ANNE-LISE VIOTTI

Scientists have for years successfully manipulated materials to produce structures with extremely small sizes, at the nanometer scale (10^-9 meters). Miniaturization of transistors, the fundamental building blocks of our computers and smartphones, allows making very powerful computing chips that fit on one fingernail. Some nanostructures also interact with light in surprising ways. For instance, thin semiconductor needles, also called “nanowires”, efficiently absorb sunlight and convert it into electrical power. Future solar cells utilizing these advanced devices are expected to surpass the efficiency of currently commercialized solar panels. Other types of structures are designed to concentrate the light into the tiniest spots. Such device finds application in healthcare by acting as a non-invasive sensor and will be able to detect single molecules.

Naturally, scientists are faced with a number of challenges when studying nanostructures. First, they cannot take images with a conventional light microscope as optical diffraction fundamentally limits the spatial resolution. Instead, they have to use electrons ripped off the surface of the nanostructures to form pictures. Second, many of the processes they want to investigate happen on very fast time scales, within few femtoseconds, i.e. 10^-15 seconds! The only way to take snapshots of these events is to use laser pulses with femtosecond duration, which act as a flash of a camera. Lastly, some of the ultrafast processes in specific materials can only be triggered if the light carries a sufficiently high energy, or in other words very short wavelength down to the extreme ultraviolet.

In standard laboratory settings, there can be a number of obstacles to such experiments, for instance: the complex and inefficient generation of ultrashort laser pulses or the limited tunability of the light frequency for element selectivity. In contrast to large facilities such as Free Electron Lasers, this project will provide a compact optical platform for time- and spatially-resolved experiments. Anne-Lise Viotti  will combine the research fields of ultrafast lasers, nonlinear optics, atomic physics and material science to realize a compact and efficient light source to perform electron microscopy experiments at the nanometer and femtosecond scales. High-power, industrial laser systems will be employed and the light will be manipulated temporally and spectrally to operate on the fastest time scales and allow chemical sensitivity in the materials investigated.