Substrate-induced maximum optical chirality of planar dielectric structures

Gorkunov, Maxim V., Antonov, Alexander A., Mamonova, Alena V., Muljarov, Egor A. ORCID: https://orcid.org/0000-0002-2878-4148 and Kivshar, Yuri 2024. Substrate-induced maximum optical chirality of planar dielectric structures. Advanced Optical Materials , 2402133. 10.1002/adom.202402133 Item availability restricted.

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Abstract

Resonant dielectric planar structures can interact selectively with light of particular helicity thus providing an attractive platform for chiral flat optics. The absence of mirror-symmetry planes defines geometric chirality, and it remains the main condition for achieving strong circular dichroism. For planar optical structures such as photonic-crystal slabs and metasurfaces, breaking the out-of-plane mirror symmetry is especially challenging, as it requires to fabricate meta-atoms with a tilt, variable height, or vertically shifted positions. Although transparent substrates formally break out-of-plane mirror symmetries, their optical effect is typically subtle being rarely considered for enhancing optical chirality. Here it is revealed that low-refractive-index substrates can induce up to maximum intrinsic optical chirality in otherwise achiral metastructures so that the transparency to waves of one helicity is combined with resonant blocking of waves of the opposite helicity. This effect originates from engineering twisted photonic eigenstates of different parities. The perturbation analysis developed in terms of the resonant-state expansion reveals how the eigenstate coupling induced by a substrate gives rise to a pair of chiral resonances of opposite handedness. The general theory is confirmed by the specific examples of light transmission in the normal and oblique directions by a rotation-symmetric photonic-crystal slab placed on different transparent substrates.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Physics and Astronomy
Publisher:	Wiley
ISSN:	2195-1071
Date of First Compliant Deposit:	14 November 2024
Date of Acceptance:	11 October 2024
Last Modified:	10 Dec 2024 11:30
URI:	https://orca.cardiff.ac.uk/id/eprint/174008

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