Development of a Chemical Oxygen-Iodine Laser (COIL) with alternative ways of atomic iodine generation is aimed at power increase and simplified laser operation. Advantages of chemical generation of atomic iodine using gaseous reactants directly in the laser medium are confronted with disadvantages of using molecular iodine as a source of atomic iodine in conventional COIL devices. Some recent results on COIL operation with chemically generated atomic iodine supported with computational modeling are presented.

The historical ejector-like chemical oxygen iodine laser (COIL) contribution at the Lebedev Physical Institute, Samara Branch is briefly presented. Two possible schemes of such COIL which provide the high exhaust pressure are considered. The high-pressure hot driver nitrogen is carrier of iodine vapor in the first scheme. In the second version the additional nozzles with the low-pressure secondary nitrogen are employed for injection iodine vapor but the pure high-pressure driver nitrogen has the room temperature. The last COIL version was investigated in Lebedev Physical Institute in more detail and results of these investigations are presented. This ejector nozzle bank generates gain medium with high Mach number, low temperature and high gain. A high chemical efficiency up to 25% and the potential pressure recovery up to 90 torr have been achieved simultaneously.

Pulsed mode makes COIL possible to produce pulses which power can significantly exceed that of CW COIL mode at the same flowrate of chemicals. Such a mode can find application in material treatment, in drilling for oil wells, as an optical locator, in laser frequency conversion via non-linear processes, in laser propulsion, etc. The method of volume generation of iodine atoms was shown to be the most effective one in generation of high power pulses. The base of method is substitution of molecular iodine in operation mixture for iodide which is stable in the mixture with singlet oxygen, and subsequent forced dissociation of iodide. In this approach the advantage of direct I-atom injection in laser active medium is demonstrated. The comparison of experimental results obtained with different sources used for iodide dissociation shows the electric discharge provides significantly higher electrical laser efficiency in comparison with photolysis initiation. At the same time, the specific energy of the electric discharge initiated COIL is at disadvantage in relation with that obtained with photolysis initiation. This fact is a result of active medium temperature increase due to insufficient initiation selectivity of electric discharge. Both longitudinal and transverse electric discharges were investigated as possible sources for laser initiation. The transverse discharge is more promising for increased operation pressure of active medium. The operation pressure is limited by dark reaction of iodide with singlet delta oxygen. The repetitively pulsed operation with repetition rate of up to 75 Hz of pulsed COIL is demonstrated.

The paper considers the physical principles of developing the fullerene-oxygen-iodine laser (FOIL) with optical (sunlight in particular) pumping. Kinetic scheme of such a laser is considered. It is shown that the utmost efficiency of FOIL may exceed 40% of the energy, absorbed by fullerenes. Presented are the experimental results of singlet oxygen generation in liquid media (solutions and suspensions) and in solid-state structures, containing either fullerenes or fullerene-like nanoparticles (FNP). In experiment was shown the possibility of the singlet oxygen transfer to the gaseous phase by means of organizing of the solution (suspension) the boiling as well as of the gasodynamic wave of desorption from the solid-state structures, containing fullerenes or FNP. We present the preliminary experimental results of pulsed generation in optically pumped FOIL with the use of primary photodissociation of iodide for preparation of the atomic iodine in the generation zone. In the experiments on FOIL generation was implemented the principle of spectral separation of optical pumping.

11 kW of COIL power are successfully transmitted through a 20 meter long modified commercial fiber system with optical losses below 10%. The transmission ratio is derived from simultaneous measurement of the laser output power behind the total reflector and the transmitted laser power behind the complete optical fiber system. The fiber delivery system is used to demonstrate cutting of various materials pertinent to dismantling & decommissioning of nuclear installations. Nitrogen and oxygen gas assisted cuts are performed for metal and nonmetal samples, which are made of steel, aluminum, concrete and graphite. The cutting results are validated with theoretical models from literature. The COIL cutting performance is compared to referenced data of laser materials processing.

14 kW CW COIL has been modernized and tested. Experimental and numerical methods used for diagnostics and simulation of laser operation are presented, as well as results of experiments and numerical simulation.

The possibility to produce atomic iodine decomposing methyl iodide with the help of the vortex-flow DC glow discharge for use in oxygen-iodine laser has been investigated experimentally. Number density of iodine atoms had been measured via absorption of single frequency tunable semiconductor laser radiation at 1.315 μm. Two cases were studied: (1) the products of discharge in oxygen decomposed methyl iodide in the downstream afterglow; (2) methyl iodide was decomposed in the discharge plasma. Atomic iodine concentrations enough to operate oxygen iodine laser were obtained. In the first case iodine atoms number density up to 1.3•10¹⁵ cm^-3 was achieved for oxygen pressure 24 Torr. A kinetic model showing good agreement with experiment had been developed. In the second, vortex flow discharge stabilization permitted to sustain glow discharge in highly negative gas mixture that contained halogen, using Ar as carrier gas at pressures up to 20 Torr. Iodine atoms number density of 3.6•10¹⁵ cm^-3 was achieved at 15 Torr pressure of Ar.

The kinetics model of chemical oxygen-iodine laser (COIL) active medium taking into account EE, EV, VV, VT energy transfer processes was proposed. The O₂ molecule distribution on the vibrational levels in COIL was calculated. It is suggested that the involving of vibrationally excited O₂(a) into pooling reaction can increase the rate of stored in singlet oxygen electronic energy in COIL medium. Approximately 50% of relaxed O₂(a) energy transfers into thermal energy.

The vibrationally excited oxygen in O₂(a¹Δ_g)-I mixture was detected by emission spectroscopy. The analysis of a luminescence spectra of oxygen molecules on O₂(b¹Σ_g⁺,υ') → O₂(X³Σ_g^-,υ") transitions has shown, that vibrationally excited O₂(b¹Σ_g⁺) molecules up to υ=5 are generated in the active medium of chemical oxygen-iodine laser (COIL). The highest values of relative O₂(b¹Σ_g⁺,υ=1) population of 22% and O₂(b¹Σ_g⁺,υ=2) of 10% are reached for I₂ content in an oxygen flow ≈1%. It is shown theoretically, that the relative populations of O₂(X³Σ_g^-), O₂(a¹Δ_g) and O₂(b¹Σ_g⁺) molecules at the first and the second vibrational levels are approximately equal because of fast EE energy exchange between oxygen molecules. Up to 20% of oxygen molecules in COIL active medium are vibrationally excited.

It is experimentally shown that more than 20% of O₂ molecules in chemical oxygen iodine laser (COIL) active medium are vibrationally excited. Calculations show that approximately 4.5 vibrational quanta are formed under deactivating of one singlet oxygen O₂(¹Δ) molecule. Dependencies of threshold O₂(¹Δ) yield and gain on relative population of O₂(¹Δ,υ) are presented. The threshold O₂(¹Δ) yield increases with rising of the relative population of vibrationally excited oxygen and it can be some percents more than was considered before. The gain coefficient of COIL weakly depends on the degree of vibrational excitation of oxygen.

Results of simulations and experiments on a high-power double-pass explosively pumped photo-dissociation iodine laser (EPDL) with phase conjugation (PC) are presented. The laser system consists of a master oscillator, two exploding amplifiers with a working mixture 25 Torr C₃F₇I+125 Torr Xe and amplifier aperture of 15 cm, and an SBS-mirror. The SBS mirror consists of an angular selector of Stokes radiation, an ordered raster of small diffraction lenses, a main focusing lens, and an SBS cell. The calculation model and the computer code package take into account the actual three-dimensionality of space, transient effects at SBS, parasitic reflections of laser radiation from elements of the optical scheme, intrinsic amplified spontaneous emission of amplifiers, radiation losses in the optical path, non-uniformity of gain, and radiation refraction on optical non-uniformities of the active medium caused by a shock wave. In the laser system, an optimal configuration of the SBS mirror is used. It possesses unique properties if compared to the existing specimens of SBS mirrors. It stably gives a nearly ideal quality of PC at any level of SBS saturation, i.e. any reflection coefficient that has been confirmed by experimental laboratory investigations. As a result of investigations, a good agreement of calculated results with available experimental data has been demonstrated in energy, time dependence of power and Strehl number of output radiation. The considered EPDL has output energy of about 400 J and brightness of about 10¹² J/sr. It has been found that with the increase of the flux density of an input signal from the master oscillator in the range 0.01-20 W/cm² the brightness of EPDL output radiation increases as well whereas the full energy varies relatively slightly. It has been shown that parasitic reflections of laser radiation from the ends of amplifiers and elements of the optical scheme with a coefficient exceeding 10^-7 considerably decrease the axial brightness of output radiation. In order to reduce the harmful effect of parasitic reflections on brightness the distance between amplifiers should be increased.

Experimental research of various conditions for effective conversion of "Iskra-5" iodine laser radiation to the second harmonic (λ = 657.5 nm) were carried out. The influence of intensity, depolarization, divergence of main harmonic, optical quality of big aperture (size 32 x 33 cm) DKDP crystals, which are used for conversion and also angular error of their adjustment, was investigated. It was shown that the most essential factors, decreasing the conversion efficiency under Type II phase-matching condition are depolarization and small-scale noise of main harmonic radiation.

Being presented are the results of theoretical and experimental studies aimed at development of solar-pumped photo-dissociation laser fulfilled by RNTs "Applied Chemistry," Ioffe Physical Technical Institute and RFNC-VNIIEF. The model iodine laser concept was developed, and its parameters were calculated and experimentally optimized. The spectrum of xenon lamps was explored and its identical to solar spectrum features were demonstrated. The products of photolysis were studied in the active medium as well as the possibility of laser radiation conversion into the electrical one.

We report on the experimental status of the development of compact high power (up to 500 W) high repetition rate (up to 6 kHz) excimer lasers and discharge produced plasma sources radiating in an extreme ultraviolet (EUV) region. EUV power more than 70 W (around 13.5 nm wavelength, a bandwidth of 2%) into 2π sr at 1250 Hz was obtained for continuous operation of a source.

Experimental results of long-pulse generation in X-ray preionized XeCl lasers with a 9 x 7 cm² and 5.4 x 3 cm² apertures are described. Lasers operate at Ne-Xe-HCl mixture with pressure up to 4 atm. Paper-oil pulse forming lines and rail-gap switch for discharge pump was used. An 2 - 10 J output with optical pulse duration of 250 - 300 ns (FWHM) have been extracted. Problems and peculiarities of long laser pulse formation are discussed.

F₂-laser (λ = 157 nm) with 2 W average power and 100 Hz pulse repetition rate that worked at the gas mixture F2:He:Ne pressures below 3300 mbar has been investigated. Conditions of obtaining maximum laser efficiency dependent on the excitation system parameters were determined.

The behavior of high-purity fluorite crystals under the action of ionising radiation (fast electrons and roentgen) and also intensive KrF- and ArF-laser radiation has been investigated. On the basis of these experimental results and literature data the benefits of high-purity fluorite for manufacturing of windows and other optical elements for excimer lasers were demonstrated.

To verify experimentally the possibility of effective conversion of multi-line pumping radiation of HF chemical chain laser by the use of a combined active medium on the basis of buffered with inert gas (He, Ar, Kr, Xe) mixture of various isotopomers of CO₂ and N₂O the energy and spectral characteristics of CO₂-, N₂O- and combined CO₂-N₂O lasers with optical pumping were experimentally studied. Pumping of dense mixtures (P_total = 11 atm) containing CO₂: N₂O: (He, Ar) = (0-1):(0-1):10 by cascade P₁(8) and P₂(7) lines of HF laser with total energy ≈200 J was performed. Specific input energy reached 2 J/cm³ at pump radiation fluence up to 10 J/cm² and pulse duration of 1 μs. For the separate molecular components CO₂ and N₂O lasing with energies 4.3 and 8.9 J (input energies 47 and 104 J, respectively) in the spectral regions of (P- and R-) and P-branches was revealed. The CO₂-N₂O combined laser delivered emission with pulse duration ~ 30 ns in the region of overlap of R- and P-branches of N₂O and CO₂, respectively (wavelength 10.4 - 10.6 μm), with energy 12 J (200 J/1) equal to the sum of output energies on the individual components.

A two-color (λ₁ = 10.6 ÷ 11.3 μm and λ₂ = 5.3 ÷ 5.65 μm) laser with an original V-shaped cavity has been developed and experimentally realized. The radiation (λ₁ and λ₂) was coupled through the zero order of the grating along one direction. Production-type GL-501 (CO₂) and GL-509 (CO) electric-discharge tubes with non-transmitting mirrors were mounted at the shoulders of the three-mirror V-shaped cavity. The third mirror was a diffraction grating with 100 lines/mm, which was mounted at the cavity vertex and operated by the non-autocollimation scheme in the first order for the lasing on CO₂ molecules and in the second order for CO. As a result of the tuning of the diffraction grating, we obtained a stable oscillation on more than 30 pairs of lines (in the range of 10.6 - 11.3 μm for CO₂ and in the range 5.3 0 5.65 μm for CO) with the output power of ~10 W (CO₂) and ~1W (CO) for the strong lines at the single-mode regime.

Atmosphere pressure CO₂-laser with e-beam initiated disch arge formed in laser operating mixture has been created. Energy of radiation as 18 mJ in active volume of ~6 cm³ has been obtained. Laser operation at pulse repetition rate of up to 5 Hz was demonstrated. Specific energy input as ~0.1 J/cm³ was realized in gas mixture CO₂:N₂:He = 1:1:4 under atmosphere pressure in the process of a pulsed non-self-sustained discharge with ionized amplification. This method of discharge initiation is rather promising for creation of short-pulse high-pressure lasers.

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.

An automated laser technological complex (ALTC) based on a self-sustained transverse-flow discharge pumped CW CO₂ laser been developed. In the laser, a self-filtering optical resonator is used. The using of this type of resonator allowed to generate the high-quality beam with 8 kW power. The results of the beam characteristics measurements are presented. Power characteristics of the laser, filled with gas mixtures with or without helium, are presented. The maximum irradiation power amounts to 8.3 with extraction efficiency of 11.3, helium-free operation characterizes by the 5 kW power and 8,9% efficiency.

An H₂ - F₂ amplifier initiated by radiation from a pulsed hydrogen fluoride laser is studied theoretically. Numerical calculations are made by taking into account the inhomogeneity of initial HF concentration appearing upon preparation of the laser mixture in experiments. The dependence of the specific laser output energy from a distance x from the radiation input to the amplifier medium for mixture H₂:F₂:O₂:He = 100:600:30:100 Torr is obtained. Change of initial pressure of HF molecules in the mixture on the distance x was described by the expression p_o + Csin(2πx/d), where P_o = 0.1 - 0.5 Torr, d = 10 - 20 cm, C is the amplitude of deviation of HF pressure from its mean value. The theoretical specific output energy periodically depends on x according to the law of change of pressure HF. The energy gain (ratio of the energies of the output and initiating laser radiation) is equal to 5 for an amplification length 4 m at p_o = 0.1 Torr and C/p_o = 5%.

A new scheme of direct optical pumping of 4-μm HBr-laser was proposed being based on rather precise coincidence revealed of the principal 2P9 line of DF-laser with R2 line of the fundamental absorption band of molecular gas considered. Lasing at the use of off-axis pumping geometry (pump radiation flounce of 0.2 J/cm², duration ~300 ns) was observed within (0.4- 15) torr of HBr pressure range. The complex behavior of HBr-laser pulse intensity, duration and time delay on the gas pressure was analyzed. Energy conversion efficiency of ~2% was achieved at P~10 torr. It is believed that the one may be substantially increased by both the optimization of HBr-laser cavity losses and the use of the collinear pump geometry with improved mode-matching.

Mobile lidar complex provides monitoring of the atmosphere at the ranges up to 15 km in the wide spectral range from UV to mid IR. Three types of lasers are used for atmosphere probing via a common telescopic and scanner system. First tests of complex operability have shown high reliability of the equipment and realization of the main parameters.

In spite of fast evolution of the solid-state and fiber lasers, argon ion lasers remain to be the most powerful sources of short-wave CW radiation with high spatial coherence. At the same time, the active media of argon ion lasers -- low-temperature plasma -- is a good object for study nonlinear spectroscopic phenomena. In this work, the Autler-Townes doublet corresponding to the field splitting of ionic energy levels and the peak of EIT (electromagnetically induced transparency) induced by high-power radiation of the single-frequency argon argon laser have been studied. The effects are observed in the absorption spectrum at adajacent transition in 3-level Λ-scheme of ArII by probe-field technique. In the argon-laser plasma the shape of the EIT resonance is influenced by ion-ion Coulomb scattering. It leads to a broadening of resonant structures that is added to the field broadening. The measured EIT peak appears about 1.5 times wider than theoretical one taking into account corresponding power broadening. It is shown that the 1.5 times difference is due to the Coulomb broadening.

In this work the effects that appear in the optical breakdown are analyzed in water and the time dependences received also for the velocities and pressures at the wave fronts. The application of acoustic waves, generated by high power laser pulses in the aqueous medium, has quite serious perspectives for sounding. It is shown in the work that under comparatively low power density of radiation, as a result of a surface layer heating, the thermoelastic sresses arise, leading to the excitation of the acoustic waves. The analysis showed that the prognostic evaluations of the values of a light deflagration area are possible for a clear aqueous medium with the pressures up to 400 kg/cm². With the presence of microinhomogeneities, it is necessary to know their total physical and chemical properties and detailed trustworthy data by their spatial distribution. A principally new approach was developed to the problem of videoinformation transmission from the object surfaces by the fiber-optic channel. The application of a precision measuring TV-camera with a color format in the range 0.3 - 0.98 μm allows to raise the information capacity of the transmitted information. The optimization of vision module choice are considered also.

In this Report we present the results of theoretical and experimental investigations of photodynamics of optical limiting in the fullerene-containing media (solutions, solid-state microporous glasses and polymer layers), as well as in suspensions of fulleroid-type nanoparticles. Some prototype of nonlinear-optical devices on this base will be described as the examples.

C₆₀ and C₇₀-doped organic thin films (polyimide, 2-cyclooctylamino-5-nitropyridine, N-(4-nitrophenyl)-(L)-prolinol, Mg-phthalocyanine nanoparticles) and the polymer-dispersed liquid crystal compounds based on them have been studied under a laser irradiation at wavelengths of 532, 805, 1047, and 1315 nm. Mechanisms of the optical limiting effect in the fullerene-doped pi-conjugated organic systems have been discussed. Besides the reverse saturable absorption, an additional absorption due to complex formation has been established to be responsible for the phenomena mentioned above. It has been noticed that fullerene-doped organic structures can be used to attenuate the laser power in the visible and near infrared spectral ranges.

We have experimentally studied optical limiting in multi-component solutions containing polycyclic compounds (perylene and fullerenes) for which typical processe is photoinduced electron transfer with formation of ion pairs. Founded significant rise of limiting efficiency in such molecular systems is due to increase of absorption in the excited state. Formation of radical ions can be used for widening of spectral range of operating medium limiting.