大功率TEA CO2激光器的电磁辐射测试及屏蔽方舱设计

为了抑制大功率TEA CO<,2>激光器对其他电子设备的电磁干扰,在测量并分析激光器的近场电磁辐射特性的基础上,设计了电磁屏蔽方舱并进行了实验验证.根据大功率TEA CO<,2>激光器的工作原理,分析了激光器工作过程中的主要电磁辐射源;结合电磁辐射理论与激光器的实际结构,确定了电磁辐射测试的主要部位为火花开关、主回路、...     

Compact high-power TEA N(2) laser

A modification is adopted in the conventional Blumlein excitation system for realizing a simple and compact TEA N(2) laser. Super-radiant laser pulses of approximately 1.0 MW peak power, approximately 0.6 ns duration, and approximately 1.0 mrad divergence have been achieved.     

Digital feedback stabilization of a single-axial-mode CO2 TEA laser

We have achieved long-term stability in producing high-power single-axial-mode CO2 laser pulses with a hybrid oscillator (TEA laser + low-pressure section) by using a novel digital feedback system that electronically adjusts cavity length.     

Evaluation of cutting quality of PMMA using CO2 lasers

Polymethyl methacrylate (PMMA) is a versatile thermoplastic that is well suited for engineering and many common applications. This article presents a study to evaluate the effect of the processing parameters (laser power and cutting velocity) under the quality of the cut of PMMA. A plan of experiments was established considering CO₂ laser cutting with prefixed processing parameters in plates of PMMA with 6 mm thickness. The objective was to evaluate the quality of the cut (surface roughness, dimensional precision and heat affected zone-HAZ) in linear and complex 2D cutting. The obtained results show that PMMA in complex 2D cutting presents dimension of HAZ between 0.12 to 0.37 mm, without burr and low surface roughness Ra?<?1 μm. The results present good repeatability.     

A TEA CO2 laser with a peak radiation power of 100 MW

A high-power pulse-periodic TEA CO₂ laser is used as a component of a long-range mobile differential absorption lidar. In order to reach the ultimate peak generation power, a system for laser excitation with a supply voltage of ±40 kV and efficient preionization was developed, allowing the laser to operate at high pressures of gas mixtures of various compositions. Energy, time, and spatial characteristics of laser radiation were studied. Laser pulses with an energy of >10 J and FWHM duration of ≈30 ns were obtained. The ultimate peak laser radiation power is 100 MW, and the maximum efficiency with respect to the discharge-consumed energy is 12.6%.     

Compact flowing gas system for CO(2) lasers

A miniature air-actuated vacuum pump has been utilized to effect gas flow at partial atmospheric pressures for waveguide CO(2) lasers. Implications are that flowing gas laser systems can be acceptable for many applications requiring miniaturization of components.     

Absolute calorimeter for measuring low-energy outputs from CO2 lasers

This paper describes the construction of a calibrated energy measuring device for pulsed CO(2) lasers of low output energy. An aluminium disk of low thermal capacity has been used for the detection of laser radiation. An Al(2)O(3) layer has been electrolytically deposited on the aluminium disks. It is used as a highly absorbing surface (> 95% for wavelengths between 8.5 and 11.0 microm), thus eliminating the need for calibration. The laser output energy is calculated from the measured increase of temperature of a calorimeter disk of known thermal capacity. Calculations and measurements have shown that this device is capable of measuring the energy of a single pulse of the order of 1 mJ, and in a set of 10 pulses even to 0.1 mJ, for pulses as short as 1 ps.     

Heat dissipation in high-power semiconductor lasers with heat pipe cooling system

This study focuses on the application of heat pipes in thermal management for high-power semiconductor lasers. The heat pipe cooling systems are used for heat dissipation in high-power semiconductor lasers. These systems are used instead of water cooling machines to realize a compact and lightweight laser module. The n-shaped heat pipe cooling system, which consists of eight 6 mm copper heat pipes with sintered powder wicks, can easily handle a heat load of up to 73 W from a single-laser unit. The fabricated U-shaped heat pipe cooling system, which consists of ten 12 mm copper heat pipes with sintered powder wicks, can easily handle a heat load of up to 300 W from five laser units. The optical power of the multi-laser module cooled by the U-shaped heat pipe cooling system reaches 210 W. These results indicate that high-power semiconductor lasers can be cooled using heat pipe cooling systems instead of water cooling machines.     

高功率TEA CO2激光器的双波长免调切换结构

为在一台激光器上切换输出10.6/9.3μm两种波长高能激光,采用输出镜镀膜选支方法获得了9.3μm单谱线输出,其脉冲能量与原10.6μm波长基本相当.设计出双波长密闭免调切换输出结构,利用有限元分析软件MSC.Patran/Nastran对该结构的切换移动平台组件进行了静力学、热应力及热力耦合分析,并基于Matlab...     

两路脉冲固体激光器的相干合成

提出了采用迈克尔逊干涉复合腔技术进行两路固体激光器相干合成的实验方案.该方案利用双光束干涉时的相干相长和相干相消特性,结合谐振腔自身的增益损耗原理来实现两激光器的被动式相干合成.理论分析了该技术的锁相机理,并在实验中实现了两路脉冲固体激光器的相位锁定,获得了单脉冲能量300 mJ的相干合成激光输出,合束效率约为80％....     

Gap-free lap welding of zinc-coated steel using pulsed CO2 laser

CO₂ laser welding of zinc-coated steel sheets in the lap configuration has been a major research effort for the automotive industry for many years. The introduction of a gap between the sheets is one way of solving the zinc gas explosion problem. However, this requires sophisticated clamping devices and spacer materials. A homogeneous gap is therefore difficult to realise in high volume production. This paper describes a simple but useful approach for CO₂ laser welding of zinc-coated steel sheets in the lap configuration. By using a gated pulse mode, a seam welding process is developed that allows zinc-coated materials to be welded in a gap-free, overlap configuration. Laser seam welds in the lap configuration were produced in 0.7 mm-thick steel sheet with 7 μm zinc coating on both sides. A number of pulsed CO₂ laser welding parameters, including peak power, duty cycle, travel speed, pulse repetition rate, and pulse energy, were identified. Furthermore, the effects of pulsed CO₂ laser welding parameters on weldability were also investigated. The study shows that through the proper selection of welding parameters, it is possible to produce visually sound welds where porosity is still unavoidably formed. It was observed that decreasing the welding speed could reduce the porosity within the visually sound welds.     

Repetitive operation of switchless transverse flow transversely excited atmosphere CO2 lasers

The enhanced preionisation efficiency of a mutually coupled parallel spark preioniser has been exploited to achieve switchless operation of a transversely excited atmosphere (TEA) CO(2) laser in the conventional transverse gas flow configuration. This made the laser more compatible to repetitive operation and the satisfactory performance of a switchless TEA CO(2) laser of ~8 cc active volume is reported here up to a maximum repetition rate of 100 Hz at a gas replenishment factor of ~2.     

Technique for measuring the beam shape of pulsed lasers

A simple technique for the measurement of the beam shape parameters of pulsed lasers, with just a single pulse of the laser is described. It involves the use of several beam dividers inclined at very small angles to the beam axis, reflecting the beam back to a screen or a phosphor placed near the exit of the laser. The reflected images are then photographed by a camera to yield the beam parameters.     

Monitoring of high-power CO2 laser cutting by means of an acoustic microphone and photodiodes

Laser cutting is nowadays a well-established sheet metal processing method. The cutting of thick plates (>15 mm) is, however, still characterized by more narrow process windows compared to those for thin sheets. Therefore good cutting quality cannot always be guaranteed. The development of a monitoring system that can measure the cut quality on-line could form a solution to this problem. In this study, the determination of an appropriate monitoring system is dealt with. The applicability for monitoring purposes of two types of sensors is investigated: the microphone and the photodiode. For both types, correlation between the sensor output and the cut quality is investigated. Besides contour cutting, piercing is also covered in the study. The full break-through of the piercing can be monitored by both sensors. Furthermore quantitative relations between cut quality parameters and photodiode signal parameters could be determined.     

Nd3＋：YAG脉冲固体激光器的研制

本论文结合实验需要,根据激光器的基本原理设计了一套脉冲固体激光系统。通过本论文。对固体脉冲激光器的一些基本原理。基本组成。调Q理论和选模理论有了更清晰的认识,并基本掌握了Nd3＋：YAG脉冲激光器选择输出模式的方法。     

便携式CO2红外分析器检测室内环境时的使用方法

室内空气中CO2 浓度的高低可以反映室内有害气体的综合水平,也可反映出室内通风换气的实际效果。中华人民共和国《室内空气质量标准》GB/T1 8883—2 0 0 2规定CO2 的检测方法为不分光红外气体分析法。本文介绍一种国产便携式红外分析器在检测室内环境时的使用方法。1　仪器简介     

Precise measurements of the total concentration of atmospheric CO2 and 13CO2/12CO2 isotopic ratio using a lead-salt laser diode spectrometer

We have developed a tunable diode laser spectrometer, called SIMCO (spectrometer for isotopic measurements of CO(2)), for determining the concentrations of (12)CO(2) and (13)CO(2) in atmospheric air, from which the total concentration of CO(2) and the isotopic composition (expressed in delta units) delta(13)CO(2) are calculated. The two concentrations are measured using a pair of lines around 2290.1 cm(-1), by fitting a line profile model, taking into account the confinement narrowing effect to achieve a better accuracy. Using the Allan variance, we have demonstrated (for an integration time of 25 s) a precision of 0.1 ppmv for the total CO(2) concentration and of 0.3[per thousand] for delta(13)CO(2). The performances on atmospheric air have been tested during a 3 days campaign by comparing the SIMCO instrument with a gas chromatograph (GC) for the measurement of the total CO(2) concentration and with an isotopic ratio mass spectrometer (MS) for the isotopic composition. The CO(2) concentration measurements of SIMCO are in very good agreement with the GC data with a mean difference of Delta(CO(2))=0.16+/-1.20 ppmv for a comparison period of 45 h and the linearity of the concentration between the two instruments is also very good (slope of correlation: 0.9996+/-0.0003) over the range between 380 and 415 ppmv. For delta(13)CO(2), the comparison with the MS data shows a larger mean difference of Delta(delta(13)CO(2))=(-1.9+/-1.2)[per thousand], which could be partly related to small residual fluctuations of the overall SIMCO instrument response.     

反可见、中红外、透10.6 μm高能激光分色镜的研制

介绍了利用离子辅助在ZnSe基底上沉积YbF3和ZnSe制作反可见、中红外、透10.6 μm高能激光分色镜的理论和工艺方法.采用红外优秀的镀膜材料YbF3替代传统的有放射性红外镀膜材料ThF4用于制作反可见、中红外、透10.6μm高能激光分色镜取得了较好的效果.同时所研制的分色镜在透射率、反射率,吸收等光学性质,应力硬度牢固度等力学性质,和抗高能激光损伤阈值等方面进行了一系列的测试,基本达到理想的指标.     

正确掌握日光温室中二氧化碳增施技术

随着生活水平的提高,露地生产远远不能满足人们在冬春淡季对蔬菜的需求,因而日光温室近年来迅猛增长.但在密闭的日光温室大棚中,二氧化碳严重不足,使得蔬菜、水果、花卉等经济作物经常处于二氧化碳饥饿状态,不能进行充分的光合作用.从而造成产量不高,病虫害、畸形果增多,影响农民的收入.     

Effect of external constraint on the characteristics and behavior of the plasma plume during high-power CO2 laser welding

Laser-induced plasma has been one of the hotspots of high-power CO₂ laser welding for many years. A novel method was proposed to suppress the plasma plume through external constraints, which resulted in more stable welding process and slightly increased penetration depth. Based on high-speed camera and image processing technology, it was demonstrated that the expansion of plasma plume both in height and width was suppressed by a pair of water-cooled copper blocks laid near laser incident point along the direction of seam. Besides its intensity and size, the dynamical behavior of plasma plume under spatial constraint was observed and analyzed by the characteristic parameters. The constraint mechanism and influence of the spacing between the two copper blocks was discussed. Results showed that external constraint was effective to suppress plasma plume, stabilize welding process, and to increase weld penetration for high-power CO₂ laser welding.