Simultaneous spatial and temporal control of the local excitation of a nanostructure using polarization-shaped laser pulses

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In this funding period, we want to establish coherent 2D nanoscopy in combination with pulse-shaping-based coherent control as novel methods for gaining insight into coherent ultrafast processes of nanoscale systems. Specifically we will study light-induced coherences in coupled (excitonic and/or plasmonic) systems and their transport with subdiffraction spatial and fs temporal resolution. For this purpose, we have demonstrated in the first funding period the adaptive and analytic control of nanooptical excitation as well as a new method for subdiffraction spectroscopy of electronic coherences. In the upcoming funding period, we plan to further develop, generalize, and ultimately to combine these methods, also with the help of additional technological advances. We will then apply these schemes to a number of nanoscale systems. Especially the technique of coherent 2D nanoscopy holds promise to observe processes of spatial–temporal correlations of electronic coherences and populations. With that method we carry the principle of nonlinear techniques from an ensemble measurement to the nanometer length scale and spatially localized few emitters. Thus we can map out nonlinear response functions in time/frequency as well as real space. 2D nanoscopy can be considered a generalization of time-resolved two-photon photoemission. We want to show that the 2D method can be of similar beneficial value for the field of photoemission research as it has proven to be for optical spectroscopy and NMR. It should thus become possible to study a broad range of fascinating quantum phenomena not accessible otherwise. Possible applications are envisaged in the nonlinear spectroscopy of nanostructures, molecules, or natural and artificial light-harvesting systems used in photovoltaics. Combination with the nanooptical excitation control will furthermore allow the direct spatially resolved study of transport processes.