Theoretical Design of Plasmonic Refractive Index Sensor Based on the Fixed Band Detection

In this paper, we theoretically and numerically reported a simple plasmonic sensor design for the accurate detection of refractive index (RI). The sensing property was characterized by a derived theoretical model, which demonstrated the accurate sensing by measuring the intensity of a fixed narrow passband. It was found that the coupling phase modulation caused by the analyte was the main mechanism of the plasmonic sensing. The main advantage of this sensor design was that the sensing response band (or resonance wavelength) was fixed and narrow, even when the RI of analyte increases. Thus, an optical detector with certain working wavelength range can be used to detect the wide range of the RI, this was also confirmed by a two times narrower range than the common used approach in detecting the same analyte. The specific sensor design and the results may provide some guidance for the integrated plasmonic sensor design and make the sensor more flexible in the RI detecting.