Design and Polarization Control of the Modal Splitting in Hybrid Anisotropic Nanocavities

The strong coupling of optical resonators results in a mode splitting proportional to the coupling strength, which can be achieved with metal-dielectric-metal (MDM) cavities that have similar thickness and refractive index. However, an active control of the mode coupling is challenging. Here, an alternative configuration of an MDM cavity coupled with a Guided-Mode-Resonator (GMR) is explored. The GMR grating is fabricated on top of the MDM cavity, such that the coupling can be tuned by the thickness of the central metal. The typical modal anti-crossing (with a splitting of approximate to 50-65 meV) detected in the angular dispersion of the GMR-MDM is observed. Excellent agreement of the experimental reflectance with simulations allows to report the angular dispersion from -50 degrees to 50 degrees. The anisotropy of the GMR modes enables to switch in and out of the strong coupling by changing the polarization of the incident light. Moreover, the asymmetry of the GMR-MDM architecture induces a side-dependent response. The MDM cavity is only transparent at its resonances, which leads to a suppression of all modes outside the resonance bands when impinging from the MDM side. These features are highly interesting for optoelectronic applications such as optical switches and multi-level optical multiplexing.