Invited Paper
Probing the Local Density of States of Plasmonic Nanostructures with a Single Quantum Emitter

Single quantum systems are ideal probes for the local electromagnetic environment. Their single system nature gives rise to a high resolution ­- in space as well as in the time domain, since any ensemble averaging is avoided. Its photostability and ability to emit photons even at room temperature makes the nitrogen vacancy center (NV center) in nanodiamond an excellent probe for this purpose. Its position can be manipulated with an atomic force microscope (AFM) in a controlled manner to obtain maps of its decay rate [1].

Here, we employ a single NV center glued to the tip of an AFM as a scanning fluorescence lifetime probe. We demonstrate three-dimensional quantum emitter fluorescence lifetime imaging microscopy (QE-FLIM) by scanning various plasmonic structures, such as silver nanowires or gold nanospheres [2]. The possibility to pre-characterize the probe at known structures and compare the results to theory enables for quantitative measurement of the local density of optical states (LDOS) on the nanoscale. Our scanning scheme collects data in all three spatial dimensions, which makes a correction for topography artifacts possible and even allows for the identification of buried structures. Future applications of our technique may range from special topics like engineering of single photon sources or improving light trapping in solar cells to broader fields like materials science and biotechnology.

References

[1] A. W. Schell, G. Kewes, T. Hanke, A. Leitenstorfer, R. Bratschitsch, O. Benson, and T. Aichele, Opt. Express 19, 7914-7920 (2011)

[2] A. W. Schell, P. Engel, Philip Engel, Julia F. M. Werra, Christian Wolff, Kurt Busch, and O. Benson, Nano Lett. 14, 2623−2627 (2014)

oliver.benson@physik.hu-berlin.de