2026-10-13T04:36:48Z https://api.figshare.com/v2/oai

oai:figshare.com:article/34046811 2026-10-01T16:00:35Z category_37476 portal_1023 item_type_12 month_year_10_2026

Asymmetric imaging: Reciprocity bounds and manifestations Romil Audhkhasi (17434962) Anna Wirth-Singh (14366190) Rose Johnson (9641113) Maksym Zhelyeznyakov (14381925) Vladimir Yarmolik (25157313) Rafael Piestun (1982923) Andrea Alù (3960353) Arka Majumdar (1400788) Owen Miller (7381400) Physics (arXiv) physics.optics (arXiv) physics.app-ph (arXiv) Recent demonstrations of unidirectional imaging using diffractive multilayers have brought a concept akin to optical isolation to imaging, yet the fundamental limits of such asymmetry have remained unknown. Here we develop a general theory of asymmetric imaging in linear, passive, reciprocal optical systems and derive a fundamental bound on the achievable unidirectionality. Reciprocity requires the forward and reverse transmission operators to have identical singular values, a wave-optical analogue of étendue equality, with a simple consequence: perfect asymmetry is attainable only for sets of $M \leq N/2$ orthogonal object patterns, where $N$ is the number of available object/image modes; for $M > N/2$, the average power asymmetry is bounded by $(N-M)/M$. Guided by this result, we present two complementary realizations: refractive imaging systems formed by bulk lenses and stops that attain the half-occupation limit, and a 1 cm-diameter all-silicon metasurface doublet that exhibits asymmetric focusing at 4 $μ$m while fully complying with Lorentz reciprocity. We fabricate the doublet by direct laser writing and experimentally demonstrate its focusing asymmetry. By establishing mechanism-independent limits, our results provide a benchmark and design principle for asymmetric imaging across platforms, with implications for defense, surveillance and secure communications. 2026-09-28T00:00:00Z Text Preprint 10.48550/arXiv.2609.36350 https://figshare.com/articles/preprint/Asymmetric_imaging_Reciprocity_bounds_and_manifestations/34046811 CC0