Dielectric waveguide-enhanced localized surface plasmon resonance refractive index sensing

We theoretically show a high-performance refractive index (RI) sensor that consists of a two-dimensional (2D) gold nanoparticle array lying on a dielectric slab waveguide. The sensor has high RI sensitivity and figure of merit (FOM), reaching 250 nm/RIU and 28, respectively. Such a high RI sensitivity and FOM result from a sharp fanolike resonance, which is caused by the interference between the localized surface plasmon resonances (LSPRs) excited on individual gold nanoparticles and the waveguide mode propagating in the adjacent dielectric slab. The interference condition is that the electric field of the waveguide mode must be parallel to the polarization direction of the LSPRs. Our work may have potential applications in ultra-compact biomedical sensing.