Grating-assisted hybrid plasmonic slot resonator for on-chip SERS sensor with built-in filter

A grating-assisted hybrid plasmonic slot resonator is proposed and theoretically investigated as an on-chip surface-enhanced Raman scattering (SERS) sensor. A dielectric Bragg grating and a gold baffle are introduced into the hybrid plasmonic slot waveguide as two mirrors to form a plasmonic–dielectric cavity, in which the constructive interference of the input pump light greatly enhances the electric field. The grating reflects the wasted pump light for reverse secondary coupling and acts as a built-in notch filter for filtering out pump light from Raman scattered light simultaneously, improving the coupling efficiency and realizing a compact and miniaturized on-chip SERS sensor. Both the volumetric electric field enhancement and Raman collection efficiency are taken into account. The proposed scheme provides a simple, effective and universal method for improving the performance of the plasmonic-antennas-type waveguide-based SERS sensors.