Nonlinearity enhancement via strong coupling in dielectric nanoantenna array-hyperbolic metamaterial systems

The development of materials with enhanced optical nonlinearities is critical for advancing integrated photonic systems. Herein, we propose a dielectric nanoantenna array-hyperbolic metamaterial (HMM) structure to boost optical nonlinearity, leveraging the strong coupling between the fundamental Mie resonance and the Ferrell-Berreman (FB) mode. We reveal that the Mie resonance strongly interacts with the FB mode, yielding a large Rabi splitting of up to 264 meV. The resonant frequencies of hybrid states and Rabi splitting are robust against variations in lattice period and incident angle. More importantly, strong coupling can significantly enhance the field confinement of hybrid modes within the ITO layers of HMM, resulting in a large nonlinear effective refractive index (n₂) of up to 4.4 × 10^-2cm²/GW, which is two orders of magnitude higher than that of the bare HMM, and maintains robust nonlinear enhancement across a broad spectral and wide incident angle range. Our findings open new avenues for high-performance nonlinear nanophotonic and optoelectronic devices in all-optical data processing and quantum information.