Planar chiral metasurfaces with maximal and tunable chiroptical response driven by bound states in the continuum

Tan Shi, Zi Lan Deng, Guangzhou Geng, Xianzhi Zeng, Yixuan Zeng, Guangwei Hu, Adam Overvig, Junjie Li, Cheng Wei Qiu, Andrea Alù, Yuri S. Kivshar, Xiangping Li

Research output: Contribution to journalArticlepeer-review

243 Scopus citations

Abstract

Optical metasurfaces with high quality factors (Q-factors) of chiral resonances can boost substantially light-matter interaction for various applications of chiral response in ultrathin, active, and nonlinear metadevices. However, current approaches lack the flexibility to enhance and tune the chirality and Q-factor simultaneously. Here, we suggest a design of chiral metasurface supporting bound state in the continuum (BIC) and demonstrate experimentally chiroptical responses with ultra-high Q-factors and near-perfect circular dichroism (CD = 0.93) at optical frequencies. We employ the symmetry-reduced meta-atoms with high birefringence supporting winding elliptical eigenstate polarizations with opposite helicity. It provides a convenient way for achieving the maximal planar chirality tuned by either breaking in-plane structure symmetry or changing illumination angle. Beyond linear CD, we also achieved strong near-field enhancement CD and near-unitary nonlinear CD in the same planar chiral metasurface design with circular eigen-polarization. Sharply resonant chirality realized in planar metasurfaces promises various practical applications including chiral lasers and chiral nonlinear filters.

Original languageEnglish
Article number4111
JournalNature Communications
Volume13
Issue number1
DOIs
StatePublished - Dec 2022

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