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SYSM: Single Molecule Spectroscopy of Nanoobjects
SYSM 2: Single Molecule Spectroscopy of Nanoobjects II
SYSM 2.1: Invited Talk
Thursday, March 5, 2009, 14:00–14:40, VMP 8 HS
Single Emitters Coupled to Optical Nano-Antennas — Tim H. Taminiau1, Fernando D. Stefani1, Alberto Gonzalez-Curto1, and •Niek F. van Hulst1,2 — 1ICFO - the Institute of Photonic Sciences, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain — 2ICREA - Institució Catalana de Recerca i Estudis Avançats, Spain
We show how both excitation and emission of individual molecules is controlled by coupling to resonant optical nano-antennas. In these studies the single molecule approach is particularly effective as both position and orientation of the single absorber/emitter are well-defined. As a single absorber the molecule probes the local antenna field and here we show optical fields spatially localized within 25 nm at 514 nm wavelength for an 80 nm long Al resonant monopole antenna. Next the enhancement of the radiative and excitation rates is treated, particularly how the angular emission of the coupled system is highly directed. Clearly the dominant antenna mode determines the angular emission and arbitrary control over the main direction of emission is obtained, regardless of the orientation of the emitter. Finally a nano-Yagi-Uda antenna is discussed affording enhanced rates, strong unidirectional emission and, in reciprocity, efficient nano-focusing. The directivity is even more increased by the presence of a dielectric substrate, making such antennas a promising candidate for compact easy-to-address planar sensors at the single molecule level.