Femtosecond–pulse laser micromachining is based on a laser ablation phenomenon, i.e. total evaporation of material from the target surface during laser irradiation. It is the most precise method of material removal. Moreover it does not... more
Femtosecond–pulse laser micromachining is based on a laser ablation phenomenon, i.e. total evaporation of material from the target surface during laser irradiation. It is the most precise method of material removal. Moreover it does not require any post processing. Removal of the material occurs only in the laser focus, since the lack of thermal interaction, neither heat affected zone (HAZ) nor debris ocur. Research results have shown that shortening the duration of the laser pulse significantly reduces HAZ, which translates into the high quality of the machined structures. It is the main argument for the use of femtosecond-pulse lasers in the precise micromachining. In this paper, a femtosecond laser system consisting of a solid-state oscillator and the ytterbium-doped pulse fiber amplifier are presented. Average beam power at 343 nm with mode-locking is 4W @25A and pulse length at the oscillator output is 500 fs. Laser micro and nano-machining has found application in different fields. It’s primary use is industrial micromachining of metals, ceramics, polymers, glass, biological material for medical use in eye surgery, and photovoltaic cells.
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We studied the nonlinear properties of some of the most promising nonlinear media for microelectronic applications - AlN and GaN. The nonlinear refractive index n2 and the multiphoton absorption ß of the media are measured by femtosecond... more
We studied the nonlinear properties of some of the most promising nonlinear media for microelectronic applications - AlN and GaN. The nonlinear refractive index n2 and the multiphoton absorption ß of the media are measured by femtosecond z-scan method with virtual aperture.
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An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely... more
An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely... more
An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract In this study, synthesis and characterization of novel quaternary tellurite glass system TeO 2 –Bi 2 O 3 –GeO 2 –Li 2 O is presented. The compositions include TeO 2 and GeO 2 as glass formers while different proportion of Bi 2 O... more
Abstract In this study, synthesis and characterization of novel quaternary tellurite glass system TeO 2 –Bi 2 O 3 –GeO 2 –Li 2 O is presented. The compositions include TeO 2 and GeO 2 as glass formers while different proportion of Bi 2 O 3 and Li 2 O act as network modifiers. Differential thermal analysis, X-ray diffraction, scanning electron microscopy energy dispersive X-ray spectroscopy, laser ablation inductively coupled plasma mass spectrometry, UV–Vis and Raman spectroscopy are applied to study the structural, thermal and optical properties of the studied glasses. Obtained glasses possess a relatively low glass transition temperature (around 300 °C) if compared to other tellurite glasses, show good thermal transparency in the visible and near infra-red (from 2.4 to 0.4 μm) and can double the frequency of laser light from its original wavelength of 1064 nm to its second-harmonic at 532 nm (i.e. second harmonic generation).
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Although the low-level laser therapy (LLLT) is accepted in the clinical practice, its efficiency is still questionable because of the unclear mechanisms of LLLT action. This work presents the results of LLLT applied to volunteers who need... more
Although the low-level laser therapy (LLLT) is accepted in the clinical practice, its efficiency is still questionable because of the unclear mechanisms of LLLT action. This work presents the results of LLLT applied to volunteers who need recovery from trauma or suffer from rheumatic diseases, inflammatory disorders, etc. The control group we used for comparison consisted of patients being treated
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This work aims at evaluating the possibility of introducing state-of-the-art commercial femtosecond laser system in restorative dentistry by maintaining well-known benefits of lasers for caries removal, but also in overcoming... more
This work aims at evaluating the possibility of introducing state-of-the-art commercial femtosecond laser system in restorative dentistry by maintaining well-known benefits of lasers for caries removal, but also in overcoming disadvantages such as thermal damage of irradiated substrate. Femtosecond ablation of dental hard tissue is investigated by changing the irradiation parameters (pulsed laser energy, scanning speed and pulse repetition rate), assessed for enamel and dentin. The femtosecond laser system used in this work may be suitable for cavity preparation in dentin and enamel, due to the expected effective ablation and low temperature increase when using ultra short laser pulses. If adequate laser parameters are selected, this system seems to be promising for promoting a laser-assisted, minimally invasive approach in restorative dentistry.
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Laser oscil(•ation on near-infrared cadmium ion transitions was ob- tained in a transverse radio- frequency excited He-Cd discharge. Lasing on two of them: 853.0 nm and 887.8 nm was reported for the first time as iaser oscil- lation... more
Laser oscil(•ation on near-infrared cadmium ion transitions was ob- tained in a transverse radio- frequency excited He-Cd discharge. Lasing on two of them: 853.0 nm and 887.8 nm was reported for the first time as iaser oscil- lation excited by a radio-frequency discharge, T)1e optimum conditions at cw and pulsed mode of operation were determlned yielding a maximum small signal gain coeffilcient of 24 o/o/m for the 806 nm laser. The shnilarity between radio-frequency excited and hollow cathode discharges was proved by the infrared Cd+ Iines behaviour on discharge conditions.
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ABSTRACT In this study stainless steel, silicon and silica glass are used as representatives of metal, semiconductor and isolator with the purpose to create an experimental model for studying the formation of minerals like hydroxyapatite... more
ABSTRACT In this study stainless steel, silicon and silica glass are used as representatives of metal, semiconductor and isolator with the purpose to create an experimental model for studying the formation of minerals like hydroxyapatite (HA, the bone and teeth mineral part) from aqueous solutions. The samples are Na+ implanted and consequently subjected to thermal treatment in air at 873 K. Implantation with Na+ is known to lead to formation of hydroxylated surface, i.e. formation of metal- or Si-OH- groups upon immersion in a liquid, simulating the human blood plasma (simulated body fluid, SBF). The negatively charged hydroxylated surfaces induce HA formation in SBF. The samples are immersed in SBF, irradiated through the solution with a scanning laser beam (CuBr pulsed laser equipped with a scanning system) and subsequently soaked in the solution at 37°C for a shorter time, comparing to the traditional methods for HA growing. The grown HA layers are investigated by Fourier Transform Infrared (FTIR) and Raman Spectroscopies, X-ray Diffraction (XRD), Light Microscopy (LM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) Spectroscopy to evaluate the effect of the surface modification by the thermal treatment following the ion implantation, as well as the effect of the laser irradiation on the process of HA formation.
Research Interests: Engineering, Materials Science, Hydroxyapatite, Raman Spectroscopy, Scanning Electron Microscopy, and 15 moreSilicon, Surface modification, Silica, Stainless Steel, Ion Implantation, Scanning Electron Microscope, Fourier transform infrared spectroscopy, Irradiation, Ion Beam, Light microscopy, Aqueous Solution, Simulated Body Fluid, Blood Plasma, Experimental Model, and Fourier transform infrared
Abstract Possibilities for efficient dye jet laser pumping by CuBr vapor laser are investigated. 8×10 -3 M/1 solution of R590 dye in ethylene glycol is found most suitable for CuBr laser radiation frequency conversion. After experimenting... more
Abstract Possibilities for efficient dye jet laser pumping by CuBr vapor laser are investigated. 8×10 -3 M/1 solution of R590 dye in ethylene glycol is found most suitable for CuBr laser radiation frequency conversion. After experimenting with different dye laser cavity configuration 63% conversion efficiency and tunability in a broad spectral range are achieved.
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After oxygen, silicon is the second most abundant element in the environment and is present as an impurity in most materials. The widespread occurrence of siliceous biominerals as structural elements in lower plants and animals suggests... more
After oxygen, silicon is the second most abundant element in the environment and is present as an impurity in most materials. The widespread occurrence of siliceous biominerals as structural elements in lower plants and animals suggests that Si plays a role in the production and maintenance of connective tissue in higher organisms. It has been shown that the presence of Si is necessary in bones, cartilage and in the formation of connective tissue, as well as in some important metabolic processes. In this work, polycrystalline silicon layers are tested in terms of bioactivity, i.e., their ability to induce hydroxyapatite formation from simulated body fluid. Hydroxyapatite is a biologically compatible material with chemical similarity to the inorganic part of bones and teeth. Polycrystalline silicon layers are obtained by aluminum induced crystallization of Al and amorphous Si thin films deposited sequentially on glass substrates by radio-frequency magnetron sputtering and subsequentl...
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ABSTRACT The laser characteristics of a gold ion laser oscillating on the 282.2-, 284.7-, 289.3-, and 291.8-nm lines are reported. The laser is excited in a longitudinal nanosecond pulsed discharge. Quasi-cw laser generation of 270-mW... more
ABSTRACT The laser characteristics of a gold ion laser oscillating on the 282.2-, 284.7-, 289.3-, and 291.8-nm lines are reported. The laser is excited in a longitudinal nanosecond pulsed discharge. Quasi-cw laser generation of 270-mW average output power and 33%/m small-signal gain are obtained for the strongest line of 282.2 nm. This average output power corresponds to a peak pulsed power of 3.9 W. The reported laser promises various prospects for scientific and technological applications
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Experimental studies of nonlinear frequency conversion of CuBr vapour laser (CBVL) radiation by a beta -BaB2O4 (BBO) crystal are conducted and the results compared to similar ones for a copper vapour laser (CVL). The optimum operating... more
Experimental studies of nonlinear frequency conversion of CuBr vapour laser (CBVL) radiation by a beta -BaB2O4 (BBO) crystal are conducted and the results compared to similar ones for a copper vapour laser (CVL). The optimum operating regime for conversion is determined and the crystal destruction threshold for the authors' operating conditions is found to be 0.5 GW cm-2 for pulses of length 45-50 ns. The nonlinear conversion efficiency of the BBO crystal for frequency doubling of the CBVL radiation is close to that for the CVL radiation. The conversion efficiency for frequency summing is poor compared to that for the CVL-an explanation is offered.
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ABSTRACT We report a novel cooling technique for solid-state laser, which provides opportunity for liquid nitrogen temperature. The cooling holder does not have any windows on the laser beam path in order to avoid dispersion-related... more
ABSTRACT We report a novel cooling technique for solid-state laser, which provides opportunity for liquid nitrogen temperature. The cooling holder does not have any windows on the laser beam path in order to avoid dispersion-related effects in femtosecond lasers. Cw laser oscillation of 4 %Yb3+-doped Y2O3 ceramics at 120 K temperature and 450 mW output power at 1030 nm, was obtained.
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ABSTRACT We fabricated highly transparent Yb3+-doped rare-earth sesquioxide ceramics for solid-state lasers and demonstrated the ceramic lasers. The spectroscopic properties were measured for the low temperature laser operation.
ABSTRACT In this paper the use of stainless steel, silicon and silica glass substrates for the growth of hydroxyapatite (HA, widely used as artificial bone material), induced by a laser-liquid-solid-interaction is reported. The method... more
ABSTRACT In this paper the use of stainless steel, silicon and silica glass substrates for the growth of hydroxyapatite (HA, widely used as artificial bone material), induced by a laser-liquid-solid-interaction is reported. The method allows growing of HA layer by using the interaction between a laser beam and a liquid precursor solution, as well as laser irradiation of the substrate during the laser-liquid interaction. The scanned laser beam (pulsed CuBr laser) is directed at the solid substrate, which is immersed in the solution, which resembles the ion composition and concentrations of the human blood plasma (simulated body fluid, SBF). The set-up includes an open deposition system, which allows the introduction of the laser beam led by a scanning system. It is shown that the proposed method enhances the HA formation, in comparison with the traditional methods of prolonged soaking in SBF. The HA layers grown in this manner are investigated by Light Microscopy (LM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) Spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and Raman Spectroscopy.
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ABSTRACT Hydroxyapatite (HA) is present in the human body as a mineral constituent of the bones and teeth, as well as a major or minor component of kidney stones. HA deposited on different solid substrates can find applications including... more
ABSTRACT Hydroxyapatite (HA) is present in the human body as a mineral constituent of the bones and teeth, as well as a major or minor component of kidney stones. HA deposited on different solid substrates can find applications including biomaterials and biosensors. This work deals with the kinetics of the HA growth by applying a novel method of laser-liquid-solid-interaction (LLSI) process on three types of materials (stainless stell, silicon and silica glass). The method allows interaction between a pulsed laser and a substrate immersed in a solution (simulated body fluid, SBF). By a scanning system, a design of seven squares at a distance of 200 mum was created at the end of each sample. In this way the center of the substrate (about 6x6 mm) was no irradiated. Following the LLSI process, the samples were left in the irradiated SBF for various intervals of time. Light microscopy (LM) showed surfaces seede with randomly distributed transparent and white particles. The surface seeding increased with the immersion time and was dependent on the substrate type. Fourier transform infrared (FTIR) spectrsocopy showed that in the first stage of soaking (up to 6 h) the observed white particles were calcium phosphate containing. Energy dispersive X-ray (EDX) spectrsocopy revealed that the transparent particles were NaCl. In the next stage (after 12 h) vibrational modes typical for HA were clearly observed. Detailed observation with scanning electron microscopy (SEM) after 12 h showed morphology of sphere-like aggregates, grouped in a porous network. Raman spectroscopy, X-ray diffraction (XRD) and EDX confirmed that after 12 h the grown layer was HA. It was found that in comparison to the traditionally empoyed prolonged soaking in SBF, the applied LLSI process yielded a synergistic effect due to the simultaneous use of the solid substrate, the aqueous solution and the laser energy.
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ABSTRACT We have been succeeding in fabrication of highly transparent ceramics and developing new solid-state lasers, ceramic lasers. Femtosceond ceramic lasers and highly efficient cw ceramic lasers were demonstrated with Yb-doped... more
ABSTRACT We have been succeeding in fabrication of highly transparent ceramics and developing new solid-state lasers, ceramic lasers. Femtosceond ceramic lasers and highly efficient cw ceramic lasers were demonstrated with Yb-doped ceramics.
A dye jet amplifier of the 578.2 nm line pumped by the 511.6 nm line of a CuBr vapor laser is investigated. The CuBr vapor laser works at a pulse repetition frequency of 16.6 kHz which has led us to use a jet for the first time. The... more
A dye jet amplifier of the 578.2 nm line pumped by the 511.6 nm line of a CuBr vapor laser is investigated. The CuBr vapor laser works at a pulse repetition frequency of 16.6 kHz which has led us to use a jet for the first time. The effects of the temporal characteristics of the pumping, injecting, and amplifier output pulses are examined. A conversion efficiency of 63%, and an amplification coefficient of 1.75 are reported for the system.
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ABSTRACT A jet nozzle construction is presented which is characterized by highest jet quality and simple design. The jet produced when using the nozzle in conjunction with a circular system of original construction is analysed for... more
ABSTRACT A jet nozzle construction is presented which is characterized by highest jet quality and simple design. The jet produced when using the nozzle in conjunction with a circular system of original construction is analysed for quality. An interferometric method for jet thickness measurement is outlined and used to measure the thickness of the jet. This method proves to be very useful in measuring the thickness of jets formed by other techniques (such as the one described by Bedard et al.). Some performance parameters of a dye jet laser pumped by a quasi-CW CuBr laser are given.