High Sensitivity Transmission-Type SPR Sensor by Using Metallic--Dielectric Mixed Gratings

We theoretically investigate transmission-type SPR sensors with novel metallic--dielectric mixed gratings by rigorous coupled-wave analysis (RCWA), compared to the conventional dielectric gratings based structure. It is found that the transmittance efficiency and the full width at half-maximum (FWHM) of the transmission curve can be modulated by increasing or decreasing the metallic part. Therefore, appropriate proportion of metal part will induce enhancement factor of sensor merit. Furthermore, this novel structure will also bring enhancement of resonant angle shift, which can be explained by plasmonic interpretation based on a surface limited increase of interaction
area and excitation of localized surface plasmons (LSPs). The proposed configuration has a wide range of potential applications not only as sensor but also other optical devices.