Tracking femtosecond dynamics at the nanoscale

NanoPhotonics and NanoOptics (NANOP) addresses the interaction of light with nanostructures that are too small and complex tobe described by traditional continuum methods, and the structuring andmanipulation of optical fields... [ view full abstract ]

NanoPhotonics and NanoOptics (NANOP) addresses the interaction of light with nanostructures that are too small and complex tobe described by traditional continuum methods, and the structuring andmanipulation of optical fields to control these interactions at the nano-scale.Applications are found in 2D-materials, perovskites, photo-voltaics, polymers, molecular biophysics, cold atoms, quantum optics etc... Natural Photosynthetic systems in plants and bacteria constitute a particular Nano-Micro system ranging from individual chlorophyls to full complex networks, moreover acting on the ultrafast fs-ps scale. Photosynthetic light harvesting works highly efficient and even signatures of coherent energy transfer have been revealed.Yet the complexes in natural membranes are too small and fast to track the nanoscale light transfer. We aim to combine ultrasmall and ultrafast, to couple efficiently to single units, to track fs transient spectra and to control theinteraction.

I will introduce a novel experimental technique that allows for the direct recording of ultrafast transient absorption spectra of single molecules in a broadband fashion, at room temperature, with a temporal resolution of 25 fs, to reveal a dynamic Stokes-shift alongside vibrational cooling within the first tens of femtoseconds after photoexcitation. Beyond single moleculedetection by fluorescence, I’ll enter into the alternative detection of stimulated emission.

Finally, imaging nanoscale light transport requires local excitation and detection far beyond the diffraction limit. I will address the use of scanning resonant antenna probes and nanoholes to confine the light field and couple effectively to single emitters on the nanoscale. The plasmonic antenna acts as a nano cavity with relative strong coupling (~100GHz), speeding up the radiative decay to picosecond time scale, enhancing the photo-stability and allowing > GHz single photon emission.

I will conclude with an outlook of the challenges ahead and the perspectives of addressing coupled networks in real nano-space and on femtosecond timescale.