Research team from Heidelberg and Milan develops novel microscopy technique to study energy materials

An extremely fast microscopy method to research the interaction of light and matter makes it possible to study optical processes on very short timescales. To this end, a German-Italian research team is combining holographic imaging with ultrafast spectroscopy in an innovative way. In this manner, even extremely short-lived electronic and magnetic phenomena – which play a major role in the development and application of novel energy materials – can be observed. The research was conducted as part of an international collaboration between scientists from the Institute for Physical Chemistry at Heidelberg University, the Polytechnic University of Milan, and the Institute for Photonics and Nanotechnologies in Milan (Italy).

At the heart of the research is a pump-probe microscope, which is used to conduct so-called excitation and detection experiments. In this process, the material under investigation is first excited by a short light pulse, while a second pulse records the time-dependent response. By comparing measurements taken with the excitation on and off, these processes can be accurately reconstructed. “Combining holographic imaging with ultrafast spectroscopy allows us to spatially resolve electronic and magnetic dynamics and track them on timescales ranging from femtoseconds to picoseconds,” explains Dr Julia Anthea Gessner, who does research as a project leader in the Collaborative Research Centre 1249 “N-Heteropolycycles as Functional Materials” and as a group leader at the Institute for Physical Chemistry.

The innovative method developed by the German-Italian research team makes it possible to simultaneously image ultrafast electro-magnetic phenomena across large fields of view, explains Dr Martin Hörmann of the Polytechnic University of Milan. Unlike other microscopy techniques, this enables the imaging of areas on the micrometer scale and generating time-resolved “films” of the charge and spin dynamics of electrons. In addition, light-induced changes in the optical properties of materials can be made visible in this way. “Our chiroptical approach thereby opens up entirely new possibilities for directly observing dynamic processes in complex materials,” says Dr Hörmann, who played a key role in the current research along with Dr Gessner and doctoral candidate Federico Visentin.

This high-resolution ultrafast imaging technique is intended primarily for use with energy materials. These materials are relevant to sustainable technologies such as solar cells, LEDs, spin-LEDs, or innovative electronic components. “The microscopy technique provides new insights into ultrafast optical processes, in particular with respect to how they change in response to the composition and structure of materials,” emphasizes Prof. Dr Felix Deschler, who does research at Heidelberg University’s Institute for Physical Chemistry. According to Prof. Dr Franco V. A. Camargo, a scientist at the Institute for Photonics and Nanotechnologies in Milan, research into the interaction of light and matter can provide important insights for the development of efficient and durable components for optoelectronics and spintronics.

The research was funded by the European Union. It was carried out as part of the Starting Grants awarded to Prof. Deschler and Prof. Camargo by the European Research Council (ERC). The results of the study were published in the journal “Nature Photonics”.