We have developed a far-field optical approach capable of mapping the local density of states (LDOS) of plasmonic structures with a spatial resolution in the order of ~10nm, well below the diffraction limit of light. Our method is based on the simultaneous localization of single fluorescent emitters with an EM-CCD camera, and the detection of their fluorescence lifetime with a time-resolved avalanche photodiode. This approach is compatible with unknown and non-periodic samples, as it makes use of a dense labeling strategy with photoactivatable fluorophores who are stochastically activated over time.
We demonstrate the performance of our technique by studying the lifetime reduction induced by a silver nanowire, obtaining a super-resolved mapping of the LDOS with a localization precision of 6 nm and a temporal resolution down to 100 ps. We believe that our technique, which can be implemented in any wide-field inverted microscope, does not require scanning parts, and performs far-field measurements at the molecular level, opens up a wide range of applications spanning from nanophotonics to biological imaging.
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