Coupling of Fabry–Pérot Cavity and Metallic Nanograting Array for High-Quality-Factor Plasmonic Modes

Abstract

The quality (Q) factors of surface plasmons (SPs) is crucial for enhancing optical field localization and optimizing the performance of optical devices, offering broad potential applications in nanolasers, photonic sensing, and nonlinear optics. To further improve the Q factors of SP modes and achieve efficient modal control, this study proposes a composite structure that integrates a Fabry–Pérot (FP) cavity with a metallic nanograting array. By leveraging the strong coupling between the resonant modes of the FP cavity and the plasmonic resonances of the grating array, the structure induces Fano resonance, thereby realizing plasmonic modes with narrow linewidths and high Q factors. The results demonstrate that this composite system can achieve a Q factor as high as 182.5 when the FP cavity thickness is 700 nm and maintains a stable high Q factors within the cavity thickness range of 670-750 nm. Moreover, the introduction of the FP cavity not only optimizes the radiation loss of the plasmonic modes but also provides a flexible means of spectral tuning. By adjusting the geometric parameters of the FP cavity, the resonance behavior of the plasmon-cavity modes can be effectively controlled, offering a novel strategy for designing high-performance nanophotonic devices. This high-Q plasmonic platform holds significant application value in nanophotonics, on-chip photonics, and high-sensitivity sensing.