A 2-kW COIL with a square pipe-array JSOG and nitrogen buffer gas

A 2-kW-class chemical oxygen-iodine laser (COIL) using nitrogen buffer gas has been developed and tested since industrial applications of COIL devices will require the use of nitrogen as the buffer gas. The laser, with a gain length of 11.7 cm, is energized by a square pipe-array jet-type singlet oxygen generator (SPJSOG) and employs a nozzle bank with a designed Mach number of 2.5. The SPJSOG has advantages over the traditional plate-type JSOG in that it has less requirements on basic hydrogen peroxide (BHP) pump, and more important, it has much better operational stability. The SPJSOG without a cold trap and a gas-liquid separator could provide reliable operations for a total gas flow rate up to 450 mmol/s and with a low liquid driving pressure of around 0.7 atm or even lower. The nozzle bank was specially designed for a COIL using nitrogen as the buffer gas. The cavity was designed for a Mach number of 2.5, in order to provide a gas speed and static temperature in the cavity similar to that for a traditional COIL with helium buffer gas and a Mach 2 nozzle. An output power of 2.6 kW was obtained for a chlorine flow rate of 140 mmol/s, corresponding to a chemical efficiency of 20.4%. When the chlorine flow rate was reduced to 115 mmol/s, a higher chemical efficiency of 22.7% was attained. Measurements showed that the SPJSOG during normal operation could provide a singlet oxygen yield Y/spl ges/55%, a chlorine utilization U/spl ges/85%, and a relative water vapor concentration w=[H/sub 2/O]/([O/sub 2/]+[Cl/sub 2/])/spl les/0.1.     

Parametric study of an efficient supersonic chemical oxygen-iodinelaser/jet generator system operating without buffer gas

A detailed experimental study of an efficient supersonic chemical oxygen-iodine laser is presented. The laser is energized by a jet-type singlet oxygen generator, operated without primary buffer gas and applies simple nozzle geometry and transonic mixing of iodine and oxygen. Output power of 190 W with chemical efficiency of 18% was obtained in a 5-cm gain length for Cl₂ flow rate of 11.8 mmole/s. The power is studied as a function of the distance between the optical axis and the supersonic nozzle exit plane, the molar flow rates of various reagents, the basic hydrogen peroxide solution and gas pressures in the generator, the type of the secondary buffer gas (N₂ or He) and the stagnation temperature of the gas. It is found that the power under the present operation conditions is almost unaffected by water vapor in the medium. The role of buffer gas under different conditions is discussed     

电激励氧碘激光器研究最新进展

氧碘激光是由激发态O2(1△)与基态碘原子近共振传能来实现的.传统的氧碘化学激光器(COIL)采用气液化学反应来产生O2(1△).一种全气相、更安全易行的基于电激励O2(1△)发生器的氧碘激光器是当前国际上的研究热点.通过对最新文献的综述分析,归纳整理了电激励氧碘激光器(EOIL)研究中的关键问题所在,并对未来发展趋势及需要解决的问题等进行了分析总结.     

化学氧碘激光器（COIL）的研究进展

化学氧碘激光器（COIL）作为继HF／DF化学激光器以后的第二代气流化学激光器具有诸多优点,如比第一代更短的波长和更高的光纤传输效率,因而在军事、工业和医疗等许多领域都有重要的应用,在过去的十多年来得到了各国专家的普遍重视。本文将对化学氧碘激光器几十年的发展进行一定回顾和分析,并在此基础上对其未来的发展和所面临的技术挑战进行了探讨。     

High-performance chemical oxygen-iodine laser using nitrogendiluent for commercial applications

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     

光引发脉冲氧碘化学激光器的研究

研究以O_2(~1⊿)-RI-N_2作为反应混合物的光引发脉冲氧碘化学激光,其激光能量输出高于160mJ,O_2(~1⊿)能量利用效率为12％。对O_2(~1⊿)-CH_3I-N_2和O_2(~1⊿)-CF_3I-N_2体系作了比较,以前者为佳。试验也证实以N_2代替Ar作为缓冲气,可得到同样高的激光输出。     

脉冲氧碘化学激光放大器的理论模型

本文提出脉冲氧碘化学激光主振荡器加功率放大器(MOPA)系统中放大器的理论模型。计算表明:氧碘放大器内采用折迭光路方案,可以获得高的放大率及化学效率。     

Power optimization of small-scale chemical oxygen-iodine laser withjet-type singlet oxygen generator

Studies of power optimization of a 5-cm gain length chemical oxygen-iodine laser (COIL) energized by a jet-type singlet oxygen generator (JSOG) are presented. For 10 mmol/s of Cl₂ flow rate, output power of 132 W with chemical efficiency of 14.5% was obtained without a water vapor trap, 163 W and 18% were achieved when coholed (173 K). He was introduced downstream of the JSOG; under these conditions, the small-signal gain was estimated to be 0.32% cm^-1 . 190 W and 10.5% were obtained for 20 mmol/s of CI₂ flow rate. Replacing He by N₂ as a buffer gas resulted in a 13% power decrease only. The main key for increasing the chemical efficiency of a COIL without a water vapor trap for a given iodine-oxygen mixing system is found to be high oxygen pressure and low water vapor pressure inside the reaction zone of the JSOG. The last goal was achieved by optimizing the composition and temperature of the basic hydrogen-peroxide solution (BHP). The experimental results are discussed and related to the composition and flow conditions of the gaseous reactants and of the BHP     

面阵滑闪火花预电离放电引发脉冲氧碘化学激光的实验研究

采用脉冲气体放电可以实现连续波氧碘化学激光器的脉冲化输出来获得高峰值功率。提出了面阵滑闪火花预电离电极结构并解决了大体积辉光放电问题。将这个电极结构应用到脉冲氧碘激光器中,获得了单脉冲能量为4.4 J,脉宽为58 s,峰值功率为75 kW的脉冲激光。脉冲峰值功率与连续波平均功率之比为63。研究了发生器的P和输出耦合镜透射率对激光特性的影响。     

Characterization and Studies on Hydro Dynamically Stable Operation of an Angular Jet SOG for COIL

Chemical oxygen-iodine Laser (COIL) is one of the fast emerging high power laser source for near Infrared (λ=1.315μm) laser generation. The heart of the system is the singlet oxygen generator (SOG) which is a pumping source for this laser. A Jet type SOG with a novel approach was designed and fabricated. Singlet oxygen was 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 preliminary results have been reported in our earlier publication. The present paper discusses the performance of this generator for various operational conditions viz. diluent's gas nitrogen / helium, basic hydrogen peroxide composition, generator pressure and gas velocity. Further, conditions for the stable operation from generator as well as chlorine injection point of view have been identified.     

Chemical oxygen-iodine laser using a new method of atomic iodine generation

The chemical oxygen-iodine laser (COIL) with a new chemical method of atomic iodine production was investigated. In this system, iodine atoms are formed in the COIL cavity by the fast chemical reaction of hydrogen iodide with chlorine atoms that are also produced chemically. It was found that, in the absence of singlet oxygen, the ground state atomic iodine can be produced with a high yield (80%-100%). In gas containing singlet oxygen, a gain on 3-4 electronic transition in iodine atom was achieved (0.35% cm/sup -1/). Both the concentration of atomic iodine and the gain depend substantially on the ratio of reacting gases and the penetration of secondary gases into the primary gas flow. In laser experiments, effects of the flow rate of reacting gases and their penetration on the laser output power were found. The output power of 310 W was attained at chlorine flow rate of 27 mmol/spl middot/s/sup -1/ corresponding to chemical efficiency of 12.7%. This was the first time the gain and laser output power were achieved in the COIL with atomic iodine generated by the proposed method.     

脉冲氧碘化学激光模型

采用闪光灯光解RI得到碘原子,再与电子激发态氧O_2(~⊿)传能产生脉冲碘激光的模型。此模型包括35个化学动力学过程。采用Runge-Kutta-Gill积分法求解,得到的结果表明脉冲氧碘化学激光器具有高的效率,提高激光器性能的关键在提高O_2(~1⊿)的分压。     

激光辐照皮肤组织的热效应解析计算研究

为了研究工作波段在近红外的激光安全问题,建立了连续激光辐照生物组织的热学模型,通过分离变量法求解热传导方程,得出了生物组织在激光辐照阶段和扩散阶段皮肤组织瞬态温度分布的精确解析解,并以氧碘激光辐照皮肤组织为例,计算了皮肤组织在激光辐照下的温度场分布。结果表明,皮肤组织温升随激光辐照时间和功率密度的增加而增加,辐照结束后,皮肤表面温度缓慢下降,深处温度先缓慢上升,再缓慢下降。分析结论与相关实验结果取得一致,证实了所建模型的合理性。该结论对于其它连续激光对物质的热损伤研究是有帮助的。     

Application of a telescopic resonator to high-power chemicaloxygen-iodine lasers

The application of an intraresonator telescope to high-power chemical oxygen-iodine lasers to decrease the output beam divergence is analyzed and demonstrated. A theoretical formula based on the ABCD matrix theory is developed to analyze the characteristics of the telescopic resonator. Calculations are carried out using Galilean type telescopes with magnification factors in the range of two to four, and our high-power chemical oxygen-iodine laser as an analysis model. By locating the telescope at a proper position on the optical axis, the overall telescopic resonator can be conveniently tailored to the hardware of this model laser in a way that the beam divergence and the resonator stability can be improved simultaneously. Experiments are carried out for one of the conditions used in the calculations. Measured divergence angles are in excellent agreement with the theoretical values     

氧 碘化学激光辐照纯铝的温度场数值模拟

氧碘化学激光(COIL)(波长1.315μm)辐照纯铝表面,激光束斑直径为6 mm,功率密度为10～20 kw/cm2,材料表面在激光能量作用下瞬间发生熔化.以傅里叶热传导模型为基础,利用ANSYS对化学激光与铝相互作用的过程进行模拟,得到了熔池的形貌特征及相关的温度时间关系曲线.对不同功率密度激光作用的模拟结果进行分析,并求解了纯铝熔化破坏的激光功率阈值.     

Parametric study of small-signal gain in a slit nozzle, supersonicchemical oxygen-iodine laser operating without primary buffer gas

A detailed experimental study of the gain and temperature in the cavity of a supersonic chemical oxygen-iodine laser (COIL) is carried out to find optimal values of the flow parameters corresponding to the maximum gain. It is found that high gain (>0.7%/cm) can be obtained in a COIL operating without primary buffer gas and, hence, having a high gas temperature (>250 K) in the cavity. The measurements are performed for slit nozzles with different numbers and positions of iodine injection holes. Using a diode laser-based diagnostic, the gain is studied as a function of the molar flow rates of various reagents, with optical axis position along and across the flow, and Mach number in the cavity. Maximum gain of 0.73%/cm is obtained at chlorine and secondary nitrogen flow rates of 15 mmole/s and 7 mmole/s, respectively, for a slit nozzle with transonic injection of iodine. The gain is found to be strongly inhomogeneous across the flow. For a slit nozzle with iodine injection in the diverging part of the nozzle, the values of the maximum gain are smaller than for nozzles with transonic injection. Opening a leak downstream of the cavity in order to decrease the Mach number and increase the cavity pressure results in a decrease of the gain and dissociation fraction. The gain is a nonmonotonic function of the iodine flow rate, whereas the temperature increases with increasing iodine flow. An analytical model is developed for calculating in slit nozzles the iodine dissociation fraction F and the number N of O₂ (¹Δ) molecules lost in the region of iodine dissociation per I₂ molecule     

The hyperfine gain spectrum, gain profile, and cavity temperaturein a supersonic COIL

The hyperfine gain spectrum of a chemical oxygen-iodine laser (COIL) is investigated experimentally. Six hyperfine lines are obtained in a COIL gain medium as well as an iodine absorption cell. Meanwhile, gain profiles and cavity temperatures are calculated     

Spatial distribution of the gain and temperature across the flow in a slit-nozzle supersonic chemical oxygen-iodine laser with transonic and supersonic schemes of iodine injection

Spatial distributions of the gain and temperature across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit-nozzle supersonic chemical oxygen-iodine laser as a function of the iodine and secondary nitrogen flow rate, jet penetration parameter, and gas pumping rate. The mixing efficiency for supersonic injection of iodine (/spl sim/0.85) is much larger than for transonic injection (/spl sim/0.5), the maximum values of the gain being /spl sim/0.65%/cm for both injection schemes. Measurements of the gain distribution as a function of the iodine molar flow rate nI/sub 2/ were carried out. For transonic injection, the optimal value of nI/sub 2/ at the now centerline is smaller than that at off axis locations. The temperature is distributed homogeneously across the flow, increasing only in the narrow boundary layers near the walls. Opening a leak downstream of the cavity in order to decrease the Mach number results in a much larger mixing efficiency (/spl sim/0.8) than for a closed leak.     

Spatial gain measurements in a chemical oxygen iodine laser (COIL)

The spatial distribution of small signal gain has been investigated on the RADICL device, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F=3→F=4 hyperfine levels of the (² P_1/2) to (²P_3/2) spin-orbit transition in atomic iodine was used as a small signal probe. A peak gain of 1.2%/cm was measured along the horizontal centerline of the single-slit, supersonic nozzle, which is about two times greater than measurements made on ReCOIL by Hager et al. (1988) and compares favorably with measurements made on the RotoCOIL device by Keating et al. (1990). Gain distribution was investigated under three I₂ flow conditions. Scans across the supersonic expansion indicate a gradient in gain distribution due to higher gas temperatures along the walls and mixing phenomena     

Effects of Buffer Gas on the Output of Optically Pumped NH3 Far-Infrared Cavity Laser

By solving the semi-classical density matrix equations and developing a buffer gas mechanism model, the effects of buffer gas on the output power of optically pumped NH₃ far-infrared cavity laser were calculated and verified by experiment. Our results showed that: the output power of NH₃ far-infrared laser could be increased when certain buffer gas was added into the laser medium, and there existed an optimum ratio of gases mixture and an optimum operating gas pressure which could make the output power of far-infrared laser reach maximum.