Improvement of Thermochemical Processes of Laser-Matter Interaction and Optical Systems for Wavefront Shaping

Abstract

Laser thermochemical processes of metal surface oxidation are promising for creating new advanced technologies to meet the growing needs of opto- and micro-electronics, photonics, catalysis, sensorics and other high-tech industries. The features of thermochemical processes of laser-matter interaction occurring in matter under exposure to intense light flows and optical systems for controlling the irradiance and wavefront spatial distribution were reviewed. The laser beam offers the possibility of good focusing, which allows us to conduct chemical reactions, including the heterogeneous oxidation of metals, locally, with high spatial resolution. In this case, the absorption mechanisms of the laser beam vary for metals and for oxides, resulting from a thermochemical reaction and represent semiconductors. For semiconductors, the intrinsic, intraband, impurity, or lattice absorption takes place. The morphology of a metal surface also influences its optical absorption capacity. The improvement of beam shaping systems with elements of computer optics, namely diffractive freeform optics, provides an opportunity for an efficient control of chemical processes by achieving the desired redistribution of the laser beam power density. Laser thermochemical processes of the formation of quasi-one-dimensional nanostructured metal oxides are of great interest for advanced research and for a wide range of applications. A special feature of these processes is that, in the case of a frequency-modulated laser beam the synergy between the heat associated effects of the laser pulses and the laser-induced vibrations allows for a significant increase in the diffusion coefficient, which is stimulated by the non-stationary stress-strain state of the material. Ensuring the means of control over the thermochemical reaction in local sections of the laser exposure zone is an issue that can be solved by adapting the shape of the laser beam by the diffractive freeform optics. The gained knowledge contributes as a foundation for new photonic technologies oriented on the formation of nanostructured metal oxides, involving control over the morphology of the synthesized structures.