Vertical plasmonic nanocavity array for sensing applications

摘要

Plasmonic nanostructures which exhibit resonant trapping and enhancing effects of light promise all the properties and capabilities required for sensing. To date, a large number of plasmonic structures have been demonstrated with various geometries, and most of them are 2D structures based on the lateral coupling of plasmonic nanoparticles, in which light is trapped and enhanced in nanogaps between separated nanoparticles (i.e., so-called “hot spots”). Despite the success, the 2D planar structures generally suffer a low absorption efficiency and high fabrication cost due to its stringent requirement for the nanometer gap size. To address the above issues, two types of vertically coupled plasmonic nanocavity arrays are developed in our group. They exhibit a near-unit light trapping efficiency with very large field enhancement and can be fabricated over a large area with low cost. Using these structures, we demonstrated very large fluorescence enhancement of infrared dyes over a large area, and a high precision (0.003 nm) distance sensing technique. Compared with the reported planar designs in previous works, the performances of vertical plasmonic nanocavities are significantly better, promising many important applications.