Chiral nonlinear polaritonics with van der Waals metasurfaces.

Heimig, Connor; Antonov, Alexander A; Gryb, Dmytro; Possmayer, Thomas; Weber, Thomas; Hirler, Michael; Biechteler, Jonas; Sortino, Luca et al. · Sci Adv · 2026

basic_science · Level V

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Abstract

Chiral optical cavities are crucial for the development of nonequilibrium quantum materials by discriminating and selectively coupling to light of a specific circular polarization, but fundamentally cannot be realized with conventional mirror cavities. Here, we demonstrate this unique functionality by developing a monolithic transition metal dichalcogenide (TMDC) metasurface with broken out-of-plane symmetry, allowing for the selective formation of self-hybridized chiral exciton-polaritons. Our metasurface maintains maximal chirality for oblique incidence up to 20°, thereby outperforming all previously known designs. Moreover, we study the chiral strong-coupling regime in nonlinear experiments and reveal polaritonic signatures in chiral third-harmonic generation. Our results position maximally chiral van der Waals (vdW) metasurfaces as a versatile platform for tunable chiral polaritonics with applications in nonreciprocal photonic devices and valleytronics.