Metallic nano-antennas provide strong field confinement and intensity enhancement in hotspots and thus can ultimately enhance fluorescence detection and provide ultra small detection volumes. In solution-based fluorescence measurements, the diffraction limited focus driving the nano-antenna can outshine the fluorescence originating from the hotspot and thus render the benefits of the hotspot negligible. We introduce a model to calculate the effect of a nano-antenna, or any other object creating a nontrivial intensity distribution, for fluorescence fluctuation measurements. Approximating the local field enhancement of the nano-antenna by a 3D Gaussian profile, we show which hotspot sizes and intensities are the most beneficial for an FCS measurement and compare it to realistic antenna parameters from literature.

OSA
doi.org/10.1364/OE.22.015397
Opt. Express
Resonant Nanophotonics

Langguth, L, & Koenderink, A.F. (2014). Simple model for plasmon enhanced fluorescence correlation spectroscopy. Opt. Express, 22(13), 15397–15409. doi:10.1364/OE.22.015397