Rotating Angle Modulation Method for Improving the Measurement Performance of LRSPR Sensor

Long-range surface plasmon resonance (LRSPR) sensor has attracted extensive attention from research institutions and commercial companies due to its label-free detection, real-time analysis, high detection accuracy (DA) and high sensitivity. In this paper, a novel, simple, and effective rotating angle modulation (RAM) method for the metal-graphene structure LRSPR sensor is proposed. Compared with the general SPR sensor, the metal-graphene structure LRSPR sensor has a narrower full width at half maximum (FWHM) and a very high DA, especially the metal material is copper (Cu). The theoretical analysis for the Cu-graphene structure LRSPR sensor using RAM method shows that the FWHM, sensitivity and figure of merit (FOM) of the proposed sensor can be 0.74 degrees, 320.4 degrees/RIU and 498.24/RIU, respectively. In addition, this method enables the LRSPR sensor to obtain good measurement results even with the low-resolution rotating device and effectively reduces the dependence of the sensor on the high-resolution expensive rotating device. A preliminary comparative experiment for the SPR sensor has proved this new method. Finally, the concept of combining the RAM and general incident angle methods is proposed to provide the sensor with a large measuring range and low optical losses. We believe that this method can provide a favorable reference for solving the shortcomings of LRSPR sensors, such as complex structure, limited sensitivity and high cost, so that it can be widely promoted and applied in biological detection, medical assay, chemical investigation, etc.