Sensing performance enhancement of plasmonic waveguide sensor using a bimodal strategy with digital Gaussian filter

Abstract

In this paper, a novel bimodal strategy with digital Gaussian filter was proposed to improve the sensing performance of plasmonic waveguide sensor (PWG). The central angle of the bimodal spectrum is adopted rather than the traditional resonance angle. Compared with conventional noise reduction algorithm, the proposed digital Gaussian filter would transform resonance dip into bimodal spectrum and then improve both sensitivity and signal-to-noise ratio. Expected angle and FWHM (full width at half maximum) of Gaussian filter are two significant parameters to optimize sensing performance for each specific waveguide spectrum. The sensitivity and standard deviation of TM1 mode were measured as 90.715 deg/RIU and 7.515 × 10−5 deg, respectively, which are better than those of TM1 PWG sensor. Its RI resolution was then calculated to be 8.28 × 10−7 RIU, which is double-fold lower than that of TM1 PWG sensor, that is 1.73 × 10−6 RIU. For biosensing application, the limit of detection (LOD) of 29.15 mg/L, that is 0.16 mM, was obtained for glucose molecule, according to the three-fold standard deviation theory. For BSA detection, the LOD as high as 0.949 pM was achieved, which is approximately 2.8-fold lower than that of PWG sensor. It is also nearly two orders of magnitude lower than that of gold based SPR sensor, which is 91.33 pM.