A grating-based plasmon index sensor: Performance simulation in the presence of noise

A sensing technique for refractive index based on the plasmon surface wave excitation on a metal grating is presented. The excitation is at its maximum and the reflection efficiency takes a minimum when the incident angle agrees with the resonance angle. Because the angle is a sensitive function of the index of the material put on the grating surface, we can find the index by measuring the resonance angle. Theoretical consideration including computer simulation finds that the index sensor can achieve 7-digit resolution based on efficiency-alone interrogation. In the present study we would like to examine the influence of noise possibly included in the experimental data. We first introduce a method of index determination proposed by Gong and others, where the authors employed a curve-fitting technique to get an accurate efficiency curve near the resonance angle and found detailed position of the resonance angle. Then, we apply their method to a sample data obtained by adding a set of Gaussian noise to a computational result and found the resonance angles in two cases: with and without the artificial noise. Provided the noise is sufficiently small, the curve-fitting works well in finding the resonance angle.