One of the key challenges in material laser processing is extending the technological limits in controllable modification of material properties down to nanometer scale. Surfaces of different materials, being modified with creation of nanoscale structures, possess unique electronic, optical, mechanical, and catalytic properties. Achieving the control over laser production of such functional surfaces at low cost would lead to tremendous progress in information technologies, health care, public security, and smart energy solutions. However, the trial-and-error approach based on repeated attempts until success, which are usually used for optimization of laser surface processing is inefficient. In-depth understanding of the underlying physics of laser-induced surface modification can push this field from empirical methods to a smart computer-predicting technique. This can be realized via developing adequate theoretical models of laser-induced phenomena in solids, which is the aim of this ambitious project.
The EU funded project “Quantum effects in multicolor ultrafast laser processing: broadening boundaries of classical descriptions” (QuantumLaP) was focused on the interaction of ultrashort laser pulses with semiconductors (in the first turn, with silicon as one of the most demanded materials in real-life applications). It aimed at investigating laser-induced processes based on a new approach by taking into account quantum effects, which can influence the behavior of laser-irradiated materials. The impact of quantum phenomena on laser-induced dynamics of material excitation was studied for mono- and bi-chromatic irradiation regimes; the latter can be more efficient for various applications, compared to monochromatic light. The final goal was the development of a predictive model for material functionalization, allowing a fast assessment of final morphology of laser-treated surfaces.
To achieve the project goals, two models have been developed, a quantum-level, first-principles model describing the action of mono- and bi-chromatic laser light on semiconductors and a continuum model for direct comparison with quantum simulations. This enabled to verify and improve the existing theory of photoionization of solids. Furthermore, quantum simulations overturned existing concepts of bandgap material photoionization via insight into temporal dynamics of free charge-carrier excitation.
Finally, a predictive theory of laser-induced periodic surface structure (LIPSS) formation was developed, which explains the LIPSS regularities on different materials and enables selection of materials for ultrafast fabrication of high-regular structures. A numerical code developed for calculations of the LIPSS regularity can be accessed by external users. A database on the LIPSS regularities has been created for more than 60 materials and their combinations, opening ways for synthesis of new plasmonic materials, which could be cheaper than presently existing ones.
QuantumLaP successfully led to broadening the available knowledge on ultrafast laser excitation of bandgap materials. Project findings are opening new opportunities for advanced fabrication of functional surfaces with nanofeatures.
