Near-infrared plasmonic-based fluorescence enhancement by silver-coated polymer pillar metasurfaces

A plasmonic metasurface was numerically designed and analyzed toward a realization of fluorescence enhancement in the near-infrared (NIR) region. The structure consists of silver (Ag) layer-coated subwavelength polymer pillar arrays on a glass substrate. Its parameters were derived using finite-difference time-domain simulation, and the device was prototyped using the 3D laser direct writing equipment combined with the DC sputtering technique to confirm the fabrication feasibility. As the structure works in the NIR range and has a low metallic fraction, it has low ohmic loss and shows high-fluorescent emitting enhancement (∼1063times) and directivity (∼1033times) near the edge of the top surface of silver-coated polymer pillars. The work provides an alternative approach to realize NIR fluorescence bioimaging and biosensing devices.