Plasmonic platforms for innovative surface plasmon resonance configuration with sensing applications

摘要

An experimental prototype exploiting Grating-Coupled Surface Plasmon Resonance (GCSPR) based on polarization modulation has been assembled and tested for sensing purposes. The plasmonic gratings are azimuthally rotated in order to exploit the symmetry breaking for the excitation of highly sensitive Surface Plasmon Polaritons in conical mounting. By exploiting the optimal-polarization shift, a scan of the incident polarization is performed and reflectivity data are collected. The output signal exhibits a harmonic dependence on polarization and the phase term is considered as a parameter for sensing. Since the optical configuration is fixed during the analysis and the only degree of freedom is represented by the incident polarization, this setup provides a more compact and simplified architecture with respect to other commercial SPR techniques, however assuring at the same time competitive performances in refractive index sensitivity and resolution. The employed metallic gratings are fabricated by interferential lithography and replicated onto resin substrates by soft-lithography techniques, thus thermally evaporated.