Plasmonic micropipe spectral filters in mid-infrared

Multispectral analyzers based on nanostructured plasmonic spectral filters can potentially find a wide range of applications. However, spectral filters based on the widely reported microhole or ring arrays suffer from relatively wide filtering bands, resulting in a relatively low spectral resolution. In this work, we fabricate high-performance spectral filters based on vertically standing micropipes on a silver film. An infrared spectral microscope is used to investigate the properties of these micropipe spectral filters. The results indicate that the micropipe spectral filters have a full width at half-maximum ∼5 times smaller than the microhole filters at the same wavelength. Micropipe spectral filters are expected to significantly improve the spectral resolution of multispectral analyzers.