Measuring the spatio-temporal field of ultrashort pulses near nanostructures.

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The interaction of ultrashort pulses of light with matter on the nanoscale is of fundamental importance in optoelectronics and nanophotonics. Ultrashort pulses excite nanostructured materials over a wide range of different frequencies so that the resulting superposition of these field distributions, with different frequencies determines the actual local field evolution. Hence, controlling the spectral phase of the illuminating laser pulses offers direct control over the space and time-evolution of the local optical fields on femtosecond timescales. However, spatio-temporal dynamics of optical fields localized on the nanoscale has so far been hidden from direct access in both in real space and in the time domain. In this project we aim to combine two powerful techniques, near-field scanning optical microscopy and spectral interferometry, to measure full time-dependent optical fields in and around nanostructures for ultraweak femtosecond pulses with nanometer spatial and femtosecond temporal resolution. Because the technique is linear it can be used for extremely weak pulses that on average contain less than a fraction of a photon per pulse. This extreme sensitivity opens up many fascinating research avenues in coherent control, nano-optics, quantum information and other research fields that investigate the interaction between light and matter with high spatial and temporal resolution.