E. I. Ageev

Controlled oxide films formation by nanosecond laser pulses for color marking

A technology of laser-induced coloration of metals by surface oxidation is demonstrated. Each color of the oxide film corresponds to a technologic chromacity coefficient, which takes into account the temperature of the sample after exposure by sequence of laser pulses with nanosecond duration and effective time of action. The coefficient can be used for the calculation of laser exposure regimes for the development of a specific color on the metal. A correlation between the composition of the films obtained on the surface of stainless steel AISI 304 and commercial titanium Grade 2 and its color and chromacity coordinates is shown.

Non-contact ultrasonic acquisition of femtosecond laser-driven ablative Mbar-level shock waves on Ti alloy surface

Mbar-level ablative plume pressures, produced by single-shot femtosecond laserablation of a dry Ti alloy surface and driving shock waves in air and in the solid target, were characterized using non-contact broad-band ultrasonic measurements. X-ray diffraction measurements reveal the resulting shock-wave induced sub-GPa residual compressive stresses over multi-micrometer depths inside the target, indicating GPa-level residual compressive stresses on its surface.

Double-pulse femtosecond laser ablation of the surface of stainless steel with variable interpulse delays

Spectral studies of optical emission from plumes produced via ablation of the surface of stainless steel in the phase explosion regime at different incident fluences by a pair of collinear degenerate femtosecond laser pulses, separated by variable delay time of 0.01–1.5 ns, demonstrate a drastic decrease in atomic emission intensities in a subnanosecond range. This effect was related to “bulk” absorption of the second pump pulse in ablative plumes with near-critical density, achieved during their hydrodynamic expansion on a subnanosecond timescale.

3D express crystallization of Foturan glass at CO2 laser annealing on defects produced by picosecond laser

Laser-induced crystallization in the volume of plates of Foturan™ photosensitive glass (PG) at heat treatment under the CO2-laser radiation on previously produced microdefects is considered. Processes of a crystal phase nucleation and growth during exposure of PG plate by CO2-laser are investigated. Comparison of heat treatment conditions of PG plate under furnace heating and when exposed to irradiation of CO2-laser is made.

Contact and non-contact ultrasonic diagnostics of shock waves driven by single-shot femtosecond laser ablation of titanium

Initial pressures and expansion speeds of air shock waves, driven by single-shot femtosecond laser ablation of titanium surface at fluences up to 6 J/cm2, were acquired by means of front-side non-contact time-of-flight ultrasonic measurements. Similar contact ultrasonic measurements on the rear side of the titanium target demonstrate general correlation of ultrasonic amplitudes the measured in the contact and non-contact modes at high ablative pressures (above 100 GPa, superelastic propagation regime), and strong deviation of these dependences at lower ablative pressures (strong dissipation regime) without any indications of new titanium phases, besides the initial α-Ti phase.

Modification of photosensitive glass-ceramic Foturan by ultrashort laser pulses

In this paper laser-induced modification of photosensitive glass-ceramic materials under YAG:Nd second harmonic picosecond pulses is observed. The method for such modification based on laser processing and subsequent heat treatment is developed. The comparison for infrared femtosecond modification is introduced.

Double-pulse femtosecond laser peening of aluminum alloy AA5038: Effect of inter-pulse delay on transient optical plume emission and final surface micro-hardness

Double-pulse ablative femtosecond laser peening of the AA5038 aluminum alloy surface in the phase explosion regime results in its enhanced microhardness, which monotonously decreases till the initial value versus inter-pulse delay, increasing on a sub-nanosecond timescale. Optical emission spectroscopy of the double-pulse ablative plume reveals the same trend in the yield of the corresponding atomic and ion emission versus inter-pulse delay, enlightening the interaction of the second femtosecond laser pump pulse with the surface and the resulting plume.