When femtosecond lasers – ultrashort pulse lasers used in high tech applications – irradiate a metal surface, they leave behind damages on the nanoscale that look like miniature moon craters. For his PhD project, Dr Igor Milov combined various theoretical models into a single computational tool that models the damage caused by ultra-short laser pulses of various wavelengths. For this reason, Igor has been awarded a cum laude degree.
Studying the underlying fundamental processes that occur when metal thin films are exposed to high doses of Extreme Ultraviolet (XUV) or X-ray laser radiation is challenging due to its multi-scale and multi-physical nature. The corresponding knowledge was insufficient to be used for in-depth understanding and predicting material damage under real operational conditions at free electron lasers. “There are a lot of studies on the damage done by lasers in the visible light spectrum”, says Igor, “my research bridges the gap between the knowledge of optical lasers and XUV/X-ray lasers.”
Understanding of the damage processes induced by XUV/X-ray lasers provides a possibility to design damage-tolerant optical elements for synchrotrons and free electron lasers. In a broader view Igor’s research can contribute to other laser damage topics that primarily utilize optical lasers. Apart from avoiding damage as in the previous example, his understanding of light-matter interaction can be used to produce damage, but in a smart and useful way. Our model can help to find the settings for a laser to damage the surface of a metal in such a way that its optical, mechanical, and chemical properties change.
For example, to make the surface of a certain metal hydrophobic or to increase its catalytic and plasmonic activity. The laser can also produce nanoparticles that have medical applications. These nanoparticles are normally produced chemically but this results in residue from the chemicals which makes the nanoparticles impure and potentially hazardous for the human body. “With lasers we can create pure nanoparticles, and our model can be used to study the process of its formation as a function of various laser parameters,” says Igor.
Figure 1. Evolution of the Ru-on-substrate target irradiated with a 100 fs XUV laser pulse
One of the big achievements during the PhD was to find the right experts and combine all their work together. “Everything I did was only possible thanks to our extensive network of academic institutes and industrial partners. The topic is very multidisciplinary with optics, thermodynamics, atomic- and laser physics interplaying on various timescales,” says Igor.
Dr Igor Milov now works on the X-tools project as a PostDoc for the XUV Optics group at the faculty of Science and Technology. For the defence of his PhD thesis titled Damage processes in ruthenium thin films induced by ultrashort laser pulses, Igor has been awarded a cum laude degree. His research, also done in the XUV Optics group was supervised by professor Fred Bijkerk and was part of the MiLiMiD project.