Coexisting strong and critical coupling in a silicon quasi-BIC metasurface integrated with monolayer WS 2
Year: 2026
Type: article
Abstract: excitons and quasi-bound states in the continuum (q-BIC) resonances in a slotted Si disk metasurface is demonstrated. By controlling the slot width, the radiative damping rate is tuned. Systematic adjustment of disk radius and height enables continuous spectral tuning of the q-BIC mode from 520 to 650 nm, while maintaining a fixed q-BIC damping rate. Clear anti-crossing behavior is observed in the absorbance spectra, confirming hybrid exciton-polariton formation over a wide range of cavity damping rates. A room-temperature Rabi splitting of 47.7 meV is observed under specific height-tuned conditions and with a q-BIC linewidth of 15.1 meV. While the Si q-BIC cavity has contributions to both the radiative and nonradiative losses, careful tuning of the damping rate allows for matching of the total radiative and non-radiative losses in the hybridized system, achieving the critical coupling condition when these dissipative and radiative channels become comparable. It is demonstrated that large absorbance enhancement in the polariton branches can be achieved, with a value close to the theoretical maximum of 0.5 in the upper and lower polariton branches. These findings demonstrate that strong coupling and critical coupling can coexist in a lossy dielectric metasurface, extending exciton-polariton physics beyond near-lossless photonic systems. The results may also guide further exploration of Si metasurfaces for polariton light-emitting or lasing devices on the CMOS-compatible platform, with the additional advantage of compatibility with active functionality.
Source: Optics Express
DOI: 10.1364/oe.613126
Authors: Yongliang Zhang, Xia Zhang, A. Louise Bradley
Institutions: Trinity College Dublin, Tyndall National Institute
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,270
OpenAlex ID: W7221053960