Analysis of experimental data obtained in study of cryogenic CO laser with glow discharge and cryogenic slab CO laser with RF discharge showed that oxygen concentration in laser mixture is much less than in initial gas mixture. With low oxygen content, ozone plays role of supplier of electrons in cryogenic discharge. Since ionization potential of ozone is somewhat higher than that of oxygen, and ozone quickly condenses on cold walls of cryogenic discharge, conversion of O2 to O3 is accelerated. In addition, in plasma-chemical reactions, ozone regenerates carbon monoxide after dissociation. Acceleration of ozone generation in cryogenic barrier discharge was experimentally demonstrated.
Different frequency conversion processes in the mid-IR were experimentally studied with slab RF discharge CO and CO2 lasers and various nonlinear crystals ZnGeP2, GaSe, BaGa2GeSe6, AgGaSe2 and PbIn6Te10 : second and third harmonic generation of CO laser; sum and difference frequency generation of CO and CO2 lasers. Mid-IR emission on hundreds of narrow spectral lines from 1.7 μm to 19.3 μm was obtained
Super-broadband mid-IR laser systems are under development in the Gas Lasers Lab of the Lebedev Physical Institute. These systems consist of different sorts of molecular gas lasers and various nonlinear crystals converting multi-line emission of those lasers into broadband radiation on sum and difference frequencies. As frequency converters, both main mid-IR nonlinear crystals such as ZnGeP2, GaSe, AgGaSe2 and new ones such as BaGa2GeSe6, PbIn6Te10 are applied. As radiation sources, repetitively-pulsed Q-switched lasers pumped by both longitudinal DC discharge and transverse slab RF discharge emitting microsecond pulses, and also actively mode-locked e-beam sustained discharge lasers emitting nanosecond pulses are applied. It was experimentally demonstrated for the developed laser systems to emit broadband radiation on hundreds spectral lines covering mid-IR range from ~1.7 to ~17 micron due to sum and difference frequency generation including third harmonic generation.
The results of the LMR spectra calculation in the 0-1 band of the NO molecule are presented. For the simulation of the spectra in a strong magnetic field the special numerical model was developed. This model allows one to calculate the dependence of Zeeman splitting of ro-vibrational lines of the NO molecule on the intensity of a strong magnetic field. The analysis of temporal behavior of the absorption coefficients of CO laser radiation on thirteen lines in the variable magnetic field was done.
The results of experimental and theoretical study of the Zeeman splitting of the vibrational-rotational lines in the NO molecule as a function of magnetic field are presented. To record the spectrum the method of laser magnetic resonance (LMR) with using continuous wave frequency-tunable CO laser has been applied. To analyze experimental data of Zeeman splitting, the calculation procedure was developed. This procedure is based on the numerical diagonalization the matrix of the effective molecular Hamiltonian, which includes Zeeman operator corresponding to interaction an external magnetic field with a molecule.
Laser system emitting within IR wavelength range from 2.5 to 16.57 micron is discussed. The hybrid laser system
consists of molecular gas lasers with a frequency conversion in a nonlinear crystal. One gas laser is a carbon monoxide
laser operating in multi-line or single-line mode. Another one is a carbon dioxide laser operating in multi-line mode.
These lasers operate in a Q-switched mode. The laser emission is mixed in various nonlinear crystals producing sum and
difference frequency conversion into above mentioned broadband IR spectral range.
A Master Oscillator - Power Amplifier (MOPA) carbon monoxide laser system emitting nanosecond pulses was
developed on the basis of the wide-aperture pulsed electron-beam-sustained-discharge CO-laser facility. Amplification
parameters including gain and saturation intensity of amplifying media consisted of gas mixtures CO : He or CO : Ar
were measured. The MOPA system emitted a train of nanosecond pulses with peak power up to ~0.1MW on a single
spectral line and up to ~0.4MW with multiline spectrum.
Experimental and modeling results on CO laser frequency conversion are presented. A Q-switched multiline CO laser
with pulse repetition rate 20-150 Hz of sub-microsecond pulses and electron beam sustained discharge frequency-tunable
mode-locked CO laser were used in the experiments on second harmonic generation (SHG) in high-quality ZnGeP2 and
GaSe crystals. Internal SHG efficiency exceeded 12.4 % in 12 mm ZnGeP2 crystal. The SHG in 4 mm GaSe crystal was
observed with internal efficiency of 0.3%. A possibility of difference frequency generation of fundamental and firstovertone
CO laser lines to cover spectral range of ~4.0-5.0 μm is discussed. It is estimated that the difference frequency
generation of neighboring lines of both fundamental and first-overtone bands allows one to obtain oscillation in THz
spectral range within ~200-3000 μm.
Possibility to apply wide range CO-laser for detection of trace gas pollutions in multicomponent gas mixture is studied
both theoretically and experimentally. Parameters of sensitivity and selectivity for multicomponent gas analysis with
CO-laser were calculated.
Results of experimental and theoretical study of singlet delta oxygen (SDO) production in transverse gas flow RF slab
discharge for an electric discharge oxygen-iodine laser are presented. The electric discharge facility operating in both
pulse-periodic and CW mode was manufactured: gas flow duct including multi-path cryogenic heat exchanger, dielectric
slab channel, and slab electrode system incorporated in the channel for RF discharge ignition. Experiments on SDO
production in transverse gas flow RF discharge were carried out. SDO production depending on gas mixture content and
pressure, gas flow velocity, and RF discharge power was experimentally studied. It was shown that SDO yield increased
with gas pressure decrease, gas flow deceleration and helium dilution of oxygen at the same input power. CW RF
discharge was demonstrated to be the most efficient for SDO production as compared to pulse-periodic RF discharge
with the same averaged input power. SDO yield was demonstrated to be not less than 10 percent. The model developed
was further modified to do simulations of CW and pulse periodic RF discharges. A reasonable agreement between
experimental and theoretical data on SDO production in CW and pulse-periodic RF discharges in oxygen is observed.
Experimental and theoretical study of influence of nitrogen oxides NO and NO2 admixtures in oxygen containing gas
mixture excited by pulsed electron-beam sustained discharge on input energy and time behavior of singlet delta oxygen
(SDO) luminescence was carried out. Temperature dependence of the constant of SDO relaxation by unexcited
molecular oxygen was estimated.
Actively mode-locked electron-beam-sustained-discharge CO-laser producing a train of ~5-15 ns (FWHM) spikes
following with repetition rate 10 MHz for both single-line and multiline mode of operation in the mid-IR range of
~5 micron was experimentally studied. Total laser pulse duration was ~0.5 ms for both mode-locked and free running
laser. Specific output energy in multiline CO-laser mode of operation was up to 20 J l-1 Amagat-1 and the laser
efficiency up to 3.5%. The active mode-locking was achieved for single-line CO-laser mode of operation in spectral
range 5.2-5.3 micron. This sort of radiation can be used for pumping an optical parametric amplifier for optical
stochastic cooling in Relativistic Heavy Ion Collider, for laser ablation, and for studying vibrational and rotational
relaxation of CO and NO molecules.
Actively mode-locked electron-beam-sustained-discharge CO-laser producing ~10 ns (FWHM) pulses repetition rate
10 MHz for both single-line and multiline mode of operation was experimentally studied. The total laser pulse duration
was ~0.5 ms for both mode-locked and free running laser conditions. The specific output energy in multiline CO-laser
mode of operation was up to 20 J l-1 Amagat-1 and the laser efficiency up to 3.5%. The active mode-locking was
achieved for single-line CO-laser mode of operation in the spectral range 5.2-5.3 micron. The radiation can be used for
laser ablation, for pumping an optical parametric amplifier in optical stochastic cooling of relativistic heavy ions, and
for studying vibrational and rotational relaxation of NO molecules.
Influence of nitrogen oxides NO and NO2 on specific input energy (SIE) and time behavior of singlet delta oxygen
(SDO) luminescence excited by pulsed e-beam sustained discharge in oxygen was experimentally and theoretically
studied. NO and NO2 addition into oxygen results in small increase and decrease of SIE, respectively, the latter being
connected with large energy of electron affinity to NO2. The addition of 0.1-0.3% nitrogen oxides was experimentally
and theoretically demonstrated to result in notable enhancement of SDO lifetime, which is related to a decrease of
atomic oxygen concentration in afterglow. There was experimentally demonstrated that for getting high SDO
concentration at gas pressure 30-60 Torr for the time interval less than ~0.5 s one needs to add not less than 0.2%
nitrogen oxides into oxygen. Temperature dependence of relaxation constant for SDO quenching by unexcited oxygen
was estimated by using experimental data on time behavior of SDO luminescence.
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.
Temporal behavior of small signal gain in pulsed CO laser amplifier operating with oxygen rich gas mixtures CO:He:O2 and CO:N2:O2 was experimentally studied. The rich content of oxygen in helium mixture (CO:He:O2 =1:4:2) resulted in ~8-fold increase of the maximum gain on low vibrational transitions (10->9) and strong absorption on high ones (21->20). A high efficient pulsed CO laser operating with gas mixture in which oxygen substituted for nitrogen was launched.
Small signal gain temporal behavior in pulsed CO laser amplifier operating with oxygen rich gas mixtures CO:He:O2
and CO:N2:O2 was experimentally studied. The rich content of oxygen in helium mixture (CO:He:O2=1:4:2) resulted in
~8-fold increase of the maximum gain on low vibrational transitions (10-9) and strong absorption on high ones (21-20).
A high efficient pulsed CO laser operating with gas mixture in which oxygen substituted for nitrogen was launched.
The process of laser ablation of fused and crystal silica and natural silicates induced by pulsed CO2 laser irradiation (total pulse duration of 35 μs, laser pulse rise time of 0.1 μs, pulse energy of 10 J) has been studied. By action of focused laser radiation at the surface of samples the appearance of erosion plume at the irradiated surface take place. For study of ablation regimes the frame image of laser induced plume by use of high speed photography method with 2 microsecond expose of each frame have been made. It has been observed the formation of two different type of laser plume during laser pulse action. First type plume represents a long narrow plume with the onset close to start of laser pulse. The maximal length of this plume is about of 20 millimeter. The second type of plume represents a conical plume with the onset, which is late from laser pulse start for a few microsecond. The first type plume expands in to laser beam direction. The second type plume expands normal to the surface. The velocity of laser plume particles by means of measurements of moment transferred into samples during laser pulse action has been measured. It has been obtained, that value of this velocity varies in region of (l÷3)103 m/s in dependence of laser fluency value. The appearance of first time plume have a threshold which equal to 0.30 kJ/cm2 whereas the appearance of second type plume have not a such threshold and may take place at low laser fluency. We believe, that the first type plume connects with the selective ablation of SimOn complexes whereas second type plume connects with the thermal heating caused by dissipation of laser energy in to system of low frequency acoustics phonons.
Radio frequency discharge CO overtone lasing with output power of 50 W was demonstrated with supersonic cooling system. The lasing was observed on 9→7, 10→4 and 11→9 vibrational transitions at around 2.7 μm wavelength. Fundamental band lasing was observed within 4.9 - 5.7 μm spectral range. Output power of 2.1 kW with efficiency of 21% was obtained in fundamental band. Modeling experiments on electron-beam sustained discharge overtone CO laser demonstrated that the time interval needed to populate high vibrational levels by W pumping is considerably more than transit time from the supersonic nozzle to laser resonator axis in the RF facility. Possibilities of supersonic overtone CO laser design improvement, for instance, gas pre-cooling and excitation in supersonic cavity were discussed.
Characteristics of CW CO laser with supersonic gas flow are discussed. Radio frequency discharge CO overtone (V+2→V) lasing with output power 50 W was demonstrated with gas cooling due to supersonic expansion. The overtone lasing was observed on 9→7, 10→8 and 11→9 vibrational transitions within spectral range 2.6-2.7 μm. The laser active medium length was 10 cm. The small signal gain on the overtone transitions was estimated to be 0.1 m-1. Fundamental band (V+1→V) lasing was observed within 4.9 - 5.7 μm spectral range. In fundamental band output power 2.1 kW with efficiency 21% was obtained, with typical small signal gain being about 1 m-1. Modeling experiments on electron-beam sustained discharge facility were carried out at experimental conditions (gas pressure, temperature) corresponding to those of supersonic gas flow. Possibilities of supersonic overtone CO laser design improvement to obtain overtone lasing on highly excited vibrational transitions of CO molecule corresponding to the spectral range ~3-4 micron are discussed.
Last years, CO laser physics has been advanced by researches of CO overtone laser operated on high vibrational levels. An extension of kinetic model to multi-quantum vibration-vibration exchange and development of fully self-consistent model of CO laser are described. The theoretical model developed is verified by comparison with experimental data on overtone CO laser characteristics and laser gain dynamics. Current status of experimental achievements in CO laser
characteristics in both fundamental and overtone bands are reported.
Time behavior of gas temperature in CO containing gas mixture excited in pulsed electron-beam sustained discharge (EBSD) was experimentally studied under different experimental conditions. To study time behavior of gas temperature, the fact that the gas temperature is equivalent to the rotational temperature of gas molecules was used. Rotational distribution of the excited states of CO molecule was reconstructed from measured small-signal gain dynamics on different ro-vibrational transitions. The time behavior of small-signal gain was obtained with probe low-pressure CW CO laser for ten ro-vibrational spectral lines. Gas mixtures CO:He=1 :4 and CO:N2=1:9 typical for a CO laser were used. It was demonstrated that gas temperature grew from 1 10 K (initial temperature) up ~15O K for the first hundred microsecond after EBSD beginning and was staying at this value for a long time (more than 1 ms) for both gas mixtures. EBSD pulse duration was -3Oµs. The method of reconstruction of gas temperature time history was also applied for oxygen gas mixture CO:O2=1:20 at gas pressure 0.04 atm, which was used for obtaining singlet delta oxygen in EBSD. The method can be used for diagnostic of non-equilibrium gas mixtures containing CO molecule.
Singlet delta oxygen (SDO) production in a pulsed e-beam sustained discharge (EBSD) ignited in molecular oxygen with carbon monoxide stabilizing this discharge is theoretically and experimentally studied. Temporal behavior of SDO concentration and yield in the EBSD afterglow is analyzed. Experimentally measured SDO yield for oxygen mixture O2:Ar:CO=1:1:0.05 at total gas pressure 30 Torr comes up to 7% at specific input energy (SIE) of ~3.0 kJ/(1 atm(O2+CO)), whereas its theoretical value riches ~ 17.5%. The efficiency of SDO production is theoretically analyzed as function of the SIE.
Small-signal gain time behavior for cryogenic pulsed e-beam sustained discharge CO laser amplifier on high (V>15) fundamental band vibrational transitions was studied experimentally for different CO containing gas mixtures including ones typical for CO lasers and amplifiers (CO:He and CO:N2), and CO:O2 used for singlet delta oxygen production.
The problem of development of a singlet delta oxygen O2(1Δg) (SDO) generators alternative to chemical one needs application of the accurate methods of measuring the SDO concentration. A chemical SDO generator providing efficient operation of a chemical oxygen-iodine laser (COIL) is proposed to be used as a reference source for absolute calibration of the system measuring the SDO concentration. The principle of the COIL operation results in the threshold and output COIL parameters make it possible to evaluate the SDO yield with a satisfactory accuracy. A convenient sparger chemical SDO generator was applied as a reference source for absolute calibration of detectors of dimole (λ=634nm) and b→X (λ=762 nm) radiations. The values of b-state concentration formed in a longitudinal electric discharge were evaluated. The intracavity laser spectroscopy (ICLS) was absolutely calibrated for measuring the SDO concentration. ICLS method has a very high sensitivity and makes it possible to monitor the absorption corresponding to the O2(1Δg)→O2(1Σg+) (λ = 1.91 μm) transition. The cross-sections of lines of the Q - branch of the vibrational 0-0 band of the a1Δg → b1Σg+ transition of molecular oxygen were measured. The method developed was applied to measure the concentration of singlet oxygen produced in the microwave discharge. He - Ne laser (λ = 633 nm) was used for absolute calibration of a system monitoring the dimole radiation. The rate constant of the process responsible for dimole emission was measured. The value obtained kd=7.34•10-23 cm3/s is in agreement with literature.
Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressure up to 100 Torr were experimentally studied. The pulsed discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of carbon monoxide or hydrogen, the electric stability of the discharge increases, specific input energy (SIE) per molecular component being more than order of magnitude higher and coming up to 6.5 kJ/(l atm) for gas mixture O2:Ar:CO = 1:1:0.1. The results of experiments on spectroscopy of the singlet delta oxygen O2(a1Δg)(SDO) and O2(b1Σg+) states in the EBSD are presented. The calibration of the optical scheme for measuring the SDO absolute concentration and yield using the detection of luminescence of the SDO going from a chemical SDO generator was done. The preliminary measurement of the SDO yield demonstrated that it was ~3% for the SIE of ~1 kJ/(l atm), which is close to the results of theoretical calculations for such a SIE. Theoretical calculations demonstrated that for the SIE of 6.5 kJ/(l atm) the SDO yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature, although a part of the energy loaded into the EBSD goes into the vibrational energy of the molecular admixture, (which was experimentally demonstrated by launching a CO laser operating on an oxygen-rich mixture O2:Ar:CO = 1:1:0.1 and measuring its small-signal gain).
The laser ablation of fused and crystal silica and natural silicates induced by pulsed CO2 laser irradiation (total pulse time of 35 μs, pulse increase time of 0,1 μs, pulse energy of 10 J) has been studied. By action of focused laser radiation at the surface of samples the appearance of erosion plume at the irradiated surface take place. For study of ablation regimes the frame image of laser induced plume by use of high speed photography method with 2 microsecond expose of each frame have been made. It has been observed the formation of two different type of laser plume during laser pulse action. First type plume represents a long narrow plume with the onset close to start of laser pulse. The maximal length of this plume is about of 20 millimeter. The second type of plume represents a conical plume with the onset, which is late from laser pulse start for a few microsecond. The first type plume expands in to laser beam direction. The second type plume expands normal to the surface. The velocity of laser plume particles by means of measurements of moment transferred into samples during laser pulse action has been measured. It has been obtained, that value of this velocity varies in region of 1-3•103 m/s in dependence of laser fluency value. The appearance of first time plume have a threshold which equal to 0,15 kJ/cm2 whereas the appearance of second type plume have not a such threshold and may take place at low laser fluency. We believe, that the first type plume connects with the selective ablation of SimOn complexes whereas second type plume connects with the thermal heating caused by dissipation of laser energy in to system of low frequency acoustics phonons.
Small-signal gain time behavior for a pulsed e-beam sustained discharge CO laser amplifier operating on fundamental band vibrational transitions V → V-1 from 6 → 5 (λ ~ 5.0 μm) up to 32 → 31 (λ~7.5 μm) was studied both experimentally and theoretically at various parameters of active medium. Special attention was paid to the small-signal gain time behavior on high vibrational transitions (V > 15). As was previously shown by us, multi-quantum theoretical model of vibrational exchange has to be applied for a correct description of a CO laser operating on vibrational transitions V → V-1 with V higher than 15 instead of a single-quantum one. To make easier theoretical interpretation of the experimental results, the binary nitrogen free gas mixture CO:He = 1:4 was used in our experiments. Total gas density and initial gas temperature was 0.12 Amagat and ~100 K, respectively. The complete kinetic model of a CO laser taking into account multi-qauntum vibrational exchange was employed for theoretical description of the small-signal gain time behavior. The theoretical results were compared with the experimental data.
Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressures up to 100 Torr was experimentally studied in large excitation volume (~18 liter). The discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of carbon monoxide or hydrogen, the electric stability of the discharge increases, specific input energy per molecular component being higher more than order of magnitude and coming up to 6.5 kJ/(l atm). Theoretical calculations demonstrated that for the experimental conditions the singlet delta oxygen yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature. The results of experiments on spectroscopy of the singlet delta and singlet sigma oxygen states in the EBSD are presented.
Temporal behavior of small signal gain (SSG) for a frequency tunable first-overtone CO laser has been studied both experimentally and theoretically. The laser operates on highly excited vibrational transitions from 20→18 up to 38→36 that correspond to laser wavelength range between ~3 and 4 microns coinciding to atmospheric 'transparency window'. Maximum SSG comes up to 0.4 m-1. It is shown that multiquamtum and asymmetric VV exchange has to be taken into account when analyzing processes of population formation on high vibrational transition.
Laser annealing, laser surface processing and laser lift-off procedure are reviewed as applied to semiconductor nitride- based structures (GaN films and InGaN/GaN optoelectronic device structures grown on sapphire substrates). Data on laser ablation of composite GaN/sapphire material are reviewed with more detailed consideration of the ablation rate under subpicosecond laser pulses and under long-pulse irradiation in the IR range (wavelengths of 5.0-5.8 and 9.6 micrometers ).
Studies of vibration-vibration exchange in CO molecules excited up to vibration quantum numbers v=20 are performed both theoretically and expethnentally. New kinetic model taking into account muhi-quantum VV exchange in temperature range T=100Ö300K is described for the first time. Description of the experimental methodology allowing for studies of effects of relaxation of the vibrational distribution after a sudden disturbance is given. The disturbance of the vibrational distribution is produced by Q-switched short pulse of single line radiation in fundamental band The relaxation is studied by measuiing laser pulse energy of the second pulse initiated by resonator Q-switching produced with variable time delay relative to the first pulse. A set of kinetic rate constants accepted in the model for various gas temperatures, vibration level numbers and number of exehanged vibration quanta from 1 to 4 is presented. Good agreement between experiniental data and results of the advanced theory is the first direct evidence in support of multi-quantum exchange model.
Experiments on laser-rock-fluid interaction have been carried out by using pulsed CO and CO2 lasers which irradiated rocks typical for oil field: sandstone, limestone, shale and granite. Energy fluence and laser intensity on rock surface were up to 1.0 kJ/cm2 and 107W/cm2, respectively. The dependencies of specific energy consumption (i.e. energy per volume needed for rock excavation) on energy fluence, the number of pulses, saturated fluid, rock material and irradiation conditions have been obtained for various rock samples. The dependencies of momentum transferred to the rock on energy fluence for dry rocks and rocks with surface saturated by water or mineral oil have been measured. High-speed photography procedure has been used for analyzing laser plasma plume formation on a rock surface. Infrared spectra of reflectivity and absorption of rocks before and after irradiation have been measured.
Experiments on laser-rock-fluid interactions have been carried out by using pulsed CO and CO2 lasers which irradiated rocks typical for oil field: sandstone, limestone, shale and granite. Energy fluence and laser intensity on rock surface were up to 1.0 kJ/cm2 and 107 W/cm2, respectively. The dependencies of specific energy consumption (i.e. energy per volume needed for rock excavation) on energy fluence, the number of pulses, saturated fluid, rock material and irradiation conditions have been obtained for various rock samples. The dependencies of momentum transferred to the rock on energy fluence for dry rocks and rocks with surface saturated by water or mineral oil have been measured. High-speed photography procedure has been used for analyzing laser plasma plume formation on a rock surface. Infrared spectra of reflectivity and absorption of rocks before and after irradiation have been measured.
Frequency selected Q-switched e-beam controlled-discharge CO- laser has been researched and developed for surface heat treatment of polymeric materials [poly(ethyleneterephthalate) and nylon] having strong absorption bands near wavelength of approximately 6 micrometer. The laser generates pulses (including short ones with duration (tau) 0.1 approximately 1 - 10 microsecond(s) ) having different spectral content within 4.9 - 6.5 micrometer spectral range. Different geometry and methods of irradiation were used to process samples with the laser radiation of different temporal, spectral and energy density characteristics. Different types of microstructure were formed on the surfaces of the samples. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.
Frequency selected Q-switched e-beam controlled-discharge CO-laser has been researched and developed for surface heat treatment of polymeric materials (poly(ethyleneterephthalate) and nylon) having strong absorption bands near wavelength of approximately 6 micrometers . The laser generates pulses (including short ones with duration (tau) 0.1 approximately 1 - 10 microsecond(s) ) having different spectral content within 4.9 - 6.5 micrometers spectral range. Different geometry and methods of irradiation were used to process samples with the laser radiation of different temporal, spectral and energy density characteristics. Different types of microstructure were formed on the surfaces of the sample. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.
Frequency selected Q-switched e-beam controlled-discharge CO-laser has been researched and developed for surface heat treatment of polymeric materials (poly(ethyleneterephthalate) and nylon) having strong absorption bands near wavelength of approximately 6 micrometers . The laser generates pulses (including short ones with duration of (tau) 0.1 approximately 1 - 10 microsecond(s) ) having different spectral content within 4.9 - 6.5 micrometers spectral range. Different geometry and methods of irradiation were used to process samples with the laser radiation of different temporal, spectral and energy density characteristics. Various types of microstructure were formed on the surfaces of the samples. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.
The results are presented of computer modeling jointly with preliminary results of experimental investigations of sequentially Q-switched frequency selected CO laser. Calculations show the essential difference in pulse form and inversion restoration time between the models of single- and multi-quantum vibrational exchange kinetics.
A frequency selected (FS) Q-switched (QS) e-beam controlled- discharge (EBCD) CO-laser has been researched and developed. The laser generates short pulses (tau0.1 approximately equals 1 - 10 microseconds) having different spectral content including single line one within 4.92 - 6.54 micrometer spectral range. An influence of spectral content of CO laser radiation 'locked' or 'blocked' inside a laser resonator on output energy and efficiency of lasing on selected wavelengths has been studied.
An influence of different parameters such as gas pressure, specific input energy, laser mixture content, intensity ratio for probe and co-propagating pumping wave, coherency and geometry, etc., upon characteristics of phase conjugation (PC) signal and PC reflectivity (PCR) at intracavity degenerate four-wave mixing (DFWM) of long pulse carbon-dioxide and carbon lasers radiation in their inverted medium has been studied.
Frequency selected pulsed CO laser was used for surface heat treatment of polymeric materials. Nylon and poly(ethyleneterephthalate) samples having strong absorption bands near wavelength of approximately 6 micrometers were processed by the laser radiation of different temporal, spectral and energy density characteristics by using different geometry and methods of irradiation. Different types of microstructure were formed on the surfaces of the samples. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.
A frequency selected (FS) Q-switched (QS) e-beam controlled- discharge (EBCD) CO-laser has been researched and developed. The laser generates short pulses (tauout approximately 1 - 10 microseconds) having different spectral contents including single line one with 4.95 - 6.50 micrometer spectral range. A special optical scheme has been chosen, which has enabled us to study an influence of spectral contents of CO laser radiation 'locked' or 'blocked' inside a laser resonator on output energy and efficiency of lasing on selected wavelengths. The influence of laser mixture contents, gas pressure and temperature, laser pulse length and spectral width upon the laser characteristics also has been studied. A use of frequency selection and Q-switching decreases the laser efficiency dramatically from approximately 30% for non-selected (NS) free-running (FR) mode of operation down to approximately 0.5% (tauout equals 5 microseconds) for optimal wavelength (lambda approximately 5.3 micrometer) and to 0.1% at the long wave edge of laser spectrum (lambda approximately 6 micrometer). Output energy and laser efficiency strongly depend on the number of short pulses in a train for a single electrical pumping pulse. For instance, eight short pulses lasing (tauout approximately 5 microseconds) has increased the output energy up to approximately 0.5 J (0.6 J/l Amagat) and efficiency up to 0.6%. For some wavelengths the output energy and laser efficiency of FS QS CO laser does not strongly depend on temperature within 100 - 150 K interval. Comparative analysis of NS FR, FS FR, NS QS and FS QS mode of operation of carbon monoxide laser has been done.
A frequency selected (FS) Q-switched (QS) e-beam controlled-discharge (EBCD) CO-laser has been researched and developed. The laser generates short pulses ((tau) out approximately 1 - 10 microsecond(s) ) having different spectral contents including single line one within 4.95 - 6.50 micrometers spectral range. A special optical scheme has been chosen, which has enabled us to study an influence of spectral contents of CO laser radiation `locked' or `blocked' inside a laser resonator on output energy and efficiency of lasing on selected wavelengths. The influence of laser mixture contents, gas pressure and temperature, laser pulse length and spectral width upon the laser characteristics also has been studied. A use of frequency selection and Q-switching decreases the laser efficiency dramatically from approximately 30% for non-selected (NS) free-running (FR) mode of operation down to approximately 0.5% ((tau) out equals 5 microsecond(s) ) for optimal wavelength ((lambda) equals 5.3 micrometers ) and to 0.1% at the long wave edge of laser spectrum ((lambda) approximately 6 micrometers ). Output energy and laser efficiency strongly depend on the number of short pulses in a train for a single electrical pumping pulse. For instance, eight short pulses lasing ((tau) out approximately 5 microsecond(s) ) has increased the output energy up to approximately 0.5 J (0.6 J/l Amagat) and efficiency up to 0.6%. For some wavelengths the output energy and laser efficiency of FS QS CO laser do not strongly depend on temperature within 100 - 150 K interval. Comparative analysis of NS FR, FS FR, NS QS and FS QS mode of operation of carbon monoxide laser has been done.
The results of experiments on four-wave interaction of electron-beam-controlled discharge long pulsed CO2-lasers' (t-20 microsecond(s) ) and CO- lasers' (t approximately 200 microsecond(s) ) radiation inside their active medium are presented. Linearly polarized probe CO2 (CO-) laser beam intersects strong electromagnetic waves counterpropagating through an inverted medium inside the laser resonator. The laser beam reflected from the active medium has been registered both in near-field zone and in far field one. The experiments on recovering of optical images in near-field zone and recovering of angular divergency of laser radiation in far-field zone demonstrated that reflected beam was phase-conjugated one. The reflectivity of phase-conjugated beam was up to 2% for CO2-laser and up to 0.2% for CO- laser. The time-history of phase-conjugation reflectivity and comparison with theoretical results are discussed.
The results of experiments on four-wave interaction of electron-beam-controlled discharge (EBCD) pulsed CO2- and CO- lasers' radiation inside their active medium are presented. Linearly polarized probe CO2 (CO-) laser beam intersects strong electromagnetic waves counterpropagating through an inverted medium inside the laser resonator. The laser beam reflected from the active medium has been registered both in near-field zone and in far field. The experiments on recovering of optical images in near-field zone and recovering of angular divergency of laser radiation in far-field zone demonstrate that the reflected beam was a phase- conjugated one. The reflectivity of the phase-conjugated beam was up to 2% for CO2- laser and up to 0.2% for CO- laser. The time-history of phase-conjugation reflectivity and comparison with theoretical results are discussed.
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