Implementation and testing of a compact and high-resolution sensing device based on grating-coupled surface plasmon resonance with polarization modulation

An experimental setup exploiting grating-coupled surface plasmon resonance (GCSPR) technique based on polarization modulation in conical mounting is presented for the first time. A metallic grating is azimuthally rotated in order to support excitation of surface plasmon polaritons (SPPs) with enhanced sensitivity. In correspondence of SPP resonance, a polarization scan of the incident light is performed and reflectivity is collected. Output signal exhibits harmonic dependence on polarization and the phase term is exploited as a parameter for sensing analysis. Since the sensing configuration is kept fixed during the analysis and the only degree of freedom is represented by the incident polarization, the mechanical complexity of this SPR system is significantly reduced with respect to other configurations. Moreover the setup assures competitive performance in refractive index sensitivity and resolution. The assembled prototype is tested for fluid analysis with an embedded glass/PDMS microfluidic cell fabricated by soft-lithography procedure. A model biorecognition assay based on avidin/biotin reaction was considered in order to test the detection performance of the presented setup.