激光分离卵磷脂混合物的实验研究

对于沸点相近并且分子自由程相差不大的物质,常规分离方法难以实现有效的分离,激光分离有效地弥补了常规分离方法的不足.用脉冲CO2激光器和连续CO2激光器对大豆卵磷脂混合物进行了激光分离实验,用高效液相色谱对激光辐照前后的样品进行了分析.经192.31 W/cm2的脉冲CO2激光辐照,卵磷脂的质量分数相对提高了26.7%,...     

Output couplers of ultra-transparent KCl and NaCl in a pulsed CO2 laser

Uncoated plane parallel windows made from ultra-transparent KCl and NaCl crystals, which were grown by ‘injecting the reactive atmosphere’ (IRA) technique, have been tested as output windows in a high-power, high-repetition TEA CO₂ laser, in various resonator configurations. Output power densities per pulse of 2 to 6 MW cm^-2, which are 40% to 60% less than with 50% reflective coated ZnSe, have normally been obtained. The laser performances did not change after one year of operation and more than 10⁷ pulses per window. No laser damage has been observed.     

Operation of an unstable resonator TE CO2 laser with large electrode spacing using additives

A study of a pulsed transversely excited (TE) CO₂ laser using an unstable resonator configuration is reported. It is shown that a large aperture (4.75 cm) wire-triggered device can successfully operate at pressures of up to 650 torr with undoped gas mixtures whose molecular gas concentration exceeds 35%. These results are utilised for a comparative study of the influence of an organic additive on the performance of the system. It is observed that the addition of traces of tri-n-propylamine leads to significant improvements of the laser output characteristics even under conditions where a glow discharge could be obtained without the additive. With the doped TE CO₂ laser employed using a relatively low magnification unstable resonator (M = 1.45) near diffraction-limited performance has been achieved and a peak radiance of 4.5 × 10¹³ W cm⁻² sr⁻¹ has been obtained with a peak power of 65 MW.     

Properties of a laser beam generated from an axicon resonator

A high power cw CO₂ laser beam is generated from a resonator configuration having an axicon mirror as its end reflector. The properties of this beam are evaluated in terms of its polarization, focusing capability and temporal stability and the resulting effects on processing materials are presented. A comparison is made between a folded and a straight resonator having a spherical focusing mirror as its end reflector.     

Cutting and welding using a CO2 laser

Of all the types of lasers now available, the CO₂ laser is particularly suitable for materials working. It has a very high efficiency (15–20%) and a high out-put power (up to several kW). When the laser light is focused by means of a lens or a mirror, a c.w. power density of more than 10⁹ W cm^-2 can be attained. The laser need not be used in vacuum.

The CO₂ laser is a suitable cutting tool for numerous materials. These include metals such as titanium or steel; combustible materials such as paper, textiles and wood; and plastics. The CO₂ laser can also cut hard and brittle materials such as aluminum oxide and silicon carbide. If metals are cut in an oxidizing atmosphere, the cutting speed may be increased. The cutting width, however, is determined by the size of the laser spot. Another important field of application is the growth of single crystals.

Experiments are reported in which the CO₂ laser was used for welding steel, titanium, plastics, quartz, and glass. The advantages of the laser for this application are discussed. A comparative study of laser and electron beam techniques is included.     

An unstable confocal resonator with unitized output coupling

The structure and the output characteristics of an unstable confocal resonator with unitized output coupling were studied in detail. The output power, the electrical-photo conversion efficiency and far-field intensity distribution of high-power transverse flow cw CO₂ laser with unitized output coupling unstable resonator (the geometrical magnification parameter M is equal to 1.5) have been measured. The output power is larger than 1.8 kW; the electrical-photo conversion efficiency is as high as 14% and the far-field divergency (total angle) is about 2 mrad. Control experiments show that under otherwise equal conditions the output power and the efficiency of an unstable resonator with scraper plate coupling are 1.2 kW and 9.2%, respectively.     

Configuration analysis of the resonator in a double-pulse TEA CO2 laser

This paper describes the resonator configuration of a double-pulse TEA CO₂ laser, and discusses how to obtain single-mode operation in that configuration.     

Development of a high power gas transport CO2 laser with with cylindrical geometry

The aim of this work is to report the achievement of a light weight, compact, high power CO₂ laser which can be used in industry. The construction and operation of a CO₂ gas transport laser with cylindrical geometry and two parallel electrical discharges are presented. Using a 600 mm diameter, 1400 mm length, 250 kg laser head, we have obtained more than 1.6 kW laser power with 2% stability and 2 mrad full angle divergence. For comparison the results are presented for one electrical discharge laser.     

基于匹配算法的脉冲差分吸收CO2激光雷达的稳频研究

利用差分吸收激光雷达探测大气CO₂, 可以获得其浓度的垂直分布, 对于研究碳源、碳汇的过程有重要意义. 设计了一套种子注入的脉冲差频激光器系统, 作为差分吸收激光雷达的激光光源. 针对脉冲差分吸收CO₂激光雷达on波长的高精度稳频的研究空白, 本文提出一种基于匹配的on波长的连续稳频算法. 其基本思想是采用分子饱和吸收法, 测量通过双路吸收池后的差分信号, 计算其光学厚度值(optical depth, OD), 获得实测的伪吸收谱, 当监测到on波长发漂移后, 进行连续的波长调节, 获取其OD值, 最后基于一维的图像匹配算法, 将OD值作为灰度值, 利用图像匹配原理, 进行OD值匹配, 确定当前输出波长在伪吸收谱中的位置, 进而调节至on波长, 实现on波长的连续、稳定输出. 实验结果表明, 提出的稳频算法能够很好的满足高精度的稳频要求, 同时差平方和法在该应用中是最优的, 稳频精度可达到0.3 pm.     

Studies on CO2 laser marking

The nature of CO₂ laser marking was studied with a view to putting these lasers to practical use in the semiconductor industry. The marking is found to be due to surface spattering rather than burning, which is the main factor in YAG laser marking. The visibility greatly increases by the application of a surface treatment such as marker ink, varnish or poster color. The CO₂ laser may therefore be used in place of the YAG laser, now widely used for marking, with some merits: CO₂ laser marking is cheaper and faster, and in addition there is no danger of injury from irradiating laser light.     

轴对称折叠组合腔CO2激光器的实验研究

对轴对称折叠组合腔CO2激光器进行了相关的实验研究。主要用线图的方式研究了在两种不同混合气体比例条件下,输出功率与放电电流之间和输出功率与放电气压之间的关系。引入辅助气体xe后,输出功率有很大的提高,能够达到35％左右。根据模型结构的实际参数,运用数值计算的方法模拟画出其输出光强和光斑分布图。以三维5根、7根和9根放电...     

Efficient doubling and CW difference frequency mixing in the infrared using the chalcopyrite CdGeAs2

We have obtained fifteen percent average internal power conversion efficiency for second harmonic generation in CdGeAs₂ of radiation from a TEA CO₂ laser operating at 10.6 μm. This is the highest reported doubling efficiency for a CO₂ laser. We have also observed cw difference frequency mixing in CdGeAs₂ at wavelengths between 11.4 and 16.8 μm using grating-tuned CO and CO₂ lasers. The CdGeAs₂ crystals are significantly improved in size and optical quality over those previously available.     

新型燃煤发电-CO2捕获-供热一体化系统

本文在深入分析燃煤电站CO₂捕获和汽水系统热平衡的基础上,提出一种新型燃煤发电-CO₂捕获-供热一体化系统。该系统通过汽水流程、碳捕获流程及地暖供热流程的有效集成,实现了系统中、低温余热的高效利用,降低了碳捕获对电厂效率的影响。分析结果显示,本文提出的一体化系统,在CO₂回收率90%时,供电效率可达31.32%,供电效率降低8.96%,而传统化学吸收法碳捕获电站效率惩罚普遍在10～12个百分点或更高。同时,该系统可供热350 MW,全厂（火用）效率达34.49%,全厂热效率高达55.88%;该系统以较少的能耗代价实现高效供电、供热与CO₂减排,为燃煤发电机组碳减排提供了独特的学术思路与技术方案。     

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。     

Phase-locking of axisymmetrical-fold combination CO2 laser

Two new methods for phase-locking are used in the axisymmetrical-fold combination CO₂ laser. We demonstrate the feasibility of two methods by theoretical deduction, and give the light intensity distribution of far field by numerical simulation. When phase is locked, the axisymmetrical-fold combination CO₂ laser can provide a high output power with good beam quality. Furthermore, the peak light intensity of output beam with phase-locking is obviously higher than that without phase-locking.     

Characterization and frequency measurement of a new far infrared laser line from CHin2Fin2

We present the discovery and frequency measurement of a new FIR laser line from CH₂F₂ optically pumped by a waveguide CO₂ laser. This new line has the same CO₂ laser pump line (9R32), offset (+5 MHz) and relative polarization of the strongest FIR laser line of CH₂F₂, namely the 184.3μm. The frequency is only 19,454 MHz apart from that of this line. We got a frequency measurement of 1,646,196.6 (10) MHz, which corresponds to a wavelength of 182.112 μm.     

Photo-operated two-photon absorption effects in the GeSe2–Ga2S3–PbI2 glasses

The possibility to operate the two-photon absorption (TPA) of newly synthesized GeSe₂–Ga₂S₃–PbI₂ glasses using the CO laser beam (λ=5.5 μm) as a photoinducing one has been demonstrated. As the fundamental laser beam we have used the illumination of 10.6 μm passively modulated 0.5 ns CO₂ laser with a rate repetition of about 10 Hz. We have established that the maximal photoinduced TPA is observed for the 8% doped samples (up to 14 cm/GW), which is achieved at a pump CO laser pump power density equal to about 0.6 GW/cm². The undoped PbI₂ samples show the TPA maximum at a pump power density of about 0.2 cm/GW. The minimal TPA values were observed for the samples with 5% of PbI₂. The obtained results show that these materials can be used as effective optically operated optical limiters.     

Numerical calculation of the use of a concave–convex lens for shaping axisymmetric laser beams

Based on transformation matrices in meridian plane and sagittal plane, a geometrical lens design method is presented with the aim of obtaining an improved spot. A concave–convex convergent lens (CCCL) is employed as a shaping lens to focus a group of oblique laser beams from a CO₂ laser with axially symmetrical fold combination (ASFC) resonator. The cases including interference, noninterference, different wavelength, and misalignment have been analyzed. Through theoretical analysis and numerical calculation, a smaller beam radius in a specific reference plane and a smaller far-field divergence angle can be obtained.     

A study of laser cutting engineering ceramics

A mechanical chopper Q-switched CO₂ pulse laser with high peak power, short pulse duration, high pulse repetition rate and moderate average power is developed. Using this laser, a multi-pass cutting process with high cutting speed is proposed for cutting hard and brittle materials such as engineering ceramics. Crack-free and fine cut is obtained in cutting Si₃N₄ ceramics. Moreover, the formation and elimination of the cracks are qualitatively analyzed in the paper.     

Fine frequency tuning of a high power CO2 laser and its application to optically-pumped molecular lasers

We describe a novel technique for shifting the output frequency of a high power TEA CO₂ laser. The performance of a 16 μm laser is shown to be greatly improved when optically pumped by this tunable source.