Proceedings Volume 6735

International Conference on Lasers, Applications, and Technologies 2007: High-Power Lasers and Applications

Vladislav Panchenko, Vladimir Golubev, Andrey Ionin, et al.
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Proceedings Volume 6735

International Conference on Lasers, Applications, and Technologies 2007: High-Power Lasers and Applications

Vladislav Panchenko, Vladimir Golubev, Andrey Ionin, et al.
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 14 August 2007
Contents: 8 Sessions, 43 Papers, 0 Presentations
Conference: International Conference on Lasers, Applications, and Technologies '07 2007
Volume Number: 6735

Table of Contents

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Table of Contents

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  • Front Matter: Volume 6735
  • Chemical Lasers
  • Electric Discharge Lasers
  • High-Peak Power Laser Systems
  • Laser Design and Laser Beam Control
  • Applications in Industry
  • Laser-Matter Interaction
  • Post-Deadline Papers
Front Matter: Volume 6735
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Front Matter: Volume 6735
This PDF file contains the front matter associated with SPIE Proceedings Volume 6735, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing. The volume has three sections: High-Power Lasers and Laser Systems; Applications of High-Power Lasers; and Post-Deadline Papers.
Chemical Lasers
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Contribution to development of chemical and discharge oxygen-iodine lasers
Jarmila Kodymová, Otomar Špalek, Vít Jirásek, et al.
A chemical centrifugal spray generator of singlet oxygen, chemical methods of atomic iodine generation, and discharge generation of atomic iodine for chemical and/or discharge oxygen iodine lasers (COIL and/or DOIL) are the topics investigated currently in the Institute of Physics AS in Prague. Some main results of this research are presented on a background of the general COIL technology.
Dissociation of I2 in chemical oxygen-iodine lasers: experiment, modeling, and pre-dissociation by electrical discharge
A. Katz, K. Waichman, Z. Dahan, et al.
The dissociation of I2 molecules at the optical axis of a supersonic chemical oxygen-iodine laser (COIL) was studied via detailed measurements and three dimensional computational fluid dynamics calculations. Comparing the measurements and the calculations enabled critical examination of previously proposed dissociation mechanisms and suggestion of a mechanism consistent with the experimental and theoretical results obtained in a supersonic COIL for the gain, temperature and I2 dissociation fraction at the optical axis. The suggested mechanism combines the recent scheme of Azyazov and Heaven (AIAA J. 44, 1593 (2006)), where I2(A'3Π2u), I2(A3Π1u) and O2(a1&Dgr;g, v) are significant dissociation intermediates, with the "standard" chain branching mechanism of Heidner et al. (J. Phys. Chem. 87, 2348 (1983)), involving I(2P1/2) and I2(X1&Sgr;+g, v). In addition, we examined a new method for enhancement of the gain and power in a COIL by applying DC corona/glow discharge in the transonic section of the secondary flow in the supersonic nozzle, dissociating I2 prior to its mixing with O2(1&Dgr;). The loss of O2(1&Dgr;) consumed for dissociation was thus reduced and the consequent dissociation rate downstream of the discharge increased, resulting in up to 80% power enhancement. The implication of this method for COILs operating beyond the specific conditions reported here is assessed.
Advanced singlet oxygen generator and nozzle bank in traditional COIL technology
Marsel V. Zagidullin, Valery D. Nikolaev, Nikolay A. Khvatov, et al.
A centrifugal bubbling SOG generated gas flow with partial oxygen pressure up to 40 torr at singlet oxygen yield about 60% and residual chlorine less than 10%. At initial BHP temperature 260K and ratio of chlorine molar flow rate to BHP volumetric rate of 1mole/litre the output BHP temperature was 290K and water vapor fraction relative to the oxygen was 15%. An oxygen flux up to 6 mmole/s per 1 cm2 of the bubbler surface has been attained. An ejector nozzle bank generates gain medium flow at Mach number ~2 and temperature lower 200K with small signal gain higher 1%/cm. Ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power 6 kW per 1 litre/s of BHP volumetric rate.
Chemical oxygen-iodine laser with atomic iodine generated via fluorine atoms
Otomar Špalek, Vít Jirásek, Miroslav Čenský, et al.
A chemical method of atomic iodine generation for the chemical oxygen-iodine laser (COIL) was studied. This method is based on fast reaction of gaseous hydrogen iodide with chemically produced fluorine atoms formed by a preceding reaction of molecular fluorine with nitrogen oxide. Iodine atoms were generated in special reactors and injected into the supersonic flow of nitrogen in the COIL cavity. Concentration profiles of atomic iodine both along and perpendicular to the primary gas flow were measured in dependence on flow rates of the reaction gases. Very high concentration of atomic iodine (up to 3.2x1015 cm-3) was measured in the laser cavity with a good yield related to both F2 (up to nearly 100 %) and HI (up to 60%). An important advantage of this method is using of commercially available reactive gases. Some drawback of this method for its application in the COIL is a rather high gas temperature (250 - 400 K).
I2 dissociation pathways in the coil medium
M. V. Zagidullin, V. N. Azyazov, S. Yu. Pichugin
Kinetic model of I2 molecule dissociation in a COIL medium involving vibrationally and electronically excited iodine and oxygen molecules was developed. The current understanding of the problem of the iodine dissociation mechanism in the COIL medium is described.
Possibilities of simultaneous lasing in two different spectral bands on HF and DF molecules in autonomous cw HF/DF laser
A. S. Bashkin, S. N. Petrova, D. V. Polinovsky
Results are given for comparative theoretical analysis of efficiency of various combustor fuels for obtaining high performance parameters of simultaneous lasing in two different spectral bands on HF and DF molecules in the autonomous cw HF/DF laser. The feasibility is shown in making mirrors with the reflectivity of more than 99% simultaneously in these frequency bands.
Numerical simulation of double-band cw HF-HBr chemical laser
B. P. Aleksandrov, A. A. Stepanov
The cw chemical laser generating simultaneously on molecules HF (λ~ 2.7 &mgr;) and HBr (λ~ 4.2 &mgr;) is investigated by means of CFD code based on 2D Navier-Stocks equations. Such laser differs from the conventional cw HF laser by the strong thermal emission. In spite of much weaker gain properties of molecule HBr in comparison with HF it is possible to achieve the HBr laser power ~ 25 W from 1 sm2 nozzle bank surface at lasing zone length ~20 sm. The desirable HF/HBr power ratio can be adjusted by bromine dilution of the secondary fuel.
Comparison of well-known kinetic models by the cw HF and DF chemical lasers numerical simulation
B. P. Aleksandrov, A. A. Stepanov
The comparison of three most popular kinetic packages by the results of the numerical simulations of autonomous cw HF (DF) chemical lasers was carried out The differences in the small signal gains obtained by means of 1976-1977 kinetic package and at 1982 (2002) package reach about of 40...60% for HF laser, and about of 70...80% for DF laser. The comparison of rate constants for separate processes was made.
Electric Discharge Lasers
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Achievement of 30% conversion from O2 to O2(a1Δ) at 50 torr using an integrally cooled, controlled avalanche ionized electric O2(a1Δ) generator
The electric oxygen iodine laser (EOIL) offers a vastly more practical, implementable, and safer alternative to its predecessor, the chemical oxygen iodine laser (COIL), particularly for airborne or other mobile military applications. Despite its promise and after 25 years effort, numerous laboratories around the world have not succeeded in providing the known basic physical requirements needed to electrically convert O2 into O2(a1Δ)with the fractional yields and efficiencies needed to make a practical laser. Hence, as of this date, the world record power generated from an EOIL device is only 5 watts. In this paper, a 30% conversion from O2 into O2(a1Δ) operating at substantial oxygen mass flow rates (0.090 moles O2/sec at 50 torr) and 40% electrical efficiency is reported. The O2(a1Δ) flow stream being produced carries 2400 watts. Gain measurements are currently in progress, to be followed shortly by power extraction. Current conditions imply that initial power extraction could push beyond 1 KW. Efforts to date have failed to generate substantial laser power because critical criteria have not been met. In order to achieve good O2(a1Δ) fractional yield, it is normally mandatory to impart on the order of 100 KJ/mole O2 while efficiently removing the waste heat energy from the generator so that less than a few hundred degrees Kelvin rise occurs due to gas heating. The generator must be excited by an electric field on the order of 10 Td. This is far below glow potential; hence, a fully externally sustained plasma generation technique is required. Ionization is supplied by means of applying short (tens of nanosecond) pulses to the O2(a1Δ) generator at 50,000 PPS, which are on the order of ten times breakdown potential. This enables a quasi-steady adjustable DC current to flow through the generator, being conducted by application of a DC, 10 to 14 Td pump E-field. This field is also independently tunable. The result is that up to 180 KJ/mole O2 gets imparted to the gas by means of the ~6 KW subbreakdown pump field, while another 2700 watts is applied to the controlled avalanche field. The generator consists of 24 each, 1 cm diameter tubes that are submerged in rapidly circulating cold fluorinert. Heat is efficiently removed so that that the gas temperature, initially 273°K, raises only by 125°K, as evidenced by spectrographic analysis of the fine structure of O2(b1Σ) at lower pressure. Since all necessary conditions have been met, a 30% conversion rate of O2 to O2(a1Δ) has been achieved. Fortuitously, neither O atom production nor O2(b1Σ) production is visible in the spectra of the higher pressure, best yield runs. Essentially all other spectral lines are dwarfed in comparison the O2(a1Δ) line. Energy normally partitioned to O2(b1Σ) and apparently O atoms now feeds into O2(a1Δ) directly, enabling electrical efficiency to exceed 40%.
Gas discharge lasers pumped by generators with semiconductor opening switch
Alexei N. Panchenko, Alexei E. Tel'minov
Laser and discharge parameters in mixtures of rare gases with halogens driven by a pre-pulse-sustainer circuit technique are studied. Inductive energy storage with semiconductor opening switch was used for the high-voltage pre-pulse formation. It was shown that the pre-pulse with a high amplitude and short rise-time along with sharp increase of discharge current and uniform UV- and x-ray preionization allow to form long-lived stable discharge in halogen containing gas mixtures. Improvement of both pulse duration and output energy was achieved for XeCl-, XeF-, KrCl- and KrF excimer lasers. Maximal laser output was as high as 1 J at efficiency up to 4%. Increase of the radiation power and laser pulse duration was achieved in N2-NF3 (SF6) and He-F2 (NF3) gas mixtures, as well.
Microwave excited planar CO2-laser
Alexander P. Mineev, Sergey M. Nefedov, Pavel P. Pashinin
In this paper reported are the experimental results of investigations the compact planar MW excited CO2-laser. A breadboard model of the planar CO2-laser excited by a wide-aperture MW discharge of 2x25x250 mm size at a frequency 2.45 GHz was elaborated and constructed. The model includes the following basic components: a primary power supply of a magnetron 2M-130, a microwave waveguide, a planar gas-discharge system, and optical-cavity unit. The optical resonator consisted of two plane mirrors, which were placed 2.5 mm from waveguide. Test experiments were carried out with a repetitive uniform MW discharge with 20 ms pulse duration, 0.4-7.0 kHz repetition frequency at level of the input MW power up to 7 kW per pulse. Average laser output power of 25 W (peak power up 580 W) and operating efficiency of 13% at gas pressure of 30 Torr were obtained without optimization of all laser parameters.
Cryogenic sealed-off slab CO laser excited by repetitively pulsed RF discharge
A. A. Ionin, L. V. Seleznev, A. V. Shelestovich, et al.
First experiments on fundamental band CO lasing in sealed-off cryogenically cooled slab facility with RF discharge excitation were carried out. Repetitively pulsed and CW modes of RF discharge excitation were studied. The laser output characteristics for different slab geometries were compared. Average output power achieved 12 W. Lasing efficiency came up to ~14 %. The output laser spectrum was observed within wavelengths range 5.08-5.34 &mgr;m. Stable lasing was obtained for more than one hour. Preliminary study of single-line lasing was carried out.
High-efficient discharge-pumped ArF (193 nm) excimer laser with a TPI thyratron as a high-voltage switch
Alexander M. Razhev, Andrey A. Zhupikov, Dmitry S. Churkin
The results of using the thyratron of the TPI series (pseudo spark gap) as a high-voltage switch in the excitation system of ArF (193 nm) excimer laser are presented. The excitation system of the LC-inverter type based on TPI 10k/20 thyratron in absence of any non-linear elements was developed. An experimental investigation of the energy and temporal parameters of the pumping and lasing for ArF laser on the He:Ar:F2 mixture with excitation system developed was carried out. The comparative analysis of the ArF laser pumping and radiation parameters in dependence of the high-voltage switch type such as a standard spark gap RU-65, and thyratron TPI 10k/20 was performed. The output radiation energy for a laser with thyratron TPI 10k/20 was obtained to be of 1.4 times higher than that with standard spark gap RU-65 at the same pumping conditions. Such increase the output energy was shown to be achieving owing to higher level of the pumping intensity due to higher voltage on the discharge gap that occurs due to lower energy losses into TPI thyratron in comparison with the RU- 65 spark gap and leads to more efficient energy transfer from storage to discharge circuit. As a result for ArF laser with TPI thyratron in He:Ar:F2 mixture the output radiation energy of 1.0 J with the total efficiency of 1.7% has been achieved. The advantages of using the TPI thyratron in the excitation system of the ArF excimer laser over spark gap are described.
Long-pulse discharge nitrogen lasers
I. N. Konovalov, A. I. Suslov, V. F. Tarasenko, et al.
We report development of long-pulse discharge N2-lasers pumped by inductive energy storage with maximal radiation parameters. The laser output from an active volume with cross-section up to 6×10 cm2 was as high as 110 mJ with peak power of about 6 MW. In mixtures of nitrogen with NF3 laser pulses about 100 ns in duration were obtained. Numerical model of nitrogen laser on mixtures of nitrogen with electronegative gases pumped by transverse discharge is developed. This model allows to simulate laser parameters on transition C3ΠuB3Πg and predict the laser operation in different experimental conditions.
Pulsed CO laser operating on gas mixtures with high oxygen content
Yu. M. Klimachev, A. A. Ionin, A. A. Kotkov, et al.
Temporal behavior of small signal gain (SSG) in pulsed CO laser operating on oxygen rich gas mixtures CO:He:O2=1:4:X and CO:N2:O2=1:9:X was studied experimentally. The rich content of oxygen (X≥2) in these mixtures resulted in significant increase of the maximum gain on low (6≤V≤13) vibrational transitions V+1→V and strong absorption on high ones (V≥18). Both fundamental and first overtone CO lasing on these gas mixtures were studied. The threshold energy input is demonstrated to be diminished at addition of O2 for pulsed EBSD CO-laser operating on either fundamental or overtone transitions, with maximum laser efficiency increasing. It is shown that pulsed EBSD CO-laser can effectively operate on air-containing gas mixtures.
Generation of a high quality short pulse in excimer lasers at use of SBS mirror
In the present paper the results of an experimental research of a qualitative radiation formation with pulse duration of 3.5 and 0.15 nanoseconds in one discharge block of XeCl laser with pump pulse duration of 35 ns at use resonator with SBS mirror are presented.
High-Peak Power Laser Systems
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Development of petawatt laser amplification systems at the Central Laser Facility
O. Chekhlov, E. J. Divall, K. Ertel, et al.
We describe two development projects: Astra-Gemini: a Petawatt class system based Ti: Sapphire amplifiers and a 10 PW upgrade for the Vulcan laser. The design concepts, features of the optical design of amplifiers and compressors are presented. Radial delay compensation techniques used for a 3-x beam expander are discussed.
High power optical sources of femtosecond pulses on the base of hybrid laser systems with wide-aperture gas laser amplifiers
A. A. Ionin, A. V. Konyashchenko, B. M. Koval'chuk, et al.
The multi-stage hybrid laser system producing ultrashort pulses of radiation with peak power ~1014 - 1015 W now under developing at the Lebedev Physical Institute of the Russian Academy of Sciences is discussed. The distinctive feature of the laser system is direct amplification of ultrashort pulses produced by solid state laser system, first going through a prism stretcher with negative dispersion, in gas active medium without using a rather expensive and complicated grating compressor of laser pulses. Two hybrid schemes are being developed now based on the amplification of femtosecond pulses of the third harmonic of Ti:Sapphire laser at the wavelength 248 nm in the active medium of KrF laser amplifier, and on the amplification of the second harmonic of Ti:Sa laser at the wavelength 480 nm in the active medium of photochemical XeF(C-A)laser excited by VUV radiation of an e-beam pumped Xe2 lamp. The final stage of the laser system is supposed to be an e-beam pumped facility with a laser chamber of 60 cm in diameter and 200 cm long in the case of KrF laser, and with another laser chamber of 30-40 cm in diameter put into the former one in the case of XeF(CA) laser. The parameters of such e-beam facility are close to those of previously developed at the Institute of High- Current Electronics: electron energy ~600 keV, specific input power ~ 300-500 kW/cm3, e-beam pulse duration ~ 100- 200 ns. A possibility of using Kr2F as an active medium with saturation energy 0.2 J/cm2 for amplification of ultrashort laser pulses is also under consideration. There was theoretically demonstrated that the energy of a laser pulse at the exit of the final stage of the laser system could come up to ~ 17 J with pulse duration ~50 fs in the case of KrF laser, and ~75 J with pulse duration of 25 fs in the case of XeF laser. Two Ti:Sa laser systems producing ~50 fs pulses with energy ~0.5 mJ at the wavelength 248 nm and ~5 mJ at the wavelength 480 nm have been already developed and are being now installed at the Lebedev Institute. Preliminary experiments on amplification of UV femtosecond pulses were carried out with electric discharge KrF laser amplifier.
Sub-picosecond petawatt class N2O laser system: mid-IR non-linear optics and new possibilities for high-energy physics
V. M. Gordienko, V. T. Platonenko, S. G. Rykovanov, et al.
Progress on developing a petawatt laser source in 10&mgr;m region is described. Analysis of optical pumping N2O containing active media by pulsed multifrequency HF laser has been performed. It is shown that amplification of ultrashort pulses should be carried out in the gain band centered at 930cm-1. Amplification of seed ultrashort (~1ps) pulses in atmospheric and high pressure N2O (up to 5atm) amplifiers pumped by powerful pulsed HF chemical lasers is theoretically studied. It is shown that N2O atmospheric pressure amplifiers can be effectively used for production output energy of 1kJ. We discuss a simple add for subpicosecond N2O- laser system to generate joule-level 200 fs pulses with high temporal quality and an overall conversion efficiency of 80%. Petawatt class N2O laser could be prospective for strong-field physics applications and production of high energy proton beams upon irradiating gas jets.
Formation of short high-power laser radiation pulses in excimer mediums
N. G. Ivanov, Yu. N. Panchenko
Presently an excimer mediums continue are examined as one of variants for formation of powerful and over powerful pulses of laser radiation with duration from units of nanosecond up to tens femtosecond. The researches on such powerful installations as "NIKE" (USA) and << SUPER ASHURA >> (Japan) proceed in this direction. The main advantage of excimer mediums is the opportunity to work in a frequency mode, absence of restriction on the size of active area, high uniformity of a gas working medium, high efficiency (up to 10 %) and wide spectral range of laser radiation (KrF, XeCl ~ 2nm, XeF (C-A), Xe2Cl ~ 50-100 nanometers). Research in area of high quality laser beams formation in excimer mediums and its amplification in high power amplifiers are carried out the long time in Institute of High Current Electronics SB RAS, Tomsk, Russia. The wide aperture XeCl laser system of MELS-4k is used for these investigations. Last time we take part in program on development of high power excimer laser system with a petawatt level of power. This system supposes the formation and amplification high quality laser beams with different pulse duration from units of nanosecond up to tens femtosecond. We research the possibility of laser beams formation in excimer mediums with ps-ns pulse duration having the low noise and divergence near to diffraction limit. In other hand, we are developing the wide aperture XeF(C-A) amplifier with optical pump on base electron accelerator. According to our estimations of the XeF(C-A) amplifier based on the converter of e-beam energy to the Xe2* fluorescence at 172 nm will allow to obtain up to 100 TW peak power in a 30 fs pulse.
Suppression of gain narrowing with a combination of negative and positive CPA
M. P. Kalashnikov, K. Osvay
A laser scheme implementing a combination of negatively- and positively-chirped pulse amplification (NPCPA) is demonstrated. This method of amplification suppresses spectral narrowing typically appearing in chirped pulse amplification (CPA) lasers thus supports pulse spectrum substantially broader than a conventional CPA. With a NPCPA Ti:sapphire laser we have achieved laser pulses of 50 nm spectral width and 150 mJ energy without any additional spectral correction. The scheme appears as an easy and reliable solution to preserve spectral bandwidth in Ti:Sapphire lasers, especially at Petawatt and higher power levels.
Design and construction of a PW ultrashort laser facility with ns, ps, and fs outputting pulses
Qihua Zhu, Xiaojun Huang, Xiao Wang, et al.
A petawatt laser facility with three beams for fast ignition research and strong-field physics applications has been designed and is being constructed. The first beam (referred as SILEX-I) is a Ti:sapphire femto-second laser which pulse width is 30 fs, and till now, output power has reached to 330 TW. The other two beams are Nd3+:glass lasers which output energy are larger than 1kJ and pulse width are about 1ps and 1ns respectively. By using the technology of OPA pumped by 800nm femtosecond laser and seeded by super-continuum white light (SWL), the three beams are synchronized with each other without jitter time. Tiled multilayer dielectric coating gratings are used for the compressor of the PW beam.
Laser Design and Laser Beam Control
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Laser systems for pulsed volumetric laser beams generation
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.
Short-pulse disk laser
Yu. Chivel, I. Niconchuk, D. Zatiagin
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.
High-energy diffractive variable attenuator
A. G. Poleshchuk, A. I. Malyshev
New type of optical attenuator on the base of circular phase grating to control of high power laser radiation is developed. Theory, design and experimental investigation of polarization independent diffractive attenuators are presented.
Optical experimental fiber for transmission of high-power laser radiation
New optical experimental fiber with plating of surface allows to increase a range of using an optical fiber and raise field- performance characteristics of the communication links. The optical Bragg fiber with a metallization of a surface is designed. The Bragg fiber is further development multicover fiber. Special refraction index sharing allows to increase the numerical aperture and the transmitted radiation power. Last researches will use the fractal approach in analysis of a radiative transfer in photon crystals.
Applications in Industry
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High-power laser sources for industry and their applications
Despite the invention and availability of a wide variety of laser sources, only very few types have made their way into the industrial use, which very often requires reliable three shift running, high uptime and low running costs. Over a long time the CO2 gas laser has dominated the high power material processing area and still holds with 41.1 % the biggest market share in that field. The most modern, most reliable and most cost efficient type of CO2 laser is the diffusion cooled slab configuration, which provides almost diffraction limited beam quality and is nowadays available in a power range up to 8 kW. The advantage of solid state lasers is that their radiation can be guided through optical fibers, but they suffered from high cost and low efficiency. The appearance of diode lasers as a very efficient and reliable pumping source, however, has boosted solid state laser technology. Not only the beam quality and efficiency of the classical rod design could be improved by replacing broadband lamps by monochromatic diode lasers but furthermore, because of the high brilliance of the diode lasers, new concepts as the thin disc and the fiber laser could be realized. Especially the higher efficiency, reducing the running cost in conjunction with improved beam quality makes the solid state lasers the tool of the future, whenever 3D applications are under consideration.
Dieless wire drawing with lasers
G. Liedl, D. Schuöcker
Thin wires are produced by drawing through nozzle-like tools, so called dies, that suffer from strong wear due to friction. In order to avoid the latter disadvantage the dies can be replaced by a laser beam heating the wire to such extend that the yield strength becomes smaller than the tensile strength and thus the wire is elongated and consequently constricted. To avoid rupture, the wire is cooled down again after the desired reduction of the diameter is reached. A further important advantage of this new process is that only one drawing step with a laser can substitute a large number of mechanical drawing actions, thus making the process much more efficient. Theoretical considerations and experimental investigations prove the feasibility of the latter new laser process and are subject to a description in the actual paper.
Optimization of the quality of laser cutting and power consumption
Ch. Sipavichius, A. Amulevichius, K. Mazheika
Using the Mössbauer spectroscopy and X-ray diffraction methods the chemical composition and the dimensions of particles of erosion products were determined when the distances from the nozzle to the cutting slot were changed. In the addition, the influence of the laser beam power and the parameters of gas flow on their sizes and chemical composition was studied. It has been determined that the chemical changes in erosion products are related to the quality of the cutting slot.
Development of resonators for high-power CO2 lasers
A. M. Orishich, V. B. Shulyat'ev, G. N. Grachev, et al.
A brief review is made for the schemes of optical resonators for the generation of a high-quality beam in high-power CO2 lasers. The main results of the self-filtering resonator application in the industrial laser are presented. The self-filtering resonator is compared to the stable resonator by the output beam characteristics, aberration sensitivity, and laser cut characteristics by the example of steel cutting.
Pulse laser welding of aluminum alloy by combined radiation
Yevgeny A. Chaschin, Igor V. Shilov, Sergey A. Solokhin, et al.
The formation features of welded connections of aluminum alloys by combined laser radiation are considered. The mechanism of a molten pool formation is investigated by numerical modeling and experimentally. The attainment criteria of qualitative butt-welded connection are determined.
Application of Mössbauer spectroscopy in the studies of oxidation of steel
A. Amulevichius, K. Mazheika, Ch. Sipavichius, et al.
Oxides are widely used in the industry and their generation methods have a practical value. Results of the study have shown that for similar laser processing, but for different oxidation conditions, the amounts of oxides can differ from 10 to 80%.
Mechanism of plasma generation under focused beam effect on metallic surface in laser welding
V. S. Golubev, M. G. Galushkin, R. V. Grishaev, et al.
Numerical modeling of the process of thermal ionization associated with the interaction of laser radiation and metal target was performed and the temperature dynamics and the plasma absorptance were obtained. Threshold values of temperature for the appearance of the thermal instability and near-surface optical plasma generation have been derived. The processes in near-surface laser induced plasma in specific conditions of laser welding are under consideration.
Laser-Matter Interaction
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Pulsed plasma thruster based on solid-state lasers
A. N. Chumakov, N. A. Bosak, A. M. Petrenko, et al.
Problems of laser-plasma thruster creation for space applications are analyzed. Results of laboratory researches concerning the choice of solid-state laser, operating mode and target material are considered. Characteristics of micro-thruster with diode pumping are discussed
Deflection of sub-100-fs electrons by femtosecond light
S. A. Aseyev, B. N. Mironov, S. V. Chekalin
Our experimental activity in the field of femtosecond electron optics is described. The final purpose is to generate and characterize a sub-100-fs femtosecond electron beam.
High-power and ultrashort laser pulse ablation of metals: threshold characteristics
I. N. Zavestovskaya, O. A. Glazov, N. A. Menkova
The results of theoretical studies are reported for threshold characteristics of a metal ablation by ultrashort laser pulses. Two possible mechanisms of the laser ablation at laser fluence F≥Fth are considered: thermal mechanism of ablation connected with a kinetics of a metal-vacuum surface evaporation and mechanism of ablation connected with a hydrodynamics of a dense matter. The analysis has been made within the framework of a two-temperature model of metals for two region of laser pulse duration-femtosecond and picosecond, and the extended of a two-temperature model of the metal. Analytical expressions for the ablation-threshold fluency Fth as well as the threshold values of the lattice time temperature Tth(Fth) are obtained.
Laser ablation in liquids: an efficient sample preparation technique in ICP elemental analysis of art materials
N. M. Kozhukh, E. V. Muravitskaya, V. A. Rosantsev, et al.
Laser ablation in liquid media is proposed as a new sample preparation technique in elemental composition analysis of art pigments using inductively coupled plasma optical emission spectroscopy (ICP-OES). Solid samples are transformed to colloidal solutions of nanosized analyte particles. This makes the technique compatible with convevtional solutionbased standardization. The dissociation of particles in solution is improved, which increases the accuracy of quantitative ICP measurements.
Time-resolved measurements of laser plasmas interaction during breakdown in normal atmosphere by various wavelengths
Alexey A. Il'in, Alexey V. Bulanov, Sergey S. Golik
Time-resolved spatial and spectral characteristics of laser plasmas interaction in normal atmosphere are presented. Plasma experiments were performed by using 532 nm (4 ns, 180 mJ) and 1064 nm (5 ns, 360 mJ) pulses from Brilliant B Nd:YAG laser. Laser beams were focused in the opposite directions by lenses with focal distances of 15 mm. Firstly laser breakdown of air by 532 and 1064 nm laser radiation was investigated. Molecular bands, absorption line of atomic oxygen O 777 nm and dip of continuum intensity are recorded at initial instants of laser plasma formation. Mechanisms of plasma expansion are investigated. Relationship of molecular bands, absorption line of atomic oxygen, plasma's UV radiation and fast wave of ionization is discussed. Molecular bands, continuum and line temporal dynamics was investigated during laser plasmas interaction. Three zones of interaction and enhancement of line/continuum ratio is registered. Influence of KrF laser radiation (248 nm, 25 ns, 600 mJ) on parameters of breakdown induced by 532 nm laser radiation is discussed.
Post-Deadline Papers
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Surface-enhanced Raman scattering substrate and microfluidic waveguide fabricated by fs laser microprocessing
Zenghui Zhou, Haiyi Sun, Ya Cheng, et al.
We report the fabrication of novel surface-enhanced Raman scattering (SERS) substrate and microfluidic optical waveguide using fs laser direct writing, which are crucial elements on biophotonic biochips.
LANTCET: laser nanotechnology for screening and treating tumors ex vivo and in vivo
Dmitri O. Lapotko, Ekaterina Y. Lukianova-Hleb, Sergei A. Zhdanok, et al.
LANTCET (laser-activated nano-thermolysis as cell elimination technology) was developed for selective detection and destruction of individual tumor cells through generation of photothermal bubbles around clusters of light absorbing gold nanoparticles (nanorods and nanoshells) that are selectively formed in target tumor cells. We have applied bare nanoparticles and their conjugates with cell-specific vectors such as monoclonal antibodies CD33 (specific for Acute Myeloid Leukemia) and C225 (specific for carcinoma cells that express epidermal growth factor -EGF). Clusters were formed by using vector-receptor interactions with further clusterization of nanoparticles due to endocytosis. Formation of clusters was verified directly with optical resonance scattering microscopy and microspectroscopy. LANTCET method was tested in vitro for living cell samples with: (1) model myeloid K562 cells (CD33 positive), (2) primary human bone marrow CD33-positive blast cells from patients with the diagnosis of acute myeloid leukemia, (3) monolayers of living EGF-positive carcinoma cells (Hep-2C), (4) human lymphocytes and red blood cells as normal cells. The LANTCET method was also tested in vivo using rats with experimental polymorphic sarcoma. Photothermal bubbles were generated and detected in vitro with a photothermal microscope equipped with a tunable Ti-Sa pulsed laser. We have found that cluster formation caused an almost 100-fold decrease in the bubble generation threshold of laser pulse fluence in tumor cells compared to the bubble generation threshold for normal cells. The animal tumor that was treated with a single laser pulse showed a necrotic area of diameter close to the pump laser beam diameter and a depth of 1-2 mm. Cell level selectivity of tumor damage with single laser pulse was demonstrated. Combining lightscattering imaging with bubble imaging, we introduced a new image-guided mode of the LANTCET operation for screening and treatment of tumors ex vivo and in vivo.
Influence of laser beam focusing on LIBS efficiency at the elemental analysis of metals
Efficiency of the Laser-Induced Breakdown Spectroscopy (LIBS) has been studied as applied to the development of a technique for elemental microanalysis of solid samples, when a rather low consumption of the sample material is demanded allowing the technique to be practically non-destructive and applicable, e.g., at art, archaeological, forensic and similar investigations of unique objects. Higher intensity of the laser-induced emission spectra at lower sample erosion result in the increased efficiency of the LIBS analysis. The efficiency depends on many factors and in particular on thermal properties of the sample material and on its excitation conditions. Here, an influence of the laser beam focusing has been studied for samples of Al and Pb alloys having different thermal properties.
Optical, structural, and lasing properties of a composite material nanoporous glass filled with an organic dye-activated polymer
S. S. Anufrik, M. I. Ihnatouski, M. F. Koldunov, et al.
Structural and optical characteristics of polymer-filled nanoporous glass (PFNPG) composite was studied with holographic interferometry and atomic-force microscopy methods. A high homogeneity of the bulk PFNPG samples and their surfaces has been found. Light scattering in the samples was investigated. Rather low scattering losses have been observed in spite of heterogeneous structure of the composite. This result is discussed on a base of the Rayleigh scattering model. Lasing properties including a pump-to-laser conversion efficiency and a life time due to photodestruction of PFNPG samples activated with pyrromethene dyes are reported.