WS₂–Flake-Sandwiched, Au-Nanodisk-Enabled High-Quality Fabry–Pérot Nanoresonators for Photoluminescence Modulation

The increasing demand for compact and high-performance photonic devices drives the development of optical resonators with nanoscale sizes and ultrahigh quality factors. Fabry–Pérot (FP) resonators, the most widely employed optical resonators, can support ultrahigh quality factors in the simple structure, which is particularly attractive for applications in lasers, filters, and ultrasensitive sensors. However, the construction of FP resonators with both nanoscale sizes and high quality factors has still faced challenges. Herein we demonstrate the construction of FP nanoresonators out of single Au nanodisks (NDs) and a Au film, with a WS₂ flake sandwiched in between. The atomically flat surfaces of the WS₂ flake and Au NDs benefit mirror alignment and boost the quality factor up to 76. The nanoresonators can support FP resonances with different mode orders in the visible region. The optical properties and formation mechanisms of the high-quality FP modes are systematically studied. The FP modes are further hybridized with excitons in the WS₂ flake spacer, enabling the modulation of the WS₂ indirect band gap emissions. Our study combines the advantages of plasmonic nanoparticles and FP resonators, providing a promising platform for the development of compact nanophotonic devices such as tunable nanolasers, smart sensors, and photonic-circuit elements.