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Departmental Colloquium

Time-resolved optical microscopies of nanomaterials  
Guest Speaker
Prof. Dr. Achim Hartschuh  
Guest Affiliation
Department of Chemistry and Center for Nanoscience, LMU Munich, Munich, Germany  
Thursday, March 17, 2022 3:55 pm - 4:55 pm  
Zoom Meeting  

Time-resolved optical spectroscopic techniques provide direct insight into the excited state dynamics and energies of materials. Implemented in a microscopy platform, these techniques can be utilized to establish spatio-temporal maps and to visualize photo-induced phenomena. In this talk, I will discuss three different implementations developed to address particular sample properties. First, we use time-resolved photoluminescence (PL) microscopy to visualize charge carrier diffusion in hybrid halide thin films. We implemented a scheme in which the detection point is scanned with respect to the excitation point. Pulsed laser excitation in combination with time-resolved detection then allows for the observation of charrier transport within the film. In the second example, we implemented both transient absorption and time-resolved PL microscopy to study the ultrafast dynamics of excitons in single semiconducting carbon nanotubes. This allowed us to formulate a unified model by combining unimolecular exciton decay and ultrafast exciton-exciton annihilation on a time-scale reaching down to 200 fs. In the third implementation, we explore the non-linear response of plasmonic nanoantennas using phase-shaping of broadband laser pulses. We find that the enhancement provided by resonant nanoantennas can be predicted from a complex frequency dependent field enhancement factor. We then demonstrate that the spectral phase associated with this factor can be utilized for phase-selective confocal imaging.