Multi-plasmon resonances enhanced two-photon coherent anti-Stokes Raman scattering by nanorods

The development of new structures allows two-photon coherent anti-Stokes Raman scattering (TPCARS) to be strongly enhanced by multiple surface plasmon resonances (MSPRs). In this paper, plasmonic structure consisting of two Ag nanorods is designed and the enhancement of TPCARS is investigated. By properly selecting designing structure parameters, strong MSPRs peaks at 1020 nm and 505 nm are obtained, which can enhance the TPCARS signal based on the frequency match of the fundamental frequency and frequency doubling. The enhancement factor of TPCARS can reach as high as 3.66 × 10²⁸ with significant electric field enhancements under appropriate selection of system parameters. Furthermore, the two-photon process can be controlled at different optical frequencies by changing the geometric parameters of Ag nanorods. The new scheme advanced in this work can help to achieve single molecule level of CARS, and may have a potential to increase the intensity and resolution of nonlinear optical imaging.