Plasmonic tip internally excited via an azimuthal vector beam for surface enhanc

The synergy of a plasmonic tip and fiber-based structure light field excitation can provide a powerful tool for Raman examination. Here, we present a method of Raman spectrum enhancement with an Ag-nanoparticles (Ag-NPs)-coated fiber probe internally excited via an azimuthal vector beam (AVB), which is directly generated in a few-mode fiber by using an acoustically induced fiber grating. Theoretical analysis shows that gap mode can be effectively generated on the surface of the Ag-NPs-coated fib