimer, orbital optical chirality gives rise to vortex dichroism through quadrupolar hybridized modes, while dipolar modes exhibit only circular dichroism. These results establish a unified framework for optical chirality and provide access to chiral geometries beyond those resolved by spin optical chirality alone.

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Yoshito Y. Tanaka, Keiji Sasaki. 2026-09-22. Orbital Optical Chirality as the Origin of Vortex Dichroism. https://arxiv.org/abs/2609.25629

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