Enhanced Second Harmonic Generation from a Waveguide-Integrated Plasmonic Fabry–Pérot Nanoresonator

A plasmonic nanoantenna can significantly improve the nonlinear effect owing to strong local electromagnetic fields and a large scattering cross-section. However, direct excitation using high-power incident laser light might destroy the nanoantenna, which hinders further improvement of the nonlinear effect. Here, we use a waveguide-integrated hybrid plasmonic Fabry–Pérot (FP) nanoresonator to achieve enhanced second-harmonic generation (SHG). The fabricated nanoresonator comprises a CdSe nanobelt sandwiched between a Au nanoparticle and a Au nanoplate. The CdSe nanobelt acts as a waveguide that guides light and also serves as a spacer with a high nonlinear susceptibility in the FP nanoresonator to enhance SHG signals. Resonance matching is achieved by tuning the CdSe size and the excitation wavelength. Consequently, a 10-fold increase in the magnitude of SHG is achieved compared to that in the scenario without a nanoparticle. A signal-to-noise ratio of 10.5 is achieved in the remote-excitation configuration, which is 1 order of magnitude higher than that in free-space SHG. This approach paves the way for the fabrication of nonlinear integrated devices and has potential applications in surface-enhanced Raman scattering, biochemical detection, and sensing.