Near-Normal Incidence Dark-Field Microscopy: Applications to Nanoplasmonic Spectroscopy


Jonathan A. Fan, Kui Bao, J. Britt Lassiter, Jiming Bao, Naomi J. Halas, Peter Nordlander, and Federico Capasso. 2012. “Near-Normal Incidence Dark-Field Microscopy: Applications to Nanoplasmonic Spectroscopy.” NANO LETTERS, 12, 6, Pp. 2817-2821.
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The spectroscopic characterization of individual nanostructures is of fundamental importance to understanding a broad range of physical and chemical processes. One general and powerful technique that addresses this aim is dark-field microscopy, with which the scattered light from an individual structure can be analyzed with minimal background noise. We present the spectroscopic analysis of individual plasmonic nanostructures using dark-field illumination with incidence nearly normal to the substrate. We show that, compared to large incidence angle approaches, the near-normal incidence approach provides significantly higher signal-to-background ratios and reduced retardation field effects. To demonstrate the utility of this technique, we characterize an individual chemically synthesized gold nanoshell and a lithographically defined heptamer exhibiting a pronounced Fano-like resonance. We show that the line shape of the latter strongly depends on the incidence angle. Near-normal incidence dark-field microscopy can be used to characterize a broad range of molecules and nanostructures and can be adapted to most microscopy setups.
Last updated on 06/02/2020