Experimental investigations of the absorption of laser radiation in the optical discharge when placed in the laser cavity were conducted. A significant increase in the absorption until complete absorption was established. An optical schemes of the initiation and maintenance of the optical discharge in the cavity are proposed, which greatly extends the field of application of optical discharge in technology.
Under full temperature monitoring investigation of the melting of overhang layers has been conducted. Mechanisms of the melt penetration into loose powder bed have been determined. Also temperature regimes of the selective laser melting process of the 3D object from steel 316L powder were investigated.
The principles of measuring the surface temperature of powder bed in the focal spot of the laser radiation while scanning
the surface using galvoscanner with F-teta lens have been elaborated. Investigation of the melting of overhang layers
has been conducted under full temperature monitoring. Temperature regimes of the selective laser melting process of the
3D object from steel 316L powder have been investigated.
The optical systems for temperature monitoring of SLS/SLM process are developed and integrated with industrial
SLS/SLM machines. The system provides the possibility to spatial distribution of brightness temperature at two
wavelengths and selected temperature profiles, calculation of colour temperature and express analysis of possible
deviations of the maximum temperature from its optimal value. Optimal regimes of SLS process for the sintering of the
high porosity powder body was determined.
Some optical schemes for the production of conical beams with high cone angle and a quasi-uniform axial distribution of
the intensity have designed and a elaborated method of laser power delivery in heterogeneous stream are used for
nanopowder production and SLC process modification. The new principles of laser pulse generation are elaborated
and optical schemes for production of a volumetric laser beams, convergent spherical and cylindrical have been
designed. On the base of laser system developed and concept of quasitransparent first wall the reactor construction
design intent has been proposed.
The results of investigations of metal surface destruction , plasma formation and evolution on exposure to quasicontinuous
pulsed laser under high pressure (up to 1.6 MPa) of ambient nitrogen are presented.
Temperature monitoring in the laser impact zone is carried out by an originally developed bi-colour pyrometer which is
integrated with the optical scanning system of the PHENIX PM-100 machine.
Experiments are performed with variation of basic process parameters such as powder layer thickness (0-120μm), hatch
distance (60μm-1000μm), and fabrication strategy (the so-called "one-zone" and "two-zone").
Near-infrared spectroscopy has been widely used to determine the oxygenation of cerebral tissue. New
technology of cerebral oxygenation measurements based on time resolved registration of backscattered radiation of probing picosecond laser pulse are considered.
The Q- switched laser system for short pulse laser beam generation are presented. Through the creation of required
configuration of photon field at short cavity using external cavity short and intensive laser pulse is generated. The
investigations of spatial characteristics of laser field in the center of the converging beams are carried out.
Thermal and hydrodynamic processes in layer of metals on exposure to pulsed heating by laser radiation ensemble of
pores, gas filling of which occur due to the desorption of gas layers, covering the porous wall are considered. The
temperature, stress and plastic strain fields dynamics inside the samples were investigated. Shown that for materials
with melt temperature T<sub>melt</sub>> 2000 K the pore structure explosion is quite possible at solid state with particles release.
A brief overview of currently available methods applied in laser synthesis of 3D parts is presented, which range from stereolithography making use of liquid photopolymers to selective laser sintering of metal powders aimed at production of the parts of complex topology.
To control the process parameter settings and to visually inspect the process quality, a monitoring system for the
sintering process was designed. The monitoring of the sintering process is based on measurements of the maximum
surface temperature and the temperature distribution at the sintering zone by the spectral ratio method. Software and
hardware for adaptive process control of powder solids SLS were developed.
The new design of Q-switched disk laser are presented. Through the creation of required configuration of photon field at
resonator using external resonator the short and intensive laser pulse is generated. The investigations of spatial and
temporal characteristics of laser field in laser are carried out.
The Q- switched laser systems for pulsed volumetric laser beam generation are presented. Through the creation of
required configuration of photon field at resonator using external resonator the short and intensive cylindrical and
spherical converging laser pulse is generated. The investigations of spatial characteristics of laser field in the center of
the converging beams are carried out.
The new approach to laser powder sintering and 3D-forming based on Bessel laser beams is presented. The results of calculations of powder stream impact on Bessel beam parameters and powder particles and base heating is displayed.
The results of a complex study of the ablation of metals when they are acted on by radiation pulses 40-300 ns wide from neodymium laser are presented. Low-thresholds surface ablation has been detected in a number of metals at surface temperatures below the boiling point, before the instant plasma formation, with a burst of particles of the condensed disperse phase and the formation of microstructures with a characteristics size of 1-10 micrometers . A description is given of the laser-induced ablation model, based on the purely thermal action of laser radiation and the natural inhomogeneity of solids.
As a result of experiments and numerical simulation low- threshold ablation of materials under the action of pulsed laser radiation on metals was established. The resulting surface structure with heat insulating fragments contribute to low-threshold evaporation and erosion plasma ignition. Analysis of experimental data on plasma threshold conditions in the wide range of wavelengths and laser pulse lengths has been carried out.
Appearance on the surface of metals of microcraters, microparticles, and continuity breaks with characteristics sizes 1 - 10 micrometer was experimentally observed under the action of laser monopulses of duration 40 ns and 300 ns. The model of initial destruction of materials and generation of condensed particles based on exclusively thermal action of laser radiation and natural inhomogeneity of solids is developed.