Hybrid Multibands of Surface Plasmon and Fabry-Pérot Resonances

We propose a novel approach for generating multiple bands in the energy-momentum dispersion relation of surface plasmon polaritons via coupling with cavity modes supported by long-period gratings. The multibands are induced by an anticrossing phenomenon that occurs between a surface plasmon resonance excited on a thin silver layer in the Kretschmann configuration and multiple Fabry-Pérot resonances in cavities defined by the gratings. The number and shape of the bands can be tuned via structural parameters, such as the period and height of the gratings. In particular, the bands become independent of the incident angle of light when the quality factor of the cavities is sufficiently high. Since the proposed structure is simple and the multibands have an angular tolerance for excitation, this approach has the potential for being utilized in practical nanophotonic applications, such as multiple fluorescence imaging and multiplex biosensors.