Excitation of Bloch surface wave using silver nanoparticles for sensitivity enhanced biosensor

A silver nanoparticles array is introduced on the top layer of all-porous-silicon refractive index sensor. Bloch surface wave (BSW) resonance is realized at the interface between air and multilayer porous silicon structure, which can be excited by different coupling schemes: the Kretschmann prism and silver nanoparticles array. In addition to sustaining the BSW mode, the silver nanoparticles add an additional degree of freedom to the phase-matching conditions. We demonstrated the sharp BSW reflectivity dip with an ultra-narrow linewidth. The performance of the designed BSW sensor is numerically calculated by the rigorous coupled wave analysis (RCWA) method under s-polarized light. The optimized silver nanoparticles coupled BSW (AgNPs-BSW) sensor has a much higher figure of merit (similar to 17000R/U-1) than conventional prism-coupled BSW sensors. The azimuthal sensitivity can reach about 703 degrees/RIU or even higher. The proposed silver nanoparticles coupled BSW (AgNPs-BSW) sensor exhibits the capacity to eliminate the adverse effects of inhomogeneous penetration of analytes. With such excellent performance, our study demonstrates its potential applications in the field of chemical and biological sensors in the future.