Numerical investigations of a near-infrared plasmonic refractive index sensor with extremely high figure of merit and low loss based on the hybrid plasmonic waveguide-nanocavity system.

With vertically slotted hybrid plasmonic waveguides (VSHPWs)-nanocavity system fabricated on the silicon-on-insulator platform, a near-infrared surface plasmon resonances (SPRs)-based refractive index (RI) sensor with extremely high figure of merit FOM = 224.3 and transmission efficiency T = 97.6% is proposed and investigated. Based on the finite element method, effective mode index behaviors together with spectral properties are calculated to analyze and optimize the sensing performance. Within near-infrared region, the wavelength sensitivity (S) and optical resolution (FWHM) can be achieved as S = 1817.5nm/RIU and FWHM = 7.4nm. A mechanism of synergy between propagating SPRs and localized SPRs is also presented for further improving the sensitivity (as high as 2647.5nm/RIU). In addition, the VSHPWs-based RI sensor can be fully realized by CMOS-compatible fabrication technology. In general, the high FOM, S and T achieved by our designed structure may have extensive applications in nanophotonic circuits, environmental monitoring and even pharmaceutical research.