The NCl-I laser has been demonstrated using HN3 as a fuel. In this paper, we discuss the possibility of constructing a NCl(a1Δ)-I transfer laser using NCl3 as a fuel. Not only is NCl3 more stable, but also may eliminate the requirement for a combustor. We present kinetic modeling and some initial results of experiments designed to understand the basic physical processes in this system.
Singlet Oxygen Generator ( SOG ) with a novel approach has been designed and fabricated. Singlet oxygen is taken out of the SOG at an angle of 40° thus avoiding the carry over of droplets, which is one of the major drawbacks of horizontal system. The paper discusses various design parameters for such type of SOG. For flow rates of chlorine up to 22 mmol/sec, the chlorine utilization and singlet oxygen yield have been observed to be ~ 90% and ~64% respectively.
We present preliminary results of an effort to develop an ultra-sensitive, diode laser-based diagnostic for NCl(X), an important species in the all gas phase iodine laser. This system uses a narrow band, tunable diode laser to probe transitions within the (0,0) band of the NCl(b - X) system near 662 nm. We provide a description of our detection and calibration strategies and present initial calibration results.
A study of recently proposed chemical method of atomic iodine production in the Chemical Oxygen-Iodine Laser (COIL) was performed. The process using gaseous reactants is based on the fast reaction of hydrogen iodide with chemically produced atomic chlorine. In the absence of singlet oxygen, the high yield of atomic iodine was attained (80 to 100 %). In the flow of singlet oxygen, the gain of 0.32 % cm-1 on 3-4 transition in iodine atom was achieved. It was found that both the rate of atomic iodine generation and gain depend substantially on mixing conditions of reacting gases. In laser experiments, effects of ratio of reactants, and their dilution by nitrogen on the laser output power were studied. The output power of 285 W was attained at chlorine flow rate of 27 mmol s-1 corresponding to chemical efficiency of 11.7 %. It was the first time when gain and laser output power were achieved in the COIL with atomic iodine generated by the proposed method.
Singlet oxygen generators for COIL devices that involve discharge or optical excitation are currently being investigated. These generators deliver relatively high yields of O2(b1Σ+) as the flows do not contain water vapor. In addition, discharge generators provide high concentrations of O atoms. Dissociation of I2 by the reagent streams from these generators will follow different kinetic pathways than those that are most important when the flow from a chemical generator is used. To provide a basis for understanding the dissociation kinetics that will be relevant for discharge and optically driven COIL devices we have examined the quenching of O2(b) and O2(a) by I2. Dissociation of I2 by atomic oxygen and I*+O quenching have also been investigated. The primary findings are: (1) Quenching of O2(b) by I2 is fast (5.8x10-11 cm3 s-1) with a branching fraction of 0.4 for the channel O2(b)+I2→O2(a)+I2. (2) Quenching of O2(a) by I2 is too slow (k<5x10-16 cm3 s-1) to be the initiation step in the I2 dissociation process. (3) O2(a) is generated when I2 is dissociated by O atoms. (4) The upper bound for the rate constant for quenching of I* by O atoms is k<5x10-12 cm3 s-1.
The demonstration and characterization of a multi-watt All Gas-phase Iodine Laser (AGIL) are described. A 20-cm subsonic reactor was used to produce NCl(a1Δ) for a series of parametric studies of the I*(2P1/2)-I(2P3/2) small signal gain and extracted power dependence on reactant flow rates and reaction time. The highest measured gain was 2.5x10-4 cm-1 and the highest power observed was 18 W.
In this paper we describe a novel, ultra-sensitive diode laser based diagnostic for small signal gain in atomic iodine based laser systems. We describe the overall diagnostic design and present initial data on the sensitivity of the device.
Laser medium parameters of multi-kW grid nozzle supersonic Chemical Oxygen Iodine Laser (COIL) were experimentally studied. Small-signal gain (SSG) diagnostics was done by a narrow line width tunable laser by scanning 1 GHz range around (2P1/2 ) - (2P3/2) spin-orbit transition line of atomic iodine. SSG was investigated as a function of Mach number and gas flow rates. Modeling of gain for different flow conditions was done as well. Multi-kW COIL device was recently developed in Miki Pulley Co., Ltd. (Japan) and has 37.5 cm length of active medium.
Modeling studies have shown that fractions of O2(1Δ) may be produced in an electrical discharge that will enable oscillation of a chemical oxygen-iodine laser system in conjunction with injection of pre-dissociated iodine. Results of those studies along with recent experimental results indicate that generation of O2(1Δ) can be optimized by the addition of flow diluents and select choice of process parameters. The model predicts the experimentally observed spatial decay of O2(1Σ) and shows reasonable agreement with experimentally observed temperatures.
To assist in the design and development of high power Hydrogen Fluoride laser systems Aculight has developed a novel, compact, widely tunable spectroscopic source specifically for operation in the 2.4 to 2.8-micron wavelength region. This source is a continuous wave (CW), room temperature, single frequency, diode-pumped, doubly resonant optical parametric oscillator (DRO). The spectroscopic capabilities of the OPO have been demonstrated by scanning its frequency through absorption features of carbon dioxide at 2.7 microns. We have also characterized the effects of water vapor absorption in this wavelength region upon the performance of the source. In addition to measuring key HF laser parameters this widely tunable mid IR source has significant utility in a wide array of applications including sensing and combustion diagnostics.
In the present report we discuss new physical principles for creating super-high-energy pulsed HF lasers and amplifiers based on a photon-branched chain reaction (PBCR). In the proposed mechanism, no external energy is consumed. We also formulate the demands for constructing lasers of this type. It is shown that a multi-pass optical scheme of a pulsed chemical HF laser allows for the initiation of an auto-wave PBCR by external radiation. Self-supporting cylindrical zones of photon branching sequentially initiated by multiple reflections by the mirrors of an unstable telescopic cavity. Such cylindrical zones of photon branching can be considered as amplifying cascades enclosed by each other. The energy emitted by each subsequent amplifying cascade considerably exceeds the energy of the previous cascade, and the number of such cascades is determined by the cavity parameters: the diameters of the mirrors, the radius of curvature of the mirrors and the diameter of the input hole for the master oscillator. Thus, this multi-pass optical scheme allows for an effective scaling of the laser output energy up to extreme high values, even for a rather small working volume of the laser. We have conducted a parametrical study of the main laser units and we offer a specific design for a self-contained pulsed HF laser with multi-mega-joule output energy in a pulse. Also, a brief historical review of chemical lasers and the idea of a PBCR is presented in this report.
Based on laser kinetics and diffraction theories of resonators, the gas mixtures (CO2, N2, He, Xe and H2) and the resonator parameters of a typical sealed-off CO2 laser are optimized by applying a genetic algorithm for obtaining a maximal laser output power. With the optimized parameters, the simulated and measured laser power is 2.27 and 1.6 times greater than the usually non-optimized CO2 laser, respectively.
Excimer lasers are nowadays well established UV laser sources for the wide area of micromachining. Their high energy and average power at short UV wavelengths makes them ideal for ablation of various materials e. g. polyamide and PMMA. The typical excimer laser sources used in micro machining deliver several hundred mJ of energy at repetition rates of up to 400 Hz. In parallel to this high-energy-micromachining an alternative excimer based method came up during the last years. This new technology is driven by the ever shrinking feature sizes of microelectronic circuits and utilises UV wavelength resist exposure. The resist exposure technology offers new possibilities also for micromachining. It is ideal for micro applications which require high precision patterning - with a positional accuracy of below 50 microns - at high volume throughput. In this process the laser energy dose may be built up in several shots, UV lasers with several hundred mJ cannot be utilised. Hence, high repetition rate lasers are needed.
In this paper the basic feature and performance characteristics of the new laser will be presented.
In the present report a novel diffractive technique for effective optical pumping of power chemical lasers by external coherent radiation is proposed. This technique utilizes a bicomponent diffraction system coupled structurally to the unstable telescopic cavity of the laser. The space localization of the electromagnetic field inside the proposed optical scheme represents a periodic structure of diffractive maxima in the near field-zone and a narrow paraxial diffraction channel with high intensity in the far-field zone. In the Fresnel diffraction zone, the optical effect of multifocal diffractive focusing of the radiation is observed. Here the intensity in the central peaks can exceed by a factor of six (for spherical waves) to ten (for plane waves) the value of the incident wave intensity. The diffractive focusing of the input radiation opens the possibility to create a narrow diffraction initiation channel inside the laser cavity with a given space distribution and a high intensity. This technique provides a high efficiency for optical pumping and makes it possible to get a huge value of the laser energy gain. Calculations show that the ignition of laser-chemical reactions in the diffraction initiation channel under the condition of diffractive focusing of input radiation allows the laser energy to reach a gain of up to 109.
Amplitude-temporal and spectral parameters of laser radiation and electric discharge parameters in gas mixtures of SF6 with hydrogen and hydrocarbons are studied. Experimental conditions providing high intrinsic efficiency of a non-chain HF laser are determined. The laser efficiency with respect to deposited energy up to ηin ~ 10% is obtained using discharge excitation by inductive and capacitor generators in SF6-H2 mixtures. High discharge uniformity obtained with the use of special shaped electrodes along with uniform UNV preionization is key parameter for improving intrinsic efficiency of discharge HF-laser. There with output spectra of the HF laser significantly widens and cascade laser action on some rotational lines of the vibrational transitions of HF molecules v(3-2) → v(2-1) → v(1-0) is observed. Specific output of the non-chain HF-laser over 8 J/l (140 J/lxatm) and total laser efficiency η0~4,5% were achieved, as well.
The possible construction of a self-contained and compact pulsed chemical HF-laser based on an auto-wave photon-branched chain reaction initiated in a gaseous disperse medium composed of H2-F2-O2-He and Al particles by focused external IR radiation is studied theoretically. It is shown that minimization of the parameters of the main pulsed HF-laser units are achievable due to both the effect of ignition of the laser-chemical reaction in an auto-wave regime under the condition of external beam focusing and the effect of a huge laser energy gain of 1011. These effects provide strong reduction of the input pulse energy necessary for initiation, down to ~10-8 J, and make it possible to construct a self-contained laser with kilojoule output energy per pulse, which can be initiated by a small sub-microjoule master oscillator powered by an accumulator. Due to an increase in the general pressure of the working gases, up to P = 2.3 bar, and optimization of the parameters of the dispersed component (Al particles with a radius of r0 = 0.09 μm and a concentration of N0 = 1.4×109 cm-3), and the composition of the working mixture, the HF-laser system will ensure an output energy up to ~ 1.5 kJ in a pulse, produced in a small volume of ~ 2 L of active medium.
A huge energy gain is predicted theoretically in a pulsed chemical laser-amplifier based on a photon-branched chain reaction initiated in a gaseous dispersed medium composed of H2-F2-O2-He and Al particles by focused external infrared radiation. It is shown that this effect is due to the possibility of ignition of the laser-chemical reaction in an initial small focal volume of the active medium. It then spreads out of this minimal volume spontaneously in the auto-wave regime without external power sources and subsequently fills the entire volume of the laser cavity with a high intensive electromagnetic field as self-supporting cylindrical photon-branching zones formed by the paths of the rays inside the unstable telescopic cavity. Calculations show that the ignition of an auto-wave photon-branched chain reaction under the condition of external signal focusing reduces strongly the input pulse energy necessary for initiation up to ~ 10-8 J, and thereby allows a huge value of the energy gain of ~ 1011. The predicted effect of this huge laser energy gain should make it possible to construct a self-contained laser, which can be initiated by a very weak source signal.
By means of a microwave generator chlorine diluted by helium was dissociated to chlorine atoms that subsequently reacted with hydrogen azide to produce the excited states of NCl(a1Δ). Meanwhile, molecular iodine with carrier gas of helium reacted with atomic chloride to produce atomic iodine which then was pumped to excited state of I(2P1/2) by an energy transfer reaction from NCl(a1Δ). In this paper, the changes of NCl(a1Δ) and NCl(b1Σ) emission intensity is presented upon admitting I2/He into the stream of Cl/Cl2/He/HN3/NCl(a1Δ)/NCl(b1Σ). Moreover, the production of excited state of atomic iodine I(2P1/2) dependent on flow rates of gases was also investigated. The optimum parameters for I(2P1/2) production are given.