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Photothermal therapy (PTT) has attracted increasing interest as a complementary method to be used alongside conventional therapies. Despite a great number of studies in this field, only a few have explored how temperatures affect the outcome of the PTT at nanoscale. In this work, we study the necrosis/apoptosis process of cancerous cells that occurs during PTT, using a combination of local laser heating and nanoscale fluorescence thermometry techniques. The temperature distribution within a whole cell was evaluated using fluorescence lifetime imaging microscopy during laser-induced hyperthermia. For this, gold nanorods were utilized as nanoheaters. The local near-infrared laser illumination produces a temperature gradient across the cells, which is precisely measured by nanoscale thermometry. This allows one to optimize the PTT conditions by varying concentration of gold nanorods associated with cells and laser power density. During the PTT procedure, such an approach enables an accurate determination of the percentages of apoptotic and necrotic cells using 2D and 3D models. According to the performed cell experiments, the influence of temperature increase during the PTT on cell death mechanisms has been verified and determined. Our investigations can improve the understanding of the PTT mechanisms and increase its therapeutic efficiency while avoiding any side effects.

The transmission of near infrared femtosecond laser pulses (wavelength of 800 nm) and supercontinuum radiation (300–750 nm) generated by them through a 50-nm gold film immersed in water has been experimentally studied at the power of focused laser radiation in the range of 1–10 GW. An increase in the excitation intensity is accompanied by the blueshift of the edge of the extinction band of the film, which is attributed to the filling of electronic states of the s band with a low density of states caused by two-photon interband transitions from d bands with a high density of states.

The introduction of a small amount of subwavelength gold nanoparticles (extinction coefficient ∼0.01–1 cm−1) to water allows the efficient control of filamentation owing to nonlinear dissipative losses of a primary ultrashort pump laser pulse and secondary broadband radiation (supercontinuum), because the intrinsic extinction coefficient in the multiple filamentation regime is below 0.04 cm−1. Optical emission and photoacoustic spectroscopy studies have shown that an increase in losses in a colloidal solution sublinearly increases the power of an ultrashort laser pulse for the nonlinear generation of supercontinuum with the same intensity, and it also increases the filamentation threshold near the supercontinuum generation threshold. At the same time, supercontinuum emission is significantly enhanced in the region of plasmon resonance of nanoparticles against the background of broadband nonlinear absorption. The results demonstrate new possibilities of controlling the nonlinear optical characteristics of media for the generation and filamentation of ultrashort light pulses in various spectral ranges.

The generation of supercontinuum radiation at the filamentation of femtosecond laser pulses (800 nm) with a supercritical gigawatt peak power in pure water and colloidal solutions of plasmon gold nanoparticles (perturbative regime) has been studied experimentally. After correction to the extinction of the fluid behind a filament, the supercontinuum radiation yields from the active filamentation zone in water (broadband radiation source) and in colloidal solution (broadband radiation source modified by various in situ interactions with nanoparticles) have been compared and analyzed for various peak radiation powers. As a result, the proposed method of ultrafast broadband nonlinear spectroscopy has allowed the observation of effects of the saturated two-photon interband absorption of gold nanoparticles in the spectral range of supercontinuum generation and the enhancement of this generation in the range of plasmon resonance of nanoparticles.

Single-shot nanosecond laser ablation of stainless steel and copper surfaces in ambient air and liquid water environment was studied by contact broadband ultrasonics in the important laser intensity range of 6–450 GW/cm2, covering both regimes of surface phase explosion and formation of sub-critical ablative plasma via optical breakdown in the corresponding dense ablative plume. Similar dependences of ablative plasma pressure were obtained for the dry and wet ablation conditions, differing in their ultrasonic pulse amplitudes by the factor ∼5 and in their pulsewidths by the factor of 1.3 (copper) and 1.6 (steel) for the wet ablation because of the dynamic water-confinement effect. Excepting the confinement effect, these results indicate the similar conditions for pressure generation via sub-critical plasma formation both for the air and water environments, enlightening promising applications of laser ablation for liquid-assisted laser peening and generation of nanoparticles in liquids.

International audience; The paper investigates how the surface relief of an implant affects cell behavior. Currently, most implant manufacturers claim the key impact biocompatibility factor to be surface micro-roughness. We suppose that the interaction between cells and implants also depends on such relief peculiarities as continuous or discontinuous topography, subcellular distance between peaks and presence of porous oxide layer. We have developed the laser processing conditions that provide three different reliefs: «open grooves», «grid» and «close grooves». Along with the micro-roughness characteristics the reliefs differ with their deepness and period of grooves. The surface composition analysis results have shown a sandwich structure consisting of Ti → TiO → Ti 2 O 3 Nx → TiO 2 (anatase) → TiO 2 (rutile). The wettability study has demonstrated superhydrophilicity (CA is 0 •) for all reliefs. The quantitative and qualitative analysis of hMSCs proliferation and osteogenic differentiation was performed for 20 days. In vitro study has revealed the topography affects the spatial orientation of cells. The shape and size of the cell nuclei vary with different topographies. We have found continuous «open grooves» structures with the subcellular to cellular period are beneficial for cells' life-sustaining activity. Discontinuous «grid» structures with individual slots might not provide cells with mobility with the least external mechanical effect compared to «open grooves».

Laser direct writing technique in glass is a powerful tool for various waveguides&rsquo, fabrication that highly develop the element base for designing photonic devices. We apply this technique to fabricate waveguides in porous glass (PG). Nanoporous optical materials for the inscription can elevate the sensing ability of such waveguides to higher standards. The waveguides were fabricated by a single-scan approach with femtosecond laser pulses in the densification mode, which resulted in the formation of a core and cladding. Experimental studies revealed three types of waveguides and quantified the refractive index contrast (up to &Delta, n = 1.2&middot, 10&minus, 2) accompanied with ~1.2 dB/cm insertion losses. The waveguides demonstrated the sensitivity to small objects captured by the nanoporous framework. We noticed that the deposited ethanol molecules (3 &micro, L) on the PG surface influence the waveguide optical properties indicating the penetration of the molecule to its cladding. Continuous monitoring of the output near field intensity distribution allowed us to determine the response time (6 s) of the waveguide buried at 400 &micro, m below the glass surface. We found that the minimum distinguishable change of the refractive index contrast is 2 &times, 4. The results obtained pave the way to consider the waveguides inscribed into PG as primary transducers for sensor applications.

In this work, we suggest the new concept of sensing elements&mdash, bulk waveguides (BWGs) fabricated by the laser direct writing technique inside porous glass (PG). BWGs in nanoporous materials are promising to be applied in the photonics and sensors industries. Such light-guiding components interrogate the internal conditions of nanoporous materials and are able to detect chemical or physical reactions occurring inside nanopores especially with small molecules, which represent a separate class for sensing technologies. After the writing step, PG plates are impregnated with the indicator&mdash, rhodamine 6G&mdash, which penetrates through the nanoporous framework to the BWG cladding. The experimental investigation proved the concept by measuring the spectral characteristics of an output signal. We have demonstrated that the BWG is sensitive to ethanol molecules captured by the nanoporous framework. The sensitivity of the peak shift in the fluorescence spectrum to the refractive index of the solution is quantified as 6250 &plusmn, 150 nm/RIU.

We present a new approach to femtosecond direct laser writing lithography to pattern nanocavities in ferromagnetic thin films. To demonstrate the concept we irradiated 300~nm thin nickel films by single intense femtosecond laser pulses through the glass substrate and created complex surface landscapes at the nickel-air interface. Using a fluence above the ablation threshold the process is destructive and irradiation leads to the formation of 200~nm thin flakes of nickel around the ablation crater as seen by electron microscopy. By progressively lowering the peak laser fluence, slightly below the ablation threshold the formation of closed spallation cavities is demonstrated by interferometric microscopy. Systematic studies by electron and optical interferometric microscopies enabled us to gain an understanding of the thermo-mechanical mechanism leading to spallation at the solid-molten interface, a conclusion supported by molecular dynamics simulations. We achieved a control of the spallation process that enabled the fabrication of closed spallation nanocavities and their periodic arrangements. Due to their topology closed magnetic nanocavities can support unique couplings of multiple excitations (magnetic, optical, acoustic, spintronic). Thereby, they offer a unique physics playground, before unavailable, for magnetism, magneto-photonic and magneto-acoustic applications., 4 figures

Laser-induced periodic surface structures (LIPSSs) spontaneously appearing on the laser-treated (melted or evaporated) surfaces of bulk solid materials seem to be a well-studied phenomenon. Peculiarities of oxidative mechanisms of LIPSS formation on thin films though are far less clear. In this work, the appearance of oxidative LIPSSs on thin titanium films was demonstrated under the action of commercially available nanosecond-pulsed Yb-fiber laser. The temperature and energy regimes favoring their formation were revealed, and their geometric characteristics were determined. The period of these LIPSSs was found to be about 0.7 &lambda, while the modulation depth varied between 70 and 110 nm, with high stability and reproducibility. It was shown that LIPSS orientation is rather easily manageable in the regimes of our interest, which could provide a way of controlling their properties.

International audience; Modern methods of laser-based nanocomposite fabrication and treatment rely on a deep understanding of the interplay between a set of mechanisms involved, such as nanoparticle growth and decay, material phase transformation, degradation, and damage. In this work, scanning multipulse femtosecond laser irradiation is used for Au:TiO 2 nanocomposite formation. Depending on laser scan speed, two different regimes are observed revealing different gold nanoparticle growth rates. The regime of the remarkably fast laser-induced growth of Au nanoparticles is found to be accompanied by the cavity formation in titania film around the particles. The transition between two formation regimes is found to be abrupt, confirming the catastrophic mechanism of Au nanoparticle growth. The obtained results are analyzed based on the developed numerical model including effects such as nanoparticle absorption, local field enhancement, photoinduced free carrier generation, plasmon-assisted electron emission, and thermal heat transfer from nanoparticles toward titania matrix. Our modeling reveals the crucial role of collective thermoplasmonic effects caused namely by bimodal nanoparticle size distribution. The performed analysis also suggests that spall in the solid state is responsible for final matrix degradation if nanoparticles become large enough. The considered laser-based formation of optical nanocomposites is crucial not only for the better understanding of ultrashort laser interactions with glass− metallic nanocomposite materials but also for numerous applications in photocatalysts, solar cells, and chemosensors.

In this work, a new domain of femtosecond laser-induced densification was exploited as a method for space-selective control of porous glass matrix density. The estimated refractive index change (Δn) of laser-induced modified region shows a core-cladding structure with the Δn in the range of 10−4–10−2 depending on laser pulse energy and translating speed. The approximate linear relationship between glass matrix density vs Δn is theoretically proved by employing the Lorentz–Lorenz equation. Thus, the positive and negative Δn of modified region are interpreted as the densification and rarefaction of glass matrix, respectively.

The possibility of creating physical barriers with various degrees of permeability in porous glass (PG) plates by local variation in the density of the porous structure of the matrix is demonstrated. The compaction of PG in the volume is provided by exposure to femtosecond laser pulses, while the surface impermeability of the compaction areas is provided by exposure to radiation of the CO2 laser. This approach to control the density of the PG structure makes it possible to create molecular barriers that represent a physical and/or chemical boundary for molecules located in a porous matrix (with controlled permeability). The discussed technology of the local porosity control opens the way to designing integral photon, fluid, and other types of devices based on PG plates.

Recent research in the field of formation of a 3D profile of optical elements with the use of direct laser writing at various wavelengths and photolithographic technologies on the basis of photomasks fabricated by means of laser writing is reviewed. Typical characteristics of the relief, as well as advantages and drawbacks of the above-mentioned methods are considered.

A technique for the laser coloration of precious metals is described that is based on the oxidation of a titanium film deposited on the surface of a metal. When laser radiation acts on the film, it is heated and oxidizes. Depending on the radiation parameters, the resulting oxide films have different thicknesses and, due to light interference, they acquire different colors. The visible color of the surface depends on the angle of viewing after imaging. The aim of this work is to identify the color palette of a gold plate’s surface with a thin film of titanium deposited on it. The titanium film is oxidized via fiber laser irradiation with a wavelength of 1.064 μm. Samples of color palettes are examined spectrophotometrically, and the chemical and mechanical stability of the resulting oxide coatings are tested.

We have studied the properties of laser-induced microplasma (LIMP) emerging in the ablation of a strongly light-absorbing target in the regime of confinement of spatial plasma expansion. The LIMP particle temperature is shown to be higher in this case than in the free expansion. It is found that the amplitude of the pressure pulse in the regime of spatial LIMP confinement is an order of magnitude higher than in the open surface case. The feasibility of writing microstructures on transparent dielectrics with the use of LIMP is demonstrated: microlens arrays and different diffraction elements are made.

This paper is a review of studies carried out by the staff of the National Research University of Information Technologies, Mechanics and Optics (ITMO University, Saint-Petersburg) and the Institute of Automation and Electrometry of the Siberian Branch of the Russian Academy of Sciences (IAE SB RAS, Novosibirsk) in the field of development of laser engineering processes for the formation of the structure of diffractive optical elements (DOEs) and photomasks with amplitude binary and grayscale transmission. This paper also describes the results of the study of laser thermochemical technology for fabricating chrome DOEs and technologies for the fabrication of grayscale DOEs and photomasks based on the use of amorphous silicon and LDW glass.

High-pressure Si-XII and Si-III nanocrystalline polymorphs, as well as amorphous Si phase, appear consequently during multi-shot femtosecond-laser exposure of crystalline Si wafer surface above its spallation threshold along with permanently developing quasi-regular surface texture (ripples, microcones), residual hydrostatic stresses and subsurface damage, which are characterized by scanning and transmission electron microscopy, as well as by Raman micro-spectroscopy. The consequent yields of these structural Si phases indicate not only their spatially different appearance, but also potentially enable to track nanoscale, transient laser-induced high-pressure, high-temperature physical processes – local variation of ablation mechanism and rate, pressurization/pressure release, melting/resolidification, amorphization, annealing – versus cumulative laser exposure and the related development of the surface topography.

In this work, we studied a method of laser-induced coloration of metals, where small-scale spatially periodic structures play a key role in the process of color formation. The formation of such structures on a surface of AISI 304 stainless steel was demonstrated for the 1.06 µm fiber laser with nanosecond duration of pulses and random (elliptical) polarization. The color of the surface depends on the period, height and orientation of periodic surface structures. Adjustment of the polarization of the laser radiation or change of laser incidence angle can be used to control the orientation of the structures. The formation of markings that change their color under the different viewing angles becomes possible. The potential application of the method is metal product protection against falsification.

In this work, we studied a technology of color images formation on a surface of titanium film deposited on silver and gold substrates. The coloration takes place due to film oxidation by the action of a fiber laser with nanosecond duration of pulses. Color coordinates for main colors obtained on gold and silver surfaces were calculated. According to measured reflectance spectra the final color resulted from both interference effects in the thin oxide film and substrate optical properties. Mechanical and chemical resistance tests of formed images demonstrated a high degree of adhesion between deposited titanium film and precious metals. Therefore, the proposed technology has a strong potential for jewelry industry implementation.

Interference of laser beams with high pulse energy opens an opportunity of direct oxidation of surfaces over large areas. It is important to confirm that the single ultrashort laser pulse irradiation is able to create the protective oxide layer on chromium films. Here, we report an approach of hybrid thermo-chemical treatment of thin chromium films irradiated by laser beam interference utilising picosecond and nanosecond laser pulses combined with the subsequent chemical etching. The array of periodical structures with a period of 1.5–3.5 μm and array size of 300 × 300 μm 2 were created on the chromium film. Theoretical modelling combining the laser heating of a thin film by the multi-beam interference and growth of the oxide layer is discussed. Confirmed thermo-chemical microstructuring of thin metal films using multi-beam interference opens the opportunities in fabrication of low-cost and high-quality diffractive optical elements.

Products formed in laser ablation of single-crystal silicon beneath a water layer under irradiation with nanosecond pulses from a fiber-optic ytterbium laser have been studied. SEM images of structures deposited by dewatering of the colloid solution formed in the course of the ablation are presented. IR spectroscopy and Raman spectroscopy were used to determine their chemical composition and structural features.

The laser oxidation of thin metallic films followed by its selective chemical etching is a promising method for the formation of binary metal structures on the glass substrates. It is important to confirm that even a single ultrashort laser pulse irradiation is able to create the protective oxide layer that makes possible to imprint the thermochemical image. Results of the thermo-chemical treatment of thin chromium films irradiated by picosecond laser pulse utilizing two and four beam interference combined with the chemical etching are presented. The spatial resolution of this method can be high enough due to thermo-chemical sharpening and can be close to the diffraction limit. Micro-Raman spectroscopy was applied for characterization of the chemical composition of the protective oxide layers formed under atmospheric conditions on the surface of thin chromium films.

A method for treating the surface of crystalline silicon (α-Si) covered with a fused silica (SiO2) plate by a laser-induced plume arising from the absorption of CO2 laser radiation in glass is presented. The mechanism of micro-plume formation and the effect of this micro-plume on α-Si sample are considered. The α-Si processing regimes were determined that relate the depth of the formed relief to the radiation power density, the temperature of the micro-plume formed during SiO2 irradiation was measured and reached 3000 K. The diffraction phase gratings were designed, manufactured on silicon, and tested, they successfully split 10.6 μm laser beam at 0 and ± 1 diffraction orders. The method belongs to the group of direct writing methods and is easily adapted to different types of diffraction elements on the surface of Si and other materials transparent to 10 μm irradiation.

Laser thermochemical recording is a flexible method for direct writing the binary planar structures (for instance, diffractive optical elements) by a local laser-induced oxidation of thin metal films. Unfortunately, due to excess of influencing parameters, search for regimes of high-resoluted recording could be complicated. The presented article proposes the way to analyze the hard-to-reach regimes of laser recording by modeling them with more convenient regimes (with different geometric and/or thermochemical parameters) based on their physical similarity.

A comprehensive picture of the nanosecond-laser generation of colloidal nanoparticles in liquids is nowadays the demand of their high-throughput industrial fabrication for diverse perspective biomedical, material science, and optoelectronic applications. In this study, using silicon as an example, we present a self-consistent experimental visualization and theoretical description of key transient stages during nanosecond-laser generation of colloidal nanoparticles in liquids: plasma-mediated injection of ablated mass into the liquid and driving the vapor bubble, finalized by the colloid appearance in the liquid. The explored fundamental transient stages envision the basic temporal and spatial scales, as well as laser parameter windows, for the demanded high-throughput nanosecond-laser generation of colloidal nanoparticles in liquids.

Light is critical for art. It allows us to see color, and can itself be a tool for creating unique pieces of art and design. Here we demonstrate that a laser can be a multifunctional and effective tool for the creation of masterpieces, analogous to the process of an artist creating a canvas with classical paints and brushes. We investigate the interaction between focused laser irradiation and metallic surfaces and analyze the optical effects in thin oxide films for three main artistic operations: color making, multiple color changes, and erasing managed by a nanosecond laser. These processes are possible upon heating the material above the evaporation point and are proved to be dependent on the cooling rate, according to both experimental and theoretical results. Such an interference-based laser paintbrush could find applications in modern art and design.

Fabrication of hybrid micro- and nanostructures with a strong nonlinear response is challenging and represents a great interest due to a wide range of photonic applications. Usually, such structures are produced by quite complicated and time-consuming techniques. This work demonstrates laser-induced hybrid metal-dielectric structures with strong nonlinear properties obtained by a single-step fabrication process. We determine the influence of several incident femtosecond pulses on the Au/Si bi-layer film on produced structure morphology. The created hybrid systems represent isolated nanoparticles with a height of 250–500 nm exceeding the total thickness of the Au-Si bi-layer. It is shown that fabricated hybrid nanostructures demonstrate enhancement of the SHG signal (up to two orders of magnitude) compared to the initial planar sample and a broadband photoluminescence signal (more than 200 nm in width) in the visible spectral region. We establish the correlation between nonlinear signal and phase composition provided by Raman scattering measurements. Such laser-induced structures have significant potential in optical sensing applications and can be used as components for different nanophotonic devices.

Topography-dependent tuning of water wettability was achieved on a stainless steel surface textured by nanosecond-laser pulses at different laser fluences, with the minimal contribution of the surface chemical modification. Such differently-wet neighboring surface spots were demonstrated to drive an autonomous directional water flow. A series of elementary microfluidic devices based on the spatial wetting gradients were designed and tested as building blocks of “green”, energy-saving autonomous microfluidic circuits.

Double-pulse femtosecond laser ablation of thin aluminum films and bulk aluminum counterintuitively demonstrated a strong (60–70%) raise of the thickness-dependent thresholds for inter-pulse delays of 20–200 ps, preventing material removal at above-threshold fluencies. Time-resolved optical pump-probe reflection and double-pump transmission studies were performed and confirmed the variation of the ablation threshold depending on the interpulse delay. To support the experimental measurements, the process of double-pulse laser ablation was modelled with the combined atomistic-continuum model. The applied model can describe the laser-induced non-equilibrium phase transition processes at atomic precision, whereas the effect of free carriers, playing a determinant role for the case of ultrashort laser pulses, is accounted for in the continuum. The simulations revealed the underlying pre-ablative laser-induced stress dynamics in the hot, acoustically relaxed Al melt, crucially sensitive to the second pump-pulse compressive pressurization. The results of theoretical and experimental study enable efficient dynamic all-optical control of ultrafast laser ablation.

Laser-induced thermochemical recording of nano- and microsized structures on thin films has attracted intense interest over the last few decades due to essential applications in the photonics industry. Nevertheless, the relationship between the laser parameters and the properties of the formed oxide structures, both geometrical and optical, is still implicit. In this work, direct laser interference patterning of the titanium (Ti) film in the oxidative regime was applied to form submicron periodical structures. Depending on the number of laser pulses, the regime of high contrast structures recording was observed with the maximum achievable thickness of the oxide layer. The investigation revealed high transmittance of the formed oxide layers, i.e., the contrast of recorded structures reached up to 90% in the visible range. To analyze the experimental results obtained, a theoretical model was developed based on calculations of the oxide formation dynamics. The model operates on Wagner oxidation law and the corresponding optical properties of the oxide&ndash, metal&ndash, glass substrate system changing nonlinearly after each pulse. A good agreement of the experimental results with the modeling estimations allowed us to extend the model application to other metals, specifically to those with optically transparent oxides, such as zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), and tantalum (Ta). The performed analysis highlighted the importance of choosing the correct laser parameters due to the complexity and nonlinearity of optical, thermal, and chemical processes in the metal film during its laser-induced oxidation in the air. The developed model allowed selecting the suitable temporal&ndash, energetic regimes and predicting the optical characteristics of the structures formed with an accuracy of 10%. The results are promising in terms of their implementation in the photonics industry for the production of optical converters.

Single vs multimode laser beams were compared for double pulse laser ablation, plasma properties and laser induced breakdown spectroscopy (LIBS) analytical capabilities. Laser beams with Gaussian and multimode profiles were generated within the same Nd:YAG laser in single and double pulse regimes. Gaussian beam produced a small and deep crater while multimode beam formed a wide shallow crater. Greater double pulse enhancement of ablated material and plasma volume were observed for Gaussian beam sampling. The higher intensity for atomic/ionic lines in the plasma spectra was observed for multimode beam sampling due to greater laser pulse energy and larger ablated mass. Interestingly, spectra line intensity enhancement for double pulse ablation was 2–3 times greater for Gaussian than for multimode beam ablation. Background emission decreased for plasma induced by multimode beam when using double pulse mode while for Gaussian beam an opposite dependence was observed. Surprisingly, higher peak fluence at sample surface for Gaussian beam didn't provide higher plasma temperature and electron density for double pulse ablation. Analytical capabilities of LIBS method were compared for double pulse plasma induced by Gaussian and multimode beam in terms of precision, sensitivity and linearity of calibration curves. It was observed that Gaussian beam sampling leads to improvement of analysis precision while sensitivity was element dependent.

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.

In this work, we studied a technology of laser-induced coloration of metals by surface oxidation. A method of complete color palette development for enhancement of the technological industrial application is demonstrated for the 1.06 μm fiber laser with nanosecond duration of pulses. It is based on reflectance spectra dependence on laser processing parameters. AISI 304 stainless steel example confirms an applicability of this method. However, the results can be similarly used for other oxidizing metals and alloys under normal conditions. Sample color dependence on the light incidence angle (viewing angle) is also presented. Keywords: Color laser marking, Spectrophotometry, Laser oxidation, Complete color palette, Stainless steel

This paper proposes what we believe to be a novel approach for producing color art miniatures with modern photonic devices and laser technology. We discuss the concept and basic design for a “laser paintbrush” device based on an ytterbium-fiber nanosecond pulsed laser. A functional demonstration of the proposed approach is performed by creating a sample color miniature on a titanium surface. We study the optical properties of the “painted” areas to determine the range of laser parameters suitable for such a device.

We developed a surface design that imitates the osteon structure of human bone tissue to improve the bio-integration of a titanium implants. Two types of subcellular-sized microgrooves were formed on VT6 (analogue 6Al-4V) titanium surface by laser processing: closed and open microgrooves. An in vitro study of the proliferation of human bone marrow mesenchymal stem cells on the formed structures was carried out, osteogenic differentiation was studied.

Ambient-air single-shot ablative femtosecond laser surface processing of an advanced Al-alloy AA5083 was characterized by non-contact broadband ultrasonics, scanning electron microscopy with energy-dispersive x-ray spectroscopy, x-ray diffraction, and Vickers microhardness tests. The characterization indicates that the generated Mbar-level shock waves induce not only a strong structural modification of the processed micron-thick surface layer with sub-GPa-level residual compressive and tensile stresses, raising its microhardness by almost 45%, but also significant depth-dependent chemical modification within the layer.