This article focuses on generation of diffractive optical elements (DOEs) and computer holograms for forming three-dimensional (3D) images. We intend to analyze the possibilities of increasing (1) the speed of generation of DOEs, and (2) the quality of 3D objects created by the DOEs generated. For this, four methods of optical element generation are analyzed, which are based on division of 3D objects into plane layers. We assess the quality of 3D-object image reconstruction and the resource intensity of the methods with respect to synthesis of DOEs. We conduct a computer simulation of reconstruction of images of 3D objects via the generated DOEs. In optical experiments on formation of 3D objects, the DOEs generated are displayed on a liquid crystal spatial light modulator. We experimentally establish that the method of parallel computation of plane layers and the method of nonconvex optimization are optimum for formation of 3D objects vis-à-vis quality of their reconstruction. Taking into account the computational resource intensity of the considered methods, the iterative method of parallel computation of plane layers yielded the optimal DOE generation results in terms of reconstruction quality-to-synthesis speed ratio. The possibility of fast formation of high-quality 3D objects comprising dozens of layers has been demonstrated, which can be used in high-resolution 3D video communication systems.

The article is devoted to the generation of diffractive optical elements and computer holograms for forming three-dimensional images. Possibilities of increasing the speed of diffractive optical elements generation and the quality of reconstructed 3D-objects were investigated. Four methods of optical elements generation were analyzed. The methods use division the 3D-objects into fl at layers. The quality of 3D-object reconstruction and time generation by the methods were assessed. 3D-object reconstruction from generated optical elements was modeled. Optical formation of objects was performed by displaying optical elements onto liquid crystal spatial light modulator. It was found that the best quality of reconstruction was provided by iterative parallel ping-pong and non-convex optimization methods. The optimal ratio of reconstruction quality to generation speed ratio was obtained for the parallel ping-pong method. The possibility of fast formation high-quality three-dimensional scenes consisting of dozens of layers has been demonstrated.

An apparatus for studying the processes of laser action on various materials, including biological tissue, is described. The system makes it possible to obtain thermograms of the sample surface, conduct high-speed video recording, and record acoustic signals in a wide frequency range during experiments. The system was tested using a pulsed nanosecond high-frequency laser source with a wavelength of 3.03 μm. The samples were exposed to pulses with a duration of 1.5 ns and a frequency of 8 MHz. It is shown that it is possible to use a laser system to obtain incisions on biological tissues of various types without carbonization. The obtained experimental data made it possible to clarify the mechanism of the action of laser radiation on the surface of water-saturated biological tissues.

The application of spheroids in tissue engineering has a number of advantages over conventional cell suspensions and 2D cultures. One of the methods for tissue and organ fabrication from spheroids is bioprinting. As one of bioprinting methods, laser-induced forward transfer (LIFT) has received much attention in terms of cell printing, while its potential has not been realized for spheroid patterning yet. In this paper, the authors have shown for the first time the practical applicability of LIFT for spheroid transfer with high survival rates and printing precision. For this, a special optical device, a piShaper, was used to change the laser energy distribution to non-Gaussian profile which allowed for mitigating the negative effects of laser radiation on the spheroids during LIFT. The authors showed that non-Gaussian energy distribution in the laser spot in the form of double ring led to higher post-printing viability of spheroids than in case of conventional Gaussian energy distribution in laser beam. Subsequently, using the double ring laser spot geometry, the spheroids were bioprinted in the form of simple geometric figures: line, triangle, and square. Overall, LIFT bioprinting of spheroids has demonstrated a strong potential as the precise, safe, and reproducible method for biofabrication that can be potentially used for making tissue-engineered bioequivalents or building specific organ-on-a-chip platforms.

Surface-selective laser sintering (SSLS) is a specific version of selective laser sintering, which allows one to fabricate 3D structures with well-defined architectonic via selective melting of microparticle surface without alteration of their core. This mode of laser sintering requires a well-designed surface properties of the microparticles to adsorb laser irradiation. Water was chosen as safer sensitive absorber of laser radiation with a wavelength of 1.9 μm, i.e. one with low absorption coefficient by polymeric core. Biodegradable polylactide microparticles were fabricated via oil/water emulsion solvent evaporation technique using tailored-made chitosan-based macromolecules, which provided the effective interface stabilization during the microparticle fabrication and well balanced microparticle surface hydrophilicity to adsorb water. Especially build SSLS set-up was designed in order to monitor the effectiveness of the 3D scaffold fabrication from the obtained microparticles and to adapt the optimal laser radiation parameters with a wavelength of 1.9 μm (e.g. speed, line density, power).

The influence of mid-IR (1.94 μm) laser radiation on the morphology of polylactide and polycaprolactone nonwoven materials obtained by electrospinning has been revealed. It has been shown that laser irradiation makes it possible to achieve local structuring of the nonwovens at the micrometer level, in particular, to fuse individual fibers, straighten them between fusion points, and prepare monolithic films from the materials or, conversely, create breaks in them. The influence of laser irradiation parameters (power, laser spot speed, scan line density) and additional wetting of the samples on the structure of the nonwovens has been determined.