High-sensitivity plasmonic sensor based on perfect absorber with metallic nanoring structures

We propose a nanoring array structure backed by a metal mirror to achieve perfect infrared absorber with absorption as high as 99.99%. The frequency of the absorption peak strongly depends on the refractive index surrounding the structured surface, while the maximum of absorption remains constant with varying the surrounding refractive index. These features can be used as plasmonic sensor for refractive index measurement. This plasmonic sensor possesses the figure of merit 700. In addition, we investigate the effect of various materials on the performance of the sensor, including SiO2, TiO2, TiN, and Al2O3 dielectric spacer and Au, Ag, Al, and Cu back plate and top structure. Due to the high sensitivity and simple sensing scheme, the sensing strategy can find potential applications in chemical and biosensor applications.