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Chemical Oxygen Iodine Laser (COIL) is the shortest wavelength (1.315 μm) chemical laser employing singlet oxygen molecules as the pumping species and iodine atoms as lasing species. Singlet Oxygen Generator (SOG) is essentially the heart of this laser device which is basically a gas–liquid phase chemical reactor. SOG facilitates the reaction between a basic hydrogen peroxide solution (BHP, H2O2 + KOH) and chlorine gas to produce singlet oxygen molecules. Centrifugal Bubble Single Oxygen Generator (CBSOG) is a potential candidate for an alternative SOG with better operating conditions for high throughput and high power COIL systems. In CBSOG Chlorine gas is bubbled through a layer of BHP solution and the required reaction takes place at the gas–liquid interface of the formed bubbles under high speed rotation of the chamber for gravity independent operation. The performance of this device largely depends on the bubble formation characteristics and their traverse inside the BHP layer. The aim of this paper is to present the numerical analysis of the mechanics of bubble formation, detachment and movement in the BHP layer for different operating parameters as applicable to COIL. The determination of conditions for the transition from bubbling to the jetting regime at different centrifugal accelerations of high magnitude (G ∼ 204 g, 306 g & 387 g) with low liquid column thickness (∼6–8 mm) operating under low pressure (∼100 torr) is another point of focus. The Volume of Fluid (VOF) method has been used for the 3-D transient interface tracking between the phases. This paper also compares the simulation results for various gas flow rates and centrifugal accelerations with select experimental results reported elsewhere showing reasonably good agreement.

The rate constants for H2 -HF energy transfer processes, especially for those in vibrationally excited states, are very demanding in astrophysics and chemical laser engineering, especially for those in vibrationally excited states. Based on our recent potential energy surface, we used the coupled-states approximation including the nearest neighboring Coriolis couplings with energy-based local basis set to perform dynamics calculation for the H2 -HF energy transfer system. Rate constants for vibrational transitions (1; 3) → (0; 4), (1; 3) → (2; 2), and (0; 3) → (1; 2) were obtained. For state-to-state rate constants, transitions that have no internal angular momentum gap dominate at high temperatures. The vibrational-resolved rate constant for (1; 3) → (0; 4) initially decreases and then increases with the temperature, while those for (1; 3) → (2; 2), and (0; 3) → (1; 2) transitions monotonically increase. The calculated rate constants are in good agreement with the available experimental results. These dynamical data can be further applied to the numerical simulation of hydrogen fluoride chemical laser. © 2018 Wiley Periodicals, Inc.

The chemical kinetics of supersonic hydrogen fluoride (HF) chemical lasers determines combustion characteristics and output power. However, the inherent complexity of chemical reactions and complex structure still challenge the numerical simulations involving a comprehensive chemical mechanism. Therefore, a high fidelity and low computational consuming model is important for design purpose. This paper presents a strategy to generate a reduced mechanism for HF chemical lasers. Based on a detailed HF chemical mechanism consisting of 16 species and 153 elementary reactions, a specific skeletal mechanism including 11 species and 58 elementary reactions is generated. Finally, we obtain a further reduction mechanism including 11 species and 39 elementary reactions by combining sensitivity analysis and rate of production analysis. The computational cost for simulation of supersonic HF chemical lasers with the reduced mechanism is less than that with the detailed model. The principal contribution of the work is to provide a low computational consuming model.

An experimental study of combustion-driven HBr chemical laser based on D2/NF3 combustion was carried out. The exotherm of the reaction system was analyzed, and the thermal blockage issue of supersonic flow was solved by adjusting the buffer coefficient ω. By optimizing the laser operating conditions, a maximum HBr laser output of 141W was obtained, with the primary laser lines being HBr P1(5) , P1(6) , and P3(6).

A chemical flow reactor is used to study the vibrational population distribution of CO produced by a reaction between carbon vapor generated in an arc discharge and molecular oxygen. The results demonstrate formation of highly vibrationally excited CO, up to vibrational level v = 14, at low temperatures, T = 400–450 K, with population inversion at v = 4–7, in a collision-dominated environment, 15–20 Torr. The average vibrational energy per CO molecule formed by the reaction is 0.6–1.2 eV/molecule, which corresponds to 10–20% of reaction enthalpy. The results show feasibility of development of a new CO chemical laser using carbon vapor and oxygen as reactants.

The article focuses on the development of a data acquisition system (DAS) working in a noisy and hostile environment for an arc-operated hydrogen fluoride/deuterium fluoride (HF/DF) chemical laser. PC-based DAS has been configured using Advantech plug and play modules with fiber link connectivity. This article also focuses on implementation of an orifice-based precise gas flow control system. The plasma arc discharge in an arc heater/generator is essentially employed for inducing thermal dissociation of sulfur hexafluoride SF6 for production of fluorine atoms, and DAS has been used for performance optimization of the composition of the lasing mixture by independently varying the flow rate, pressure, and temperature of its constituents. Since arc load is complex with high voltage transients and electromagnetic noise, an optical fiber link has been implemented for data transmission. This article also discusses digital output interface circuitry for various electro-pneumatic actuators/solenoid valves. The de...

The exothermicity of the reaction between hydrogen and fluorine can be used for chemical processing, or in generation of HF based chemical laser, where higher temperatures are required. The ratio of H2 to F2 flow and the flow rate of nitrogen affect the reactor temperatures. The authors report their experimental and computational study on the effect of excess hydrogen and nitrogen flow on reactor temperatures in a tubular reactor. The experiments have been performed over a wide range of flow ratios to generate reliable data for reactor scale-up. The computational studies predict the temperature, velocity, and species concentration at different locations of the reactor. The temperature predictions show a good match with the experimental findings. This study may be helpful in designing a large scale H2-F2 flame reactor.

A cryogenic adsorption technique was presented to replace the machinery pump and exhaust processing system,which could provide a possible way to greatly suppress the size of a discharge-driven CW HF/DF chemical laser.As the nitrogen diluent must be used instead of helium for the cryogenic adsorption pump,the efficiency of HF/DF chemical laser would be lowered down greatly.To solve the problem,a periodically arranged supersonic nozzle array composed of slit and conical holes with a 4 mm period was developed to replace the traditional single slit transverse sonic fuel injecting gain generator.Experimental results with HF laser demonstrates that the laser output and electrical-optical efficiency by designed supersonic nozzle array have been increased from 25 W to 90 W,and 0.8% to 5.9%,respectively.Furthermore,the fuel specific efficiency has a nearly fourfold increase,which is slightly higher than that from the helium diluen.Obtained results prove that the efficiency of the nitrogen diluted discharge-driven CW HF/DF chemical laser can be greatly improved by using the devel-oped supersoinc nozzle array.

To study the starting characteristic of directly drained CW DF/HF chemical laser (DDCL), a double-nozzle small-scale model of DDCL gas channel was set up, and a series of experiments without secondary flow was conducted with nitrogen and helium as primary flow respectively. The data of experiment, which is conducted with nitrogen and primary nozzles of large area ratio, are far away from the theoretical result. It is believed that, a part of nitrogen has phase transition while it is expanding in the experiment, and then the one-dimension treatment is out of place. In addition, the states of cavity fuels and secondary diluent helium will not change in a CW DF/HF chemical laser, but the area ratio of secondary diluent nozzle must not be very large if the secondary diluent is nitrogen.

The efficiencies of different fuel compositions used in the combustion chamber of an autonomous cw chemical HF—DF laser for obtaining high specific energy parameters during simultaneous lasing in HF and DF molecules in two spectral ranges are theoretically analysed. It is shown that mirrors with the reflectance above 99% in these spectral ranges can be manufactured in principle.

By using the concept of a high-pressure, gravity-independent singlet oxygen generator (SOG) proposed by Emanuel and based on the principle that a rotating fluid is capable of producing an enormous centrifugal force, a novel-type centrifugal-flow singlet oxygen generator (CFSOG) was designed and constructed. In this device, O2(1Δ) was generated in the reaction of gaseous Cl2 with a rotating basic hydrogen peroxide (BHP) liquid flow and then was removed from the BHP liquid phase by the centrifugal force. Meanwhile, the microdroplets formed during the Cl2+BHP reaction were removed from the O2(1Δ) gas flow by the centrifugal force produced by the high-speed flow along an arc-shaped channel. Preliminary investigations showed that, because the specific reactive surface area of this SOG was noticeably larger than that of the jet-SOG normally used in current chemical oxygen–iodine lasers (COILs), the O2(1Δ) yield of ~60%, the O2(1Δ) partial pressure as high as 31 Torr, and chlorine utilisation higher than 96% were realised. Moreover, steady operation was obtained.

This paper presents results from investigations of chemically reacting flowfields and optical gain profiles in HF chemical laser media by infrared hyperspectral imaging. Subsonic and supersonic chemiluminescent F+H2 reacting flowfields, produced in high-fluence microwave-driven reactors, were imaged at a series of wavelengths, 2.6-3.1 microm, by a low-order, spectrally scanning Fabry-Perot interferometer mated to an infrared camera. The resulting hyperspectral data cubes define the spectral and spatial distributions of the emission. Spectrally resolved images at high spatial resolution were processed to determine spatial distributions of the excited-state concentrations of the product HF(v, J) molecules, as well as spatial distributions of small-signal gain on specific laser transitions. Additional high-resolution Fourier transform spectroscopy and spectral fitting analysis determined detailed excited-state distributions in the reacting flowfields. The measurements showed that energetic HF(v, J) state distributions were generated by both the supersonic and fast-flow subsonic mixing schemes. In particular, the subsonic reactor produced a spatially distributed field of inverted, near-nascent state populations, with small-signal gains near 2-3%/cm.

There is always a challenge on large aperture medium power laser’s resonator design, stable resonator would supports significant higher order transverse modes, folded and telescope stable resonator are too complex and not preferred by engineers, unstable resonator need rather large round trip gain to compensate its high geometric out-coupling, which is difficult for this kind of laser since its gain length is limited due to the power level and large aperture. Partial feedback unstable resonator had been proposed to tackle this difficulty since the early days of laser development, however, the debates of its effect never stopped even with those distinguished optical resonator scientists such as Siegman, Anan’ev, and Weber. Recently integrated partial feedback unstable resonator design had been successfully demonstrated on a medium size chemical oxygen iodine laser. In this paper, we carry this resonator configuration on a small scale discharge driven supersonic nozzle array Hydrogen Fluoride chemical laser, a typical large aperture short gain length device. With magnification equals 4/3, we successfully get ten Watts level ring beam output.

An optical cavity temperature test method has been established for the HF chemical laser. This method assumes that in HF optical cavity the rotational distribution of vibrationally excited HF molecules meets the statistical thermodynamic distribution, the first overtones (v = 3-1 and 2-0) spontaneous emission spectral intensity distribution is obtained by using OMA V, the optical cavity temperature is calculated by linear fitting the rotational thermal equilibrium distribution formula for each HF vibrationally excited state. This method is simple, reliable, and repeatable. This method can be used to test the optical cavity temperature not only without lasing, but also with lasing.

Under cavity loss modulation, enormous dynamic behaviors will come up in B type cascade laser. In this paper, we built a two-wavelength cascade transition balanced equation model for CW HF chemical laser, 2P(5) and 1P(6) line were taken as cascade pair. We carried out cavity loss modulation experiment on a small scale supersonic discharge driven hydrogen fluoride chemical laser. From the view of phase space, we explained the characteristics by nonlinear time series analysis tools.

The energy parameters of an HF laser operating by using a new method for oxidising-gas production, which is based on the principle of two-region mixing, are optimised. The total amount of the inert diluent (helium) supplied to the laser was varied during experiments by varying its relative fraction only in the second mixing region. For an optimal relative fraction of the diluent in the second mixing zone and for an optimal position of the optical axis of the cavity under a constant pressure in the gas generator, the laser radiation power and the specific power output could be increased by 50% and 60%, respectively, compared to the laser operation regime realised in our previous experiments. In this case, the inert diluent amount decreased by 35% and the length of the generation region increased by 20%.

The consequences of replacing the primary fuel, hydrogen, as a part of the conventional F2 — H2 — He DF-laser fuel composition by ethylene are studied experimentally. During comparative tests of the laser with different primary fuels, the completeness of combustion of the fuel mixtures is assessed and their optimal chemical compositions, at which the energy and spectral characteristics of laser radiation are measured, are determined. It is shown that, when C2H4 is used instead of H2, an increase in the specific laser energy yield of 37 % without a change in the active-medium length is ensured and radiation within the range of 3.75 — 4.18 μm is generated.

This This Al2O3, SiO2, Ta2O5, Nb2O5, TiO2 single layer oxide thin film are prepared by using ion beam sputtering deposition technology. The oxide films infrared optical constants are fitted by infrared variable elliptic polarization Angle spectrum instrument (IR - VASE), the results show that the fitting optical constants n, k in line with the material properties. The oxide thin film surface roughness are analyzed by AFM (Nanosurf Easysc -2), and research findings show the compact structure of oxide film and RMS of surface roughness in 0.1 nm, which scattering is smaller. The main working band of infrared detector and chemical laser are in the infrared 2-6 µm band. The application of the optical thin film material is mainly fluoride, sulfide and selenite soft membrane materials in infrared wavelengths. Oxide has been widely used in visible near infrared wave band with the superior mechanical properties and environmental stability, and prepared for high performance optical thin film. But research and application of infrared wavelengths in oxide are rarely reported. It is of great significant to widen the application range of the oxide film, and solve the traditional infrared thin film material environmental stability and poor adhesion. 2. Experimental Experiment coating equipment of ion beam sputtering coating machine produced by United States Veeco company .Coating target materials and the purity are respectively: SiO2 (99.999%), Al (99.999%), Ta (99.99%), Nb (99.95%), TiO2 (99.99%), target size is about 35.5 cm (14 inches). Experimental background of vacuum are under 5 x 10 -4 pa, the pressure in the process of coating remain at around 4.2 x 10 -2 pa.

The dependence of the energy parameters of an oxygen — iodine chemical laser with a bulk generation of iodine atoms in a longitudinal electric discharge on the length of the discharge gap is studied for various discharge energies and voltages and various working mixture compositions (at constant oxygen and iodine pressures). Analyses of the results suggests that temperature effects account for a twofold decrease in the specific energy yield for the lasing initiated by a longitudinal electric discharge compared to the photolytic initiation.

CW laser action has been demonstrated on the electronic I ∗ ( 2 P 1/2 ) → I( 2 P 3/2 ) transition of atomic iodine at 1.315 μm from the NCl (a 1 Δ )+I( 2 P 3/2 ) energy transfer reaction. The stimulated emission was generated in a transverse subsonic flow device when hydrogen azide, HN 3 , was injected into a flow of iodine and chlorine atoms. The measured laser output power was 180 mW.

A chemical oxygen-iodine laser (COIL), the VertiCOIL device, was transferred from the Air Force Research Laboratory (AFRL) to the University of Illinois at Urbana-Champaign (UIUC) and made operational. The performance of the high-power VertiCOIL laser was measured with nitrogen diluent, New nozzle designs were investigated and implemented to optimize nitrogen performance, Nitrogen diluent chemical efficiencies of 23% were achieved; these are the highest reported chemical efficiencies with room-temperature nitrogen diluent. A long duration, high chemical efficiency test was demonstrated with nitrogen diluent; a chemical efficiency of 18.545 at 30 mmol/s of chlorine was maintained for 35 min. The highest performance was obtained with new iodine injector blocks and a larger throat height. The new iodine injector blocks moved the injectors closer to the throat by 0.7 cm and the throat height was increased from 0.897 to 1.151 cm (0.353 to 0.453 in). The performance enhancements were in qualitative agreement with the system design predictions of the Blaze II chemical laser model. Three-dimensional computational fluid dynamics calculations using the general aerodynamic simulation program code confirmed the principle design change of moving the iodine injectors closer to throat.

Results are presented from a study of HF lasers pumped by non-chain chemical reactions initiated by a radially convergent and by a planar electron beam. The main channels of formation of vibrationally excited HF molecules are analyzed. The distribution of the energy density of the radiation in the output beam of a wide-aperture laser is measured. In 30 liters of a mixture of SF6:H2=8:1 at a pressure of 1.1 atm an output energy of ∼200 J is obtained at an ∼11% efficiency with respect to the energy deposition. It is shown that the admixture of a buffer gas of neon or argon improves the uniformity of the radiation energy distribution in the output beam of an HF laser pumped by a non-chain chemical reaction and initiated by an electron beam, and it also increases the output energy.

Ordered volume nanocompositions are obtained by exposing a colloidal aqueous solution of albumin with carbon nanotubes to cw IR laser radiation. Nanocompositions contain spherical and toroidal globules of size 100–500 nm with electric properties inherent in conglomerates of coiled nanotubes. The hardness of the material obtained depends on the irradiation intensity and time, and its consistence can be varied from pasty to glassy.

It is assumed that both translational and rotational nonequilibrium cross-relaxations play a role simultaneoulsy in low pressure supersonic cw HF chemical laser amplifier. For two-type models of gas flow medium with laminar and turbulent flow diffusion mixing, the expressions of saturated gain spectrum are derived respectively, and the numerical calculations are performed as well. The numerical results show that turbulent flow diffusion mixing model is in the best agreement with the experimental result.

Abstract Downhole operations in the petroleum industry include drilling and completing the well for production. Experiments conducted on different types of lasers have shown the potential of the cutting - edge technology being applied in downhole operations. One of the tests was conducted on MIRACL (Mid Infrared Advanced Chemical Laser) to determine its feasibility for drilling and perforating petroleum wells and another was on COIL (Chemical Oxygen-Iodine Laser) to determine the least specific energy (SE) needed to destroy varying rock types. This paper presents the applications of laser technology in downhole operations such as drilling, perforation, stimulation, vaporizing stuck pipes, tracer detection, treatment of asphaltene deposition and cutting of subsurface equipment such as casings, tubing strings etc. Its benefits are presented in terms of effects on Rate of Penetration (ROP), operational downtime, formation damage, clay treatments, flow enhancement and overall well deliverability. Laser technology has been utilized successfully in the medical industry, manufacturing industry, nuclear industry etc. Therefore, its applications in downhole operations are major strides in the petroleum industry and a means of optimizing downhole operational practices. It has been reported that integrating laser technology with conventional drilling technology will immensely improve drilling efficiency but this has not been so far applied in the field. Conclusions derived from a two year project funded by The Gas Research Institute (now Gas Technology Institute) in 1997 on "Adapting Star Wars High-Powered Lasers to Drilling Natural Gas Wells," are that lasers can cut rock of all lithologies; shear power shares importance in cutting rock with such parameters as wavelength, purge gas pressure and hole size; and historical and widely accepted theoretical calculations of the laser power needed to spall (break), melt and vaporize rock are significantly higher than experimental values. Just like any new technology, laser technology has its challenges and they are highlighted accordingly. Introduction The most reliable way to detect oil and gas is by drilling an oil well. From the onset, oil wells have been drilled using cable tool (percussive) drilling method. This method of drilling was gradually replaced by rotary drilling in the twentieth century. As Research and Development progresses, laser drilling was developed in the 90's. An oil well needs to be completed to flow the well. Well completion includes casing, cementing, perforation, stimulation etc. Various studies have been conducted to evaluate the suitability of this breakthrough technology in downhole operations and they have all yielded positive results.

Angular distributions are measured for individually resolved ν‘, j‘ states of HF produced by F + H2 → HF(ν‘ = 1, j‘) + H and F + H2 → HF(ν‘=2, j‘) + H reactive collisions in a crossed-beams scattering apparatus. Simultaneous resolution of the HF vibrational and rotational states is achieved spectroscopically for the first time, using laser excitation in conjunction with bolometric detection. The technique is sensitive to population differences between ν‘ = 1, j‘ and ν‘ = 2, j‘ − 1 states optically coupled by specific P2(j‘) lines of a vib-rotational chemical laser. The measurements are greatly facilitated by the development of a new high-temperature atomic fluorine beam source, which exhibits excellent stability, very high intensity, and narrow velocity distributions. Features common to individual product rotational states are as follows: strong backward scattering into ν‘ = 2, j‘; weaker backward scattering into ν‘ = 1, j‘; and heretofore unobserved scattering into ν‘ = 1, j‘ in the forward hemisphere. ...

Kinetic measurements of NCl(a1Δ) metastables produced by the photolysis of chlorine azide (ClN3) at 193 nm are reported. High NCl(a1Δ) density (>1015 molecules/cm3) production facilitates measurements of the NCl(a1Δ) + NCl(a1Δ) self-annihilation rate. A gas phase transient chemical titration scheme is used to calibrate absolute NCl(a1Δ) density. The NCl(a1Δ) bimolecular rate coefficient at room temperature is (7.2 ± 0.9 × 10-12 cm3/(molecule s) and has a magnitude very critical to the development of an NCl(a1Δ) + I(2P3/2) → I*(2P1/2) + NCl(X3Σ-) chemical laser. Despite the large value of the self-annihilation rate, intense I*(2P1/2) emission via transfer from NCl(a1Δ) is strongly observed when mixtures of CH2I2 and ClN3 are photolyzed at 193 nm. Unlike the analogous O2(a1Δ) + I(2P3/2) energy transfer system, the relatively large NCl(a1Δ) bimolecular rate constant suggests that NCl(a1Δ) transport times must be short and will require small chemical mixing regions for efficient lasing. In addition, the 300 K...

The performance of an electric discharge, plasma-cathode-preionized, atmospheric-pressure HF chemical laser was investigated and the laser was geometrically optimized. The preionization electron density was measured at atmospheric pressure in helium and in a mixture of SF 6 + H 2 diluted by helium. The measured preionization density is n e ≈ 6.7 × 10 9 −2 × 10 10 cm −3 , which is higher than the minimum critical density required for a self-sustained, homogeneous discharge of atmospheric-pressure electronegative gases. We have found improvement in laser specific energy for a diluted gas mixture of SF 6 + H 2 due to reduction in SF 6 concentration. The effects of inter-electrode gap height and plasma cathode grid width on laser performance were also investigated and are reported.

Chemical laser propulsion (CLP) is accompanied by the release of chemical energy in the process of laser propulsion, which can improve laser propulsion performance. In this article the propulsion performance of POM propellant under the constraint of a cylindrical tube-type thruster in atmospheric and nitrogen environments, respectively, has been conducted experimentally. The results indicate that the ablation masses of a single pulse under two gas environments are close, but the momentum coupling coefficient C m and specific impulse Isp in atmospheric environment are higher than that in nitrogen environment, which demonstrates an exothermic reaction occurred between the ablation product and the environment oxygen. To learn the mechanism of CLP the molecular spectra for ablation products of POM propellant in atmospheric and vacuum environments are measured and analyzed, respectively, and it reveals that the final product in a vacuum is CH 2 O, while the final products are CO 2 and H 2 O in the atmosphere. Then the chemical reaction, composition and chemical energy release have been confirmed in the atmospheric environment. By using Arrhenius finite rate chemical reaction model with the code Fluent the flow field evolution of ablation product was simulated numerically. The results show the intensity of chemical energy release is related to the contact and mixing degree of the ablation product and the oxygen in the atmosphere, mixing more fully, the chemical energy released more intensively.

An investigation was made of the operation of a chemical laser based on a photoinitiated chain reaction of fluorine with hydrogen (deuterium) in a master oscillator—amplifier configuration. The experiments showed that it was possible to achieve an energy efficiency of ~100% in the amplifier. Studies were made of the spectral characteristics of the system and the divergence of the radiation was determined. Equations describing quasi-cw operation of a monochromatic laser were found to be capable of providing satisfactory quantitative estimates of the energy characteristics of the radiation from this chemical laser operating as an amplifier or in the free-running mode. The estimates agreed with the experimental results when the initiation power was varied.

A controlled and readily reproducible thermolysis of silane (SiH 4 ) entrained in both an argon and helium carrier is used to form the precursor whose oxidation prepares long-lived yet readily monitored SiO b 3 Π metastables in high yeild. A simple yet novel pyrolysis-N 2 O oxidation source produces the b 3 Π metastables, yet no evidence is obtained for the formation of the lower-lying SiO a 3 Σ + state. This result, which is in sharp contrast to observations made when an oven generated, helium or argon entrained silicon beam is oxidized with N 2 O, suggests either an unusual symmetry constraint and selective reaction branching to the b 3 Π state or the highly efficient quenching of the a 3 Σ + state. This implies that a surprisingly similar quenching of the a 3 Σ + state must occur in distinctly different helium or argon diluted silane based environments. An analysis of the observed SiO A 1 Π- X 1 Σ + and b 3 Π- X 1 Σ + emission band systems produced with the silane based source demonstrates that the SiO b 3 Π state is formed apparently selectively in a ratio exceeding 2200 times that of the remaining SiO excited states. The results obtained with the present pyrolysis N 2 O source are contrasted to the continuous chemiluminescent emissions associated with thermalized silane-ozone and silane-oxygen reaction environments.v The current means of generating SiO metastables would appear to (1) allow the creation of a long path length medium for the efficient energy transfer pumping of visible chemical laser amplifiers and oscillators and (2) form the basis of a useful method for the control and efficient monitoring of SiO surface deposition processes.

Experimental study of a pulsed, electric-discharge-initiated, SF/sub 6/+H/sub 2/ pumped HF chemical laser is presented. The reactants were premixed and the laser medium was preionized by means of a plasma cathode. The laser pulse energy, as a function of the discharge voltage, was measured for various laser medium parameters. It was concluded that the ratio between the width and height of the active volume is an important issue in the laser performance.

The possibility of using fluoro-organic hypofluorites (CF3OF or CF2(OF)2 as a source of atomic fluorine for hydrogen oxidation in the working mixture of HF-chemical lasers, with pulsed CO2-laser pumping, was proved theoretically and experimentally. The results suggest an increase of the generation energy due to the chain reaction energy developed in the chemical laser working mixture.

A supersonic all gas-phase iodine laser driven by NF 3 /D 2 /DCl/CF 3 I combustion has been experimentally studied. the gain signals of I( 2 P 3/2, F=4)← I( 2 P 1/2 ,F=3) at 1315.246nm and I( 2 P 3/2 ,F=3)← I( 2 P 1/2, F=3) at 1315.222nm were observed with an intensity of 3x10 -5 cm -1 and 1x10 -5 cm -1 respectively. The small signal gain of I( 2 P 3/2 ,F=4)← I( 2 P 1/2 ,F=3) at different location relative to HN 3 injector along the flow direction also was obtained. The experimental results indicate that the AGIL driven by NF 3 /D 2 /DCl/CF 3 I combustion is feasible.

Efficient Nitrogen diluted HF/DF laser with cryogenic adsorption provides a possible way to realize compact and relative high power mid-infrared laser system. Driven by only one dc-discharge tube, 117 Watt laser power, total e-o efficiency of 6.6% in HF case, and that stands four to five-fold increase had been achieved with Nitrogen dilute by careful designed supersonic nozzle array gain generator. Spectra, gain distribution, and chemiluminescence are further investigated to explain the enhancing mechanism.

]HF chemical laser with MOPA configuration is a good solution to achieve high output power with high reliability. Kinetic models for HF amplifier are important for prediction and optimization of the performance of MOPA chemical lasers. In this paper, a simplified model for HF chemical laser amplifier is presented. The main processes which are included in the model are: (a) chemical pumping of HF (v=2) and HF (v=1), (b) stimulated transitions and spontaneous emission. (c) relaxation of vibration excited HF molecule by H 2 ,N 2 and HF. Some assumptions are taken in this model: (a) the density of H 2 , N 2 , HF, translational temperature and velocity of gas mixture are averaged across the laser cross section, (b) only two vibration-rotational transitions (2P6, 1P7) occurs in the amplifier, (c) gas temperature does not change during the lasing process in the amplifier. Based on these assumptions, a set of three-level rate equations is formulated and then solved by an iterative technique. Comparison is made with recent experimentally obtained data from a low power discharge-driven CW HF laser with MOPA configuration. It is shown that experimental results are consistent with the calculation from the simplified model.

HF chemical laser with master oscillator power amplifier (MOPA) configuration is a good solution to achieve high output power with high reliability and good beam quality. Researches of spectrum on HF chemical lasers with MOPA configuration are important for both enhancing atmospheric transmission and ensuring high power extraction efficiency on multiple vibrational transitions. A HF chemical laser operated in the line-selected mode which makes the output frequencies located in the atmospheric transparency windows will allow low atmospheric absorption, which will reduce thermal blooming effects and increase the intensity on the target. This will make the CW HF chemical lasers a possible development for long-distance transmission within the atmosphere. In this paper, a HF chemical laser with MOPA configuration using two identical discharge-driven CW HF laser modules as the laser oscillator and amplifier is presented. A multiple-selected-line, confocal, unstable resonator is also introduced. Measurements of spectrum on the laser have been taken by varying the flow parameters of the discharge-driven HF laser. It is concluded from our experiments that, the spectrum keeps stable with fixed flow parameters, even though the relative power of different lines varies slightly, and the maximum power is on the direct cascade of P 2 (7) and P 1 (8) lines. It is also believed that control of the flow parameters may allow high J direct cascade levels transitions, which may ensure high power extraction efficiency from multiple vibrational transitions.

HF chemical laser with MOPA configuration is a good solution to achieve high output power with high reliability. Kinetic models for HF amplifier are important for prediction and optimization of the performance of MOPA chemical lasers. In this paper, a simplified model for HF chemical laser amplifier is presented. The main processes which are included in the model are: (a) chemical pumping of HF (v=2) and HF (v=1), (b) stimulated transitions and spontaneous emission. (c) relaxation of vibration excited HF molecule by H2,N2 and HF. Some assumptions are taken in this model: (a) the density of H 2 , N 2 , HF, translational temperature and velocity of gas mixture are averaged across the laser cross section, (b) only two vibration-rotational transitions (2P6, 1P7) occurs in the amplifier, (c) gas temperature does not change during the lasing process in the amplifier. Based on these assumptions, a set of three-level rate equations is formulated and then solved by an iterative technique. Comparison is made with recent experimentally obtained data from a low power discharge-driven CW HF laser with MOPA configuration. It is shown that experimental results are consistent with the calculation from the simplified model.

A novel shock tube reactor was used to pulse heat a gaseous mixture of He, FN3, and Bi(CH3)3 along a 40 cm optical path between two highly reflective mirrors. Production of NF(a1Δ) by dissociation of the azide was found to occur in a ‘‘delayed avalanche’’ approximately 50 μs after shock reflection, and weak lasing at 470 nm was observed that is assignable to electronic transitions in the BiF(A–X, Δv=3) band.

A thermodynamic approach to the problem of the maximum efficiency for a chemical laser is developed. Assuming the laser radiation entropy to be negligibly small in comparison with the entropy of the chemically reacting compounds, the thermodynamic limitations for the laser efficiency are obtained. A number of kinds of chemical reactions, each one being a source of laser pumping, are explored. It is shown that the most significant restrictions appear for reactions of recombination type reducing the number of particles in the laser mixture. Photorecombination lasers are investigated in detail. The maximum efficiency for those lasers is computed over a wide range of proposed parameters of the initial mixture.

The characteristics of an all gas-phase iodine laser (AGIL) that uses molecular iodine as a source of iodine atoms is studied. The laser is based on the energy transfer reaction between metastable NCl(a1Δ) and ground state I(2P 3/2) atoms, which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of the chemical species, the laser output powers are measured at three different positions in a flow reactor. The output power is characterized by a function of the optical axis position and is reasonably reproduced by the numerical calculation. A repetitive pulse of laser output at 50 Hz with a duty factor of 40% is observed. The highest output power is 40 mW at 210 mm downstream from the mixing point of I/H/He and NCl3. This is 80% of the output power generated from the conventional system using HI as an iodine donor. The measured results of the time resolved laser output power suggest that the output power of the I2- AGIL is more sensitive to the electric discharge plasma intensity as compared to that of the HI-AGIL. An AGIL operated using I2 could potentially have the same output power as that of an AGIL operated using HI if a continuous-wave electric discharge generator is used.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Output power enhancement of an all gas-phase iodine laser (AGIL) by addition of hydrocarbon gases is studied. It is expected because hydrocarbon gases might scavenge Cl atoms, which are strong quencher of the upper state of the laser medium, I( 2 P 1/2 ). In AGILs, suppression of the Cl atom concentration is the key to improving the efficiency of laser operation because Cl atoms are inherently generated by the self-annihilation of the energy donor, NCl(a 1 ' ). We found that the addition of CH 4 gave the best results because of its high scavenging rate constant and inertness to I( 2 P 1/2 ). An enhancement of 10% was observed in the output power when CH 4 was added at a flow rate twice that of NCl 3 . On the other hand, when C 2 H 4 or C 2 H 2 were added at the same flow rate as that of CH 4 , the output power reduced despite their fast removal rate of Cl atoms. The reason for the reduced output power was that the unsaturated bonds scavenged not only the Cl atoms but also the H atoms, resulting in a low density of H atoms, and this decelerated the production of NCl(a

The optical performance of antireflection coatings on alkaline earth fluoride window materials at DF chemical laser wavelengths is presented. Reported coating absorption losses are less than 0.01% per surface. Those material properties that are important for this application are discussed, and theoretical coating designs are compared with experimental results.

The optical absorption has been measured at DF and HF wavelengths in a wide variety of transparent materials that show promise for use as windows on high powered chemical lasers. These measurements, which were made using DF-HF chemical laser calorimetric methods, will be discussed in terms of surface and bulk contributions to the total absorption as well as in terms of the total absorption measured for each type of material studied. Materials studied include the alkaline earth fluorides, alkali halides, Ge, Si, ZnSe, MgO, Yttralox, and A1(2)O(3).

Theoretical and experimental studies of the amine-based all gas-phase iodine laser (AGIL) are conducted. The numerical simulation code is a detailed one-dimensional, multiple-leaky-stream-tubes kinetics code combined with all the known rate equations to date. Using this code, we find that the key reactions to achieve positive gain are the deactivation reaction of excited iodine atoms by chlorine atoms and the self annihilation reactions of NCl( 1 Δ). The order of the injection nozzles is crucial to suppress these reactions. Following the calculations, we fabricate a flow reactor apparatus and demonstrate laser action for the 2 P 1/2 - 2 P 3/2 transition of iodine atom pumped by energy transfer from NCl( 1 Δ) produced by a set of amine-based, all gas-phase chemical reactions. Continuous-wave laser output of 50 mW with 40% duty factor is obtained from a stable optical resonator consisting of two 99.99% reflective mirrors. The observed laser characteristics are reasonably explained by numerical calculations. To our knowledge, this is the first achievement of amine-based AGIL oscillation.

The gain dependence on time of the HCl chemical laser was measured and calculated. Comparison of the calculated and measured results enables one to determine the constant of HCl-HCl deactivation which is found to be within (0.2-9) 10(12) cm(3) mole(-1) sec(-1).