Near-field optical imaging of transient absorption dynamics in organic nanocrystals

Collection-mode near-field scanning optical microscopy is combined with femtosecond two-color pump-probe spectroscopy to study the transient absorption dynamics in organic crystals. The temporal evolution of the variation in the nonlinear transmittance of nanostructures is mapped with a spatial resolution of 200 nm and temporal resolution of 150 fs. Near-field time-resolved measurements indicate a nonradiative energy transfer from the excited molecules to the metal coating of a near-field probe.