Abstract
A high-performance grating coupled surface plasmon resonance (GCSPR) sensor based on Al-Au bimetallic layer is proposed. High sensitivity is obtained by replacing the positive diffraction order with negative diffraction order of metallic grating to excite the surface plasmon. Compared with the conventional Au-based GCSPR sensor, the sensor with aluminum as the SPR active metal exhibits a sharper (i.e. larger depth-to-width ratio) reflectivity dip, which increases the signal-to-noise ratio (SNR) and enhances its resolution. In addition, an ultrathin gold film is deposited on the grating surface in order to protect the Al layer from getting oxidized. Numerical simulations show that the angular sensitivity of the sensor reaches 187.2°/RIU (degree per refractive index unit) with good linearity and the FWHM (full width at half maximum) of the resonant dip is only 0.93°.
Highlights
Surface plasmon resonance (SPR) has been widely used in a variety of sensing applications, since it provides high sensitivity, label-free, real-time and rapid sensing capability for detecting biomedical and biochemical reactions on a surface. (Nylander et al, 1982, p.79; Matsubara et al, 1988, p.1160; Homola, 1999, p.3)
All the grating-based methods above are improving the sensitivity through making the dips of the 1st diffraction order better, which can not exceed the sensitivity of the prism-based systems
We present a grating coupled surface plasmon resonance sensor with aluminum as the active metal
Summary
Surface plasmon resonance (SPR) has been widely used in a variety of sensing applications, since it provides high sensitivity, label-free, real-time and rapid sensing capability for detecting biomedical and biochemical reactions on a surface. (Nylander et al, 1982, p.79; Matsubara et al, 1988, p.1160; Homola, 1999, p.3). Byun’s group proposed a grating-coupled transmission-type SPR sensor with a refractive index sensitivity of 70°/RIU by resonant coupling surface plasmon to radiation modes. From the report of Cai (2008,p.14597), the refractive index sensitivity of grating-based SPR sensors is improved into more than 237°/RIU by double-dips method. According to his report, the price paying for this sensitivity enhancement is the additional uncertainty of estimating two spectral shifts instead of one in the conventional methods based on single resonant dip. We present a grating coupled surface plasmon resonance sensor with aluminum as the active metal. High refractive index sensitivity is obtained by exciting the surface plasmon with -1st diffraction order of metallic grating. The physical explanation related to the results has been provided
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