Pump-probe scanning near field optical microscopy: Sub-wavelength resolution chemical imaging and ultrafast local dynamics

Results of two color femtosecond time-resolved pump-probe experiments using scanning near field optical microscopy on thin films of organic semiconductor 3,4,9,10 perylenetetracarboxylic dianhydride are presented. With this technique, quantitative information on exciton dynamics with high temporal and spatial resolution can be obtained by fitting a rate model to the transient absorption spectra. Additionally, the chemical selectivity inherent to this technique enhances the contrast, which could be used for video-rate imaging when high-repetition rate lasers are used. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3701724]