Assembly structure convective—flow CO laser

This article describes a convective-flow CO laser composed of quartz tubes, nickel–chromium steel components, a copper heat exchanger, polytetrafluoroethylene tubes and other components. The method of vacuum sealing between quartz tubes and nickel–chromium steel pipes by polytetrafluoroethylene tubes enables the laser to operate with liquid nitrogen cooling. An output of 120 W has been obtained by adopting a non-selective cavity.     

溶液浇铸法制备氘代聚乙烯薄膜

采用改进的溶液浇铸法,用氘代聚乙烯为原料,制备了厚度为100, 200, 400 μm的氘代聚乙烯薄膜。研究了溶液温度、干燥温度、真空加热温度及时间等因素对成膜性、薄膜均匀性和透明性的影响,确定了最佳工艺条件:溶液温度120～130 ℃,干燥温度80～100 ℃,加热温度120 ℃,加热时间1 h。3维视频显微镜和原子力显微镜表征结果表明:制备的薄膜透明性较好,厚度较均匀;薄膜表面起伏较小。     

Magnetically confined discharge CO laser

Under the condition of magnetic confinement, the paper analyzes the following discharge processes from CO gas: (1) the variation of electron energy distribution; (2) the impact excitation rates of electron for the vibrational CO molecules; and (3) the vibrational-state population of CO molecule and small-signal gain. Our results show that, by adding magnetic field, the electron density increases greatly in the energy region corresponding to the maximum electron cross sections of CO molecule, while the electron impact on excitation rates also increases. At the same time, the vibrational-state population of CO molecule and the laser small-signal gain of every vibrational level are also higher than that without magnetic field.     

Wideband CO laser in problems of laser sensing of minor gaseous components in the atmosphere

In the present work it is demonstrated that a wideband CO laser operating at fundamental and overtone vibrational transitions is a promising source of laser radiation for remote laser sensing of the atmosphere. A compact slab RF-discharge CO laser has been designed. The optimal operating conditions are determined for this CO laser. In experiments, the maximum average output laser power was ∼12 W for lasing efficiency of ∼14%. Under fixed experimental conditions, stable lasing (with fluctuations of the output laser characteristics ≤5%) was observed during more than one hour, which suggests that we first excited the sealed-off mode of cryogenic slab RF-discharge CO laser. The frequency-selective mode was first obtained for this laser. Wavelengths for sensing of nitrous oxide, nitrogen dioxide, methane, formaldehyde, and some other gases on near-ground propagation paths are determined. Our experiments and calculations confirm that this CO laser is promising for laser gas analysis. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 76–83, November, 2008.     

Multiline laser probing of CO:He, CO:N2, and CO:O2 active media in a wide-aperture pulsed amplifier

Multiline laser probing was applied for the diagnostics of the active medium of a wide-aperture carbon monoxide laser amplifier. The temporal behavior of the small-signal gain in the active medium of a pulsed electron-beam sustained discharge CO laser amplifier was studied with a specially designed probe CO laser in a wide range of ro-vibrational spectral lines (from V = 5 up to V = 31). The results were analyzed in order to reconstruct the temporal behavior of gas temperature and vibrational populations in CO-containing gas mixtures, CO:He and CO:N₂, and oxygen-rich CO: O₂ mixtures. __________ Translated from Preprint No. 13 of the P. N. Lebedev Physical Institute, Moscow (2005).     

CO2激光调Q技术

调Q技术是实现小型CO₂激光器短脉冲输出的重要手段,近年来随着短脉冲CO₂激光器在激光测距、测速、成像雷达、环境探测、空间通讯及激光与物质相互作用等领域应用需求的不断增长,激光调Q技术越来越受到国内外专家的关注而成为红外激光技术的研究热点之一。本文就目前用于CO₂激光器中实现短脉冲输出的5种主要调Q技术（机械调Q技术、电光调Q技术、声光调Q技术、被动调Q技术、复合调Q技术）的国内外发展历程和现状进行了综合评述,总结分析了各种方法的关键技术和存在的问题,并简要分析了该技术的未来发展趋势。     

气压对吸气式激光推进冲量耦合系数的影响

保持CO2激光的单脉冲能量为61.4~64.6 J，采用高精度冲击摆系统进行了不同气压下吸气模式激光推进冲量耦合系数的实验测试，分析了对应的高度特性。结果表明:气压为2.8×104～1×105 Pa，即距离地面0～10 km时，冲量耦合系数大约3.5×10-4 N·s·J-1，上下波动幅度低于5%；气压低于2.8×104 Pa，即高度大于10 km时，冲量耦合系数呈二次曲线显著下降；当气压降至1×103 Pa，即距离地面约31 km高度时，耦合系数仅为9.7×10-5 N·s·J-1。     

金属材料的激光吸收率研究

针对菲涅耳公式计算金属材料激光吸收率所得的结果与实际测得的吸收率值存在一定的误差这一问题,在详细分析了激光热处理中金属材料吸收率影响因素的基础上,通过数值模拟,改进了金属材料激光吸收率的计算模型,并利用此激光吸收率计算模型(以铝、铜、铂、铁4种金属材料为例)进行激光吸收率的计算和分析,进而计算了3Cr13不锈钢激光吸收率的理论值,该值与用集总参数法测得的3Cr13不锈钢材料激光吸收率结果相吻合,从而验证了该改进的金属材料激光吸收率计算公式的正确性。     

声光调Q CO2激光器的输出特性

采用谐振腔内插入声光调制器（AOM）的方法获得了小型CO2激光器的高重频、窄脉宽、高峰值功率输出。通过分析CO2激光器声光调Q的工作原理,利用基于小信号增益和饱和光强的耦合输出数学模型给出了激光器最佳输出镜透过率的数值解,并运用相关实验装置对该数学模型进行了实验验证。理论分析和实验结果均表明：该声光调Q CO2激光器的最佳输出镜透过率为39%。研究了激光器输出性能随脉冲重复频率的变化规律,当脉冲重复频率〉1 kHz时,激光器输出峰值功率下降,这与CO2分子上能级寿命有关,并受声光调Q开关热效应的影响。实验中获得的激光器脉冲频率在1 Hz～100 kHz可调。在脉冲频率为1 kHz时,获得的激光脉冲宽度为156 ns,脉冲峰值功率为10 kW,且稳定性较好,非常适合于作激光与物质相互作用的光源。     

RF discharge slab CO laser operating in both fundamental and first-overtone bands

A compact sealed-off cryogenically cooled radio frequency (RF) discharge slab CO laser, operating in both first-overtone (FO) and fundamental band (FB), was launched. Repetitively pulsed and CW modes of RF discharge excitation were studied. Average FB output power was up to 12 W, with laser efficiency 14%. The multiline FB laser spectrum was observed within the wavelength range ∼5.1-5.4 μm. An optical scheme “frequency selective master oscillator - laser amplifier” was applied for getting FB tuning. Single line FB lasing with average power up to several tens of mW was observed on ∼100 FB vibrational-rotational transitions of CO molecule within the spectral range ∼5.0-6.5 μm. Multiline FO lasing was observed on ∼80 spectral lines within the spectral range ∼2.5-4.0 μm, with maximum single line average output power 12 mW. Total output power of the slab FO CO laser came up to 0.3 W, with maximum laser efficiency 0.5%. Results of parametric studies of the FB and FO slab CO laser including complicated time behavior for laser pulses on different FO vibrational-rotational transitions are discussed.     

高功率TEA CO2激光器两波长激光切换输出技术

 以TEA CO₂激光器通常采用的平-凹光学稳定腔为基础,提出了一种新的波长选支方法——输出窗口镀膜选支方法。利用一台高平均功率TEA CO₂激光器进行了选支实验研究,结合现有光学镀膜技术,得到了中心波长为9.3 μm的激光单谱线输出,其单脉冲能量及平均功率与激光器原中心波长10.6 μm单谱线输出的相应参数基本相当。研究发现,以相同单脉冲能量激光照射热敏纸时,中心波长9.3 μm激光光斑与中心波长10.6 μm的明显不同。同时,还设计出两波长窗口密闭免调切换装置,在一台激光器上实现了10.6,9.3 μm两个中心波长激光同等功率水平的免调切换输出,切换位置误差小于5″,密封性能满足使用要求。     

管状预电离可调谐TEA CO2激光器.

研制了一种新型的预电离结构--管状预电离器,并将其应用于可调谐TEA CO2激光器.利用光栅选线方案,采用光栅谐振腔,实现了激光的调谐输出.在输出耦合率为50%、气压为40 kPa的条件下,10P(20),10R(20),9P(20),9R(20)四条谱线获得的最高电光转换效率,分别为9.5%,9.7%,9.8%,9....     

Deep penetration welding using a CO laser with an unstable resonator

An unstable resonator (M = 2) has been applied to reduce the beam divergence of a gas-dynamically cooled supersonic CO laser operating at 105 K in a semiclosed gas cycle. A 4.7 kW laser beam with a total divergence of 2.5 mrad is obtained with an efficiency of 9.4%. The results of welding experiments are compared with those using a CO₂ laser. The weld depths obtained with the CO₂ laser are drastically reduced using argon as the assist gas, whereas the results with the CO laser are independent of the assist gas because of the lower plasma absorption coefficient for the shorter CO laser wavelength.     

板料激光成型技术的实验研究

激光成型是一种利用激光作为热源的热应力无模成型新技术。介绍了板料激光成型技术的工艺过程及影响激光成型的主要因素 ,通过实验研究了激光能量因素、板料的材料性能及几何参数对板料弯曲角度的影响     

Time-resolved spatial structure of TEA CO2 laser pulses

The evolution of the intensity profile of TEA CO₂ laser pulses along the pulse length is investigated both analytically and experimentally. A simple scalar model of the pulse amplitude is introduced, which gives the loaded-cavity modes as a linear combination of bidimensional Hermite-Gauss functions. According to this model a number of equations are derived which link the time-varying spatial structure of the pulse to its time-resolved second-order intensity moments, namely, the beam width and the M² parameter.     

Electrical parameters retrieval of carbon nanoparticle-based metal semiconductor metal structure by standard methods and beta-ray-induced charge

Semiconducting carbon nanoparticles (CNPs) represent various applications in sensing systems with exceptional electronic properties. The extraction of electronic parameters of a sensor is very important to interpret the sensing characteristics of the electronic devices. This work is concerned with the extraction of electronic parameters such as the ideality factor, the barrier height, the series resistance, and some other diode parameters of a CNP-based metal semiconductor metal structure. The parameters are determined from the experimental data and physical model using the standard current–voltage (I–V) analysis in the frame of the thermionic emission theory, impedance spectroscopy, and other methods. The mobility-lifetime products (μτ) for electrons and holes in CNP micro-wire were determined by beta-ray-induced charge with Schottky contacts.     

激光辐照环境对金属材料反射特性的影响

 利用积分球绝对测量法,对在20 Pa真空缺氧、1 000 Pa空气,10⁵ Pa空气及1 000 Pa氧气环境下,1 064 nm波长连续激光辐照30CrMnSiA碳钢材料过程中的反射光信号进行了测量,得到了30CrMnSiA碳钢在4种辐照环境下的反射率和温度变化曲线。结果表明：在空气组分辐照环境的低压到10⁵ Pa范围内,材料初始反射率随压力增大而增大;在缺氧和富氧环境的激光辐照过程中,缺氧环境下材料反射率变化缓慢,且变化拐点温度高于富氧环境,富氧环境下材料被加热后的快速氧化反应有利于材料对激光能量的吸收;不同辐照环境（缺氧和富氧）相同材料温度条件下,材料反射率并不相同。     

纳秒激光烧蚀下液态金属表面微结构的形成

首次发现了在不同保护气体及多脉冲uV—IR激光的照射下,液态金属的微型突起和微结构的形成。测量表明,针对不同的金属和保护气,这种结构的单脉冲生成速率可达（5—20）μm／pulse,形成了长度为1～2mm,直径约为焦点两倍的单个微型突起。最后,介绍了控制微结构形状的可能性,并讨论了它们的应用潜力。     

Analysis of the spectral structure of CuBr laser lines

The spectral structure of spontaneous emission of copper atom at 510.6 nm and 578.2 nm was calculated considering the hyperfine structure of energy levels and the isotope shift. The spectral structure of the 510.6 nm and 578.2 nm laser lines was measured in a sealed-off CuBr laser tube with periodic refreshment of the neon buffer gas under different work temperature and excited voltage. The spectral structure of the spontaneous emission of copper atom was found to have similar outline with its laser lines. The spectrum of the 510.6 nm laser line maintains similar outline with three peaks at various discharging parameters while the spectrum of the 578.2 nm laser line is strongly dependent on the reservoir temperature and the discharge voltage.     

Dynamical study on charge injection and transport in a metal/polythiophene/metal structure

The dynamical process of charge injection from metal electrode to a nondegenerate polymer in a metal/polythiophene （PT）/metal structure has been investigated by using a nonadiabatic dynamic approach. It is found that the injected charges form wave packets due to the strong electron-lattice interaction in PT. We demonstrate that the dynamical formation of the wave packet sensitively depends on the strength of applied voltage, the electric field, and the contact between PT and electrode. At a strength of the electric field more than 3.0 × 10^4 V/cm, the carriers can be ejected from the PT into the right electrode. At an electric field more than 3.0 × 10^5 V/cm, the wave packet cannot form while it moves rapidly to the right PT/metal interface. It is shown that the ejected quantity of charge is noninteger.