Abstract
A refractive index sensor using two concentric triple racetrack resonators with plasmonic metal–insulator–metal (MIM) waveguides is suggested to provide more freedom for sensing applications. Due to momentum matching, intensive coupling happens between the equivalent modes of each section of the resonators. The sensing properties are numerically discussed in terms of the finite difference time domain method. According to the outcomes, when increasing the refractive index of the material in the outer sections of the racetrack resonators, the dip wavelengths show a notable red shift. The sensing performance can be enhanced by using two multiple concentric resonators that effectively increase the strength of the light–analyte interaction, which is useful for sensing applications. Our proposed nanosensor offers a high sensitivity value, sensing resolution, and figure of merit of 1618 nm/RIU, ${6.18} \times {10}^{ - 4}\,\,{\rm{RIU}}$, and $89\,\,{\rm{RI{U}}^{ - 1}}$, respectively. Also, the racetrack resonators coupled to MIM waveguides can be simply integrated into chip circuits with other optical devices to perform monitoring and filtering tasks.
© 2019 Optical Society of America
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