Departmental Seminar

Nanoscale (in)-coherent optical excitations in the electron microscope

Professor Albert Polman
Center for Nanophotonics, AMOLF, Amsterdam, the Netherlands

Cathodoluminescence imaging spectroscopy (CL) is a powerful tool to characterize optical nanomaterials at deep-subwavelength spatial resolution. In CL, a 5-30 keV electron beam is raster-scanned over the surface while the emitted radiation is detected. The electron beam creates a femtosecond electric field oscillation that couples strongly to polarizable electrons in the material, providing a spectrally broadband nanoscale probe of the local optical density of states. We use CL to image localized modes of resonant plasmonic and dielectric nanostructures and reconstruct their scattering wavefronts using CL holography. We show strong photon bunching using g(2) 2-photon correlation measurements on InGaAs quantum wells. Finally, we present the first data from our new femtosecond pulsed-laser driven time-resolved pump-probe CL microscope, unravelling the electron-induced NV0 « NV– state transfer of diamond NV centers and ultrafast carrier dynamics in semiconductors.

Albert Polman is program leader at the Center for Nanophotonics in the NWO Institute AMOLF in Amsterdam, the Netherlands, and Professor of Photonic Materials for Photovoltaics at the University of Amsterdam. Polman’s research group focuses on nanophotovoltaics, the study of light management at the nanoscale to realize solar cells with ultra-high efficiency that can be made at low costs, and develops cathodoluminescence spectroscopy as a super-resolution imaging technique for nanophotonics. Polman has published over 300 papers, has won several awards for his work, including two ERC Advanced Grants, and is member of the Royal Netherlands Academy of Sciences He is co-founder of Delmic BV that brings an instrument for cathodoluminescence spectroscopy on the market that was developed in his group.

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