A continuously variable attenuator for the CO2 laser

A continuously variable attenuator for the CO₂ laser, causing minimal degradation of beam quality, is implemented using rotating ZnSe wedges, and is capable of transmissivities between 0.3% and 18%, and between 27% and 89%. The transmissivity at any particular setting was measured to be essentially constant for wavelengths from 9.27 μm (9R20) to 10.77 μm (10P36).     

Variation of the gas components of a TEA CO2 laser during its lifetime

An in situ mass-spectrometric sampling technique has been developed for lifetime studies of TEA CO₂ lasers. Using the new technique, an analysis of the gas components of a TEA CO₂ laser during its lifetime has been performed. The results show that the laser output pulse energy was strongly influenced by the oxygen concentration inside the device.     

Pulse behaviour of a compact RF discharged CO2 slab laser

We present the measurements made on a medium power, 35 cm long, radio-frequency discharge CO₂ slab laser operated in a pulsed regime obtained by switching the RF discharge. In this way, pulses with peak power up to 480 W at pulse repetition frequencies in the range 1 to 10 kHz have been obtained. Pulse energy and average extracted power have been experimentally characterized with respect to the pulse repetition frequency and to the pulse duration, and the pulse shape and characteristic times have been measured. We also investigated the propagation properties of the beam emerging from our laser.     

Absorption coefficients of O3 at CO2 laser wavelengths

The O₃ absorption coefficients for the rotational lines P(12)–P(28) of the 9.4 μm emission band of the CO₂ laser are presented. Measurements were made in O₃–air dilute mixtures (20–600 ppm) at 25°C and a total pressure of 1013.25 h Pa using a frequency stabilized cw CO₂ laser and values have been determined with greater precision than in previously reported studies.     

Advanced CO2 laser rangefinders

Factors affecting the design of compact heterodyne- and direct-detection systems are contrasted. Recent UK achievements are placed in context: a TEA laser direct-detection rangefinder and a chirp-pulse-comparison rangefinder-velocimeter are described.     

CO2/H2O混合气体在水平管外凝结换热与分离特性研究

本文通过实验研究了CO₂质量分数为11.39%~70.95%,壁面过冷度为5~25 K,总压力为5~15 kPa的CO₂/H₂O混合气体自然对流条件下在水平管外的凝结换热规律,结果表明CO₂/H₂O的凝结换热系数随CO₂含量和壁面过冷度的增大而降低,但随总压力的增大而增大。根据实验结果建立了新关联式,将关联式应用到凝汽器的设计计算与分析,且对凝汽器进行了分离特性和经济性分析。     

Radiofrequency spectroscopy of AsH3 inside a CO2N2O laser cavity

The method of radiofrequency spectroscopy inside a CO₂N₂O laser cavity has been applied to the observation of pure nuclear quadrupole resonance, A₁-A₂ transitions and two-photon transitions of AsH₃. From the assignment of these transitions some coincidences between laser lines and Δk = 3 transitions in the ν₂ band and Δ|k ? l|; = 3 transitions in the ν₄ band have been assigned. The quadrupole coupling constant eqQ and its rotational dependence χ_J, χ_K and χ_d, and the spin-rotation constants C_N and C_K for the As nucleus have been determined for the ground state. The effective values of eqQ has been determined for the ν₂ and the ν₄ states.     

Current CO2 laser surgery

With the development of suitable instrumentation, human-engineered to fulfil the requirements of the clinical surgeon and designed to fit in with the physical conditions prevailing in the operating theatre, laser surgery has advanced rapidly in the past few years. It shows signs of even more rapid progress and general acceptance as its application and advantages in more and more fields of surgery are demonstrated.     

A gigahertz tunable, high power, high repetition rate rf CO2 laser operating without He

This paper reports on a gigahertz mode-tunable waveguide CO₂ laser operating with high-pressure He-free mixtures (0.4 bar), with a long pulse (20 μs) high repetition rate (1 kHz) radio-frequency discharge. Single-mode tuning at 0.92 GHz with good mean laser linewidth (<40 MHz) and large peak power (150 W) have been obtained over 40 laser lines, with 0.3 W mean power. By using standard He reach mixtures both the laser line number and mean power are slightly increased.     

A new design for a high-power, tail-free high repetition frequency single-mode CO2 laser

A new discharge design for pulsed CO2 lasers has been made with a series of short longitudinal synchronous discharges working at high pressure with large section. In this way, single-mode high-power (up to 40 kW at 100 ns) tail-free pulses have been obtained at intermediate repetition frequency (25 Hz) in a He-free mixture dominated by CO₂ (75–90% content). This laser is ideal for producing frequency mixing in non-linear crystals.     

O2/CO2气氛下循环流化床煤燃烧SO2排放

在热输入功率50 kW的循环流化床O₂/CO₂燃烧试验装置上研究燃煤SO₂排放特性及石灰石脱硫机理。结果发现,未添加石灰石时,O₂/CO₂气氛下SO₂排放量比相同O₂浓度的空气气氛下低;随着O₂浓度的升高,排放量升高。相同钙硫摩尔比下,O₂/CO₂气氛下石灰石的脱硫机理以直接脱硫为主,脱硫效率比空气气氛下高;随着O₂浓度的增加,石灰石脱硫效率提高。     

O2/CO2气氛下CO对煤焦异相还原NO影响的研究

为揭示O₂/CO₂燃烧过程中高浓度的CO对煤焦异相还原NO的影响,在1073 K温度下使用山西褐煤在卧式炉上进行了实验。分别对O₂/CO₂浓度比及CO浓度下NO的还原特性进行详细实验研究。研究结果表明:在O₂/CO₂气氛下,O₂浓度为30%时具有较高的还原率;相同O₂浓度下O₂/CO₂气氛较空气气氛NO还原率高,表明在CO存在的条件下,高浓度的CO₂会促进NO的还原;当CO浓度从1.5%逐渐升高时,NO的还原率逐渐降低,到CO浓度为5%时,NO还原率比没有加入CO时还要低,而在空气气氛下CO浓度的变化对NO的还原率影响较小。     

Various techniques for multiline operation of TEA CO2 lasers

The various techniques used for multiline operation of TEA CO₂ lasers are reviewed with particular reference to the multiline laser parameters of interest in laser applications.     

CO2 laser welding of copper slabs

For the first time it has been possible to laser weld copper sheets up to 3 mm thick with a 2 kW cw CO₂ laser. The main questions arising from the process are indicated.     

CO2 laser cutting of slate

Slate is a natural stone which has the characteristic that shows a well-developed defoliation plane, allowing to easily split it in plates parallel to that plane which are particularly used as tiles for roof building. At present, the manufacturing of slate is mostly manual, being noisy, powdery and unsafe for the worker. Thus, there is a need to introduce new processing methods in order to improve both the working conditions and the quality of the products made of slate.Following the previous work focused on the drilling and cutting of slate tiles using a Nd : YAG laser, we present in this paper the results of the work carried out to explore the possibilities to cut slate plates by using a CO₂ laser. A 1.5 kW CO₂ laser was used to perform different experiments in which, the influence of some processing parameters (average power, assist gas pressure) on the geometry and quality of the cut was studied. The results obtained show that the CO₂ laser is a feasible tool for a successful cutting of slate.     

N_2O的近红外腔增强吸收光谱技术研究

以外腔式可调谐、窄线宽近红外半导体激光为光源,以一对曲率半径r=1 000mm的宽带高反射率平凹镜(反射率R=99.97%)构成的腔长为650mm的对称高精度光学稳定腔,建立了腔增强吸收光谱系统。详细研究了纯净N2O气体、以及N2O和N2的混合气体在不同浓度和不同气压下、中心波长位于6 561.39cm-1的腔增强吸收光谱、光谱强度和谱线宽度,该腔增强吸收光谱系统的有效吸收光程可达1 460km。获得了光谱线宽与气体压强的关系曲线,导出了波数6 561.39cm-1处N2对N2O的压力展宽系数为(0.114±0.004)cm-1·atm-1。采用该腔增强吸收光谱系统,开展了N2O气体检测研究,建立可用于定量检测的N2O气体腔增强吸收光谱强度与气体浓度关系曲线,获得了2.34×10-7cm-1的检测灵敏度,多次重复测量的相对标准偏差(RSD)为1.73%,在微量N2O气体检测中具有很好的应用前景。     

Reconstructive microsurgery of the female reproductive tract using a CO2 laser

Laser tubal microsurgery was carried out on a sample of 82 patients. Employing current laser surgical systems, 21 conceptions occured in 20 patients, after limited exposure to conception risk during the 13-month study. This represents 48% of the 42 patients at risk. Tubal patency was demonstrated in 94% of the 82 cases. Based upon experience to date, more conceptions are expected as more patients become at risk and as exposure increases.     

N_2O的离轴腔增强吸收光谱检测技术

基于离轴腔增强光谱检测技术,以可调谐近红外半导体激光器作激光光源,以反射率为99.97%平凹镜组成的光学谐振腔作吸收池,建立了高灵敏度离轴腔增强光谱污染气体检测系统,获得了N2O气体在6 561.39cm-1的吸收光谱.通过对不同浓度N2O样品气体吸收光谱测量,建立了气体浓度与光谱线强度的关系,讨论了气体压强与光谱线宽、检测灵敏度等问题.研究结果表明,离轴腔增强光谱检测技术的检测极限达到了86ppm,是一种设备成本低、操作方便、灵敏度较高、稳定性良好的吸收光谱技术,可以很好地实现微量气体的快速检测.     

Far-infrared hydrazine laser pumped by an N2O laser

We have used an N₂O laser to optically pump N₂H₄ molecules in a far-infrared cavity and observed 17 new laser lines in the wavelength range 93.0 to 374.2 μm, the 136.8 μm line pumped by 10P(16) being a doublet. We measured the frequencies of the laser lines by heterodyne mixing of the far-infrared radiation with radiation from two frequency-stabilized CO₂ lasers.     

Mathematical modelling of gain-switched RF-excited CO2 waveguide laser

The detailed mathematical models for the evolution of light pulses in RF-excited CO2 waveguide lasers are derived. Explicit expressions for the pulse characteristics in RF-excited CO2 waveguide lasers are obtained. The effects of losses and unsaturated gain on output power are calculated.