Highly Sensitive Nanoscale Optical Sensor Based on Plasmonic Nanocavity Array

Micro-nanoscale optical sensors based on plasmonic nanocavities have attracted increasing attention in diverse applications. In this work, we propose a novel highly sensitive optical sensor based on plasmonic nanocavity array, which is promising in pressure and displacement sensing. The sensor is composed of a metal-insulator-metal (MIM) nanopillar array, which is covered by a gold film with a nanometer spacing, forming an array of nanocavities. A small displacement or pressure change can be detected by the large spectral shift due to the nanoscale change of the spacing between the MIM nanopillar and the metal film. Results show that one nanometer change of the spacing can lead to a shift of the reflectance dip of up to 42 nm with good linearity. We expect that this new nanocavity optical sensor will find potential applications in artificial intelligence, manufacturing industry, and medical diagnosis.