Plasmonic hybridized modes empowered by strong plasmon interaction in the nanograting-dielectric-metal stacked structure

The coupling between surface plasmon polaritons (SPPs) and waveguide (WG) modes has been widely investigated by using prism-coupled structures and has demonstrated a large number of interesting physical phenomena. However, these conventional structures mainly rely on the angle-dependent total internal reflection excitation. This is not conducive to their further development due to the large volume and the requirement of oblique incidence. In this paper, we theoretically propose a three-layer nanograting-dielectric-metal (NDM) plasmonic structure. Within this structure, a thickness-dependent plasmonic WG (PWG) mode in the middle dielectric cavity strongly couples with SPPs on the top surface, resulting in two new hybridized PWG-SPPs modes. This hybridization coupling phenomenon is analyzed in detail by using plasmonic hybridization and two coupled oscillator models. Besides, a thorough investigation is conducted on the sensing performance of these two PWG-SPPs hybridized modes. The difference in sensing characteristics between these two hybridized modes can be well explained by their coupling strength variation. This NDM plasmonic nanostructure owns unparalleled advantages in the generation and modulation of a variety of new modes, effectively promoting the development of miniaturized optoelectronic devices.