Highly Sensitive Surface Plasmon Sensor With an Ultra-Narrow Linewidth

Plasmonic sensors based on noble metals are widely applied in medical diagnostics, biochemical assays, and environmental monitoring. Due to poor adhesion between Au or Ag and dielectric materials, it is necessary to add reactive metals between inert noble metal and dielectric substrate to increase adhesion during the fabrication of plasmonic sensors. However, commonly used reactive metals such as Ti and Cr have weak plasmonic effects, which limit the sensing performance of plasmonic sensors. Herein, we propose a nanosystem consisting of Au grating, Cu film, and SiO2 substrate. The introduction of Cu material not only supports the high sensitivity of the nanosystem, but also eliminates the need to add adhesive metals between the Au grating and SiO2 substrate in practical preparation. The nanosystem exhibits a reflection dip with an ultra-narrow linewidth of 1.8 nm, which is caused by the surface plasmon polaritons (SPPs) mode at the interfaces of Au/air and Cu/air. The nanosystem shows a good sensing performance with a sensitivity of 1200 nm/RIU and a maximum figure of merit (FOM) of 631.6 /RIU. The proposed nonosystem provides practical significance for the application of highly sensitive plasmonic sensors.