Development of ultrafast nano-imaging with nanometer spatial and femtosecond temporal resolution

Many materials exhibit heterogeneous electronic and vibrational dynamics on nanometer spatial and picosecond temporal scales. To gain a better understanding of these elementary processes and their relation to observed macroscopic optical properties of interest, we require ultrafast nanoimaging with femtosecond temporal, nanometer spatial, and wavenumber spectral resolutions. Additionally, many transient effects in materials are long-lived and thus require low repetition-rate lasers (~1 MHz) for photoexcitation and probing, giving rise to difficulties in signal isolation. Previously established methods, such as ultrafast transmission electron microscopy (TEM), photoemission electron microscopy (PEEM), and X-ray microscopy, currently provide insufficient excited-state contrast. This talk will discuss an experimental implementation of heterodyne pump-probe infrared scattering-scanning near-field optical microscopy (HPP IR s-SNOM), which enables observation of light-matter interactions on these fundamental scales. In conclusion, we will provide a perspective on the application of HPP IR s-SNOM to a perovskite film to better understand how structural and compositional characteristics influence the emerging photovoltaic performance.