Ultra-high sensitive plasmonic refractive index sensor based on ring resonator

In this paper, an ultra compact surface Plasmon (SP) sensor based on ‘ring resonator coupled metal-insulator-metal (MIM) waveguide’ is theoretically studied and numerically simulated by finite difference time domain (FDTD) method. Ring and waveguide is filled by material to be sensed and implanted in a silver medium whose frequency dependent relative permittivity is characterized by Drude model. Any change in refractive index of material to be sensed leads to variation in resonance condition. Refractive index of the medium can be sensed by detecting resonant wavelength of the ring resonator. Due to the confinement of material to be sensed and optical energy to same area, light- matter interaction increases, and hence, an ultra high value of sensitivity(S=1235 nm per refractive index unit) is obtained. Sensitivity can be further increased with increasing radius of resonator but at the cost of increased propagation losses and size of the device. Device offers an ultra large value of sensitivity that opens its opportunity to be used in biological and biochemical sensors.