A.A. Serkov

Temporal and Spectral Characterization of Breakdown Plasma Induced by Laser Radiation in Colloidal Solutions of Gold Nanoparticles

Temporal and spectral characteristics of laser-induced breakdown plasma in colloidal solutions of gold nanoparticles were experimentally studied. Near-infrared laser sources of nanosecond pulses were used. It was shown that under certain experimental conditions nanosized plasma around nanoparticles might change to laser-induced breakdown plasma in liquid. The dependencies of the plasma temporal and spectral characteristics on laser pulse duration as well as resulting nanoparticles properties were studied. Laser-induced breakdown plasma lifetime was shown to be comparable with laser pulse duration. The efficiency of gold nanoparticles fragmentation was shown to depend on laser pulse duration. Similar experiments were carried out under reduced external pressure. It turned out to affect the properties of both plasma plume and nanoparticles. Transmission electron microscopy and disc measuring centrifuge were used for nanoparticle morphology and size analysis. Extinction spectra of colloidal solutions and emission spectra of plasma were studied by means of optical spectroscopy.

Influence of laser-induced breakdown on the fragmentation of gold nanoparticles in water

The process of fragmentation of gold nanoparticles in water exposed to nanosecond IR laser radiation (1060 – 1070 nm) is studied. The behaviour of the size distribution and extinction spectrum of nanoparticles is investigated at different experimental parameters. The dependences of the size distribution maximum position and distribution width on the laser pulse duration and the corresponding characteristics of the laser plasma, arising on the nanoparticles, are analysed. The results are explained by the plasma influence on the laser radiation absorption by the colloidal solution.

Nanostructuring of single-crystal silicon carbide by femtosecond laser irradiation in a liquid

The formation of nanostructures on the surface of single-crystal silicon carbide under ablation by femtosecond laser pulses in liquid ethanol has been experimentally investigated. A 800-nm Ti:sapphire laser with a pulse duration of 210 fs was used as a radiation source. Single-scan irradiation of SiC surface leads to the formation of periodic grooves with a period of about 200 nm. Double exposure with a sample rotation by 90° between the scans gives rise to a regular array of nanostructures with average lateral size of 10 to 15 nm. It is determined that the wettability of nanostructured SiC surface is improved in comparison with the initial surface. It is shown that nanostructuring of SiC surface leads to an increase in the red light transmission by a factor of more than 60.

Fabrication of Materials with Low Optical Reflectance Based on Laser-Microstructured Metal Surfaces

It has experimentally been shown that the specular reflectance of some metals can be reduced by one to two orders of magnitude by subjecting them to multipulse laser ablation in air. An increase in the coefficient of grayness has been implemented for copper, nickel, aluminum, and stainless steel. Multipulse ablation of the corresponding targets leads to the formation of a quasi-periodic microstructure with an amplitude relief ranging from 30 to 50 μm. The specular reflectance of duralumin has been reduced using anodic oxidation of the microstructures formed by laser ablation and filling the newly formed pores with carbon nanoparticles. The thus obtained surfaces are close to ideal black body in their optical characteristics.