355nm Nd∶YAG激光在H_2中的高效一级斯托克斯转换

对脉冲Nd∶YAG激光(355 nm)在H2和H2∶He-Ar混合气体中的受激拉曼散射(SRS)进行了研究。在0.5 MPa的氢气中,同时测量到从二级反斯托克斯到三级斯托克斯的多波长输出,其总转化效率达88%;而高压下只剩下一级和二级斯托克斯输出,其中二级斯托克斯最大能量转化效率达44%(对应量子效率为63%)。由于高级斯托克斯的竞争,纯氢气中一级斯托克斯的最大能量转换效率不超过43%。通过向3 MPa氢气中掺入2 MPaAr气后,很好地抑制了二级斯托克斯的产生,从而获得了能量转换效率高达71%(对应量子效率为83%)的一级斯托克斯输出。对四波混频和级联受激拉曼散射在氢气多级斯托克斯产生中的作用以及惰性气体对它们的影响进行了讨论。     

355 nm Nd:YAG激光在H2中的高效一级斯托克斯转换

对脉冲Nd:YAG激光(355 nm)在H2和H2:He-Ar混合气体中的受激拉曼散射(SRS)进行了研究.在0.5 MPa的氢气中,同时测量到从二级反斯托克斯到三级斯托克斯的多波长输出,其总转化效率达88%;而高压下只剩下一级和二级斯托克斯输出,其中二级斯托克斯最大能量转化效率达44%(对应量子效率为63%).由于高级斯托克斯的竞争,纯氢气中一级斯托克斯的最大能量转换效率不超过43%.通过向3 MPa氢气中掺入2 MPaAr气后,很好地抑制了二级斯托克斯的产生,从而获得了能量转换效率高达71%(对应量子效率为83%)的一级斯托克斯输出.对四波混频和级联受激拉曼散射在氢气多级斯托克斯产生中的作用以及惰性气体对它们的影响进行了讨论.     

准分子激光拉曼种子源

对准分子激光拉曼种子源进行了深入研究。采用波导型拉曼地增强拉曼转换，并在氢气中掺入一定比分的氦气来控制向各阶斯托克斯光的能量转换。当无掺杂时，获得一阶斯托克斯光的最大转换效率η＿（ｍａｘ）＝３７％。当在氢气中掺入氦气比分为５％时，在泵浦能量范围５０～８０ｍＪ内获得一阶高转换效率（η＇≥９５％η＿（ｍａｘ）），二阶及高阶斯托克斯光的转换受到抑制。对实验结果进行了理论分析。     

掺氢比对天然气HCCI燃烧特性和排放的影响研究

利用CHEMKIN软件,对掺氢比例为10%、15%、20%和25%的天然气混合燃料对HCCI内燃机燃烧特性的影响进行模拟,并对其进行数据分析。结果表明:(1)氢气比例不同,可对天然气的燃烧速率产生影响;比例为10%时,对天然气的燃烧过程影响不明显,却显著提前了天然气燃烧时的着火时刻,但随着掺入氢气比例的增加,着火时刻提前的现象逐渐推迟。(2)随着掺氢比例的逐渐增加,缸内压力、缸内温度、中间产物CO的排放量的峰值均逐渐减小;累积气相反应放热量逐渐减小;掺氢热效率和气相反应净产热量在氢气的掺入比为10%～15%之间时达到峰值。(3)在尾气排放中,随着掺氢比例的增加,CO_2生成时刻提前,生成量未改变;NO含量的峰值和排放量随着掺氢的比例增加而增加。     

基于空芯光纤中氢气级联SRS的红绿蓝色激光

报道了基于充气负曲率空芯光纤的红绿蓝色拉曼激光实验。利用1064nm亚纳秒微片脉冲激光器抽运一段充高压氢气的Ice-cream型负曲率空芯光纤,通过氢气分子的级联受激拉曼散射,同时获得了波长分别为737.6,564.2,457.1nm的一阶、二阶、三阶振动反斯托克斯激光输出。通过调节抽运激光功率和气体气压,可以控制红、绿、蓝三色激光的相对强度和输出模式。     

连续波1.7 μm全光纤气体拉曼激光光源

报道了第一个连续波全光纤气体拉曼激光光源.采用实芯单模光纤与带隙型空芯光纤熔接的方法,制备了长度为50 m、充高压氢气的全光纤结构气体腔,以一个高功率连续波1540 nm光纤放大器为泵浦源,利用氢气分子的纯转动受激拉曼散射有效实现了 1693 nm斯托克斯连续激光输出.进一步,通过在气体腔输出端熔接一个中心波长为154...     

基于Sagnac干涉仪的保偏光子晶体光纤氢气传感器

提出了一种基于Sagnac干涉仪的保偏光子晶体光纤(PM-PCF)氢气传感器,建立了传感模型并进行了实验研究和验证。采用对靶磁控溅射技术将钯银(Pd/Ag)合金快速均匀地沉积在保偏光子晶体光纤侧面,并利用Pd吸收氢气后的形变调制保偏光子晶体光纤的双折射,通过测量Sagnac干涉仪输出光谱峰值的变化实现氢气浓度的测量。实验结果表明该传感器可检测的氢气浓度范围为0%~4%,且具有良好的重复性。室温下对低浓度氢气具有较高的灵敏度,氢气浓度由0%变化到1%时的波长偏移量达1.307nm。采用双折射温度不敏感的保偏光子晶体光纤,可很好地抑制外界温度变化对传感器的干扰。     

基于空芯光纤中氢气受激拉曼散射的1.7μm光纤激光光源研究

报道了一种基于空芯光子晶体光纤中氢气受激拉曼散射的新型1.7μm光纤激光光源。建立了仅包含泵浦光和一阶斯托克斯光的简单稳态耦合波方程,并进行了仿真计算。采用自制的1550 nm纳秒脉冲光纤放大器,泵浦一段长约3 m、充高压氢气的商用空芯光子晶体光纤,利用氢气分子的转动受激拉曼散射实现了1705 nm斯托克斯波的有效转换。气压为1.2 MPa时,最大平均输出功率约0.5 W(单脉冲能量约为2.5μJ),最大光光转换效率约为32%(相对总的泵浦功率)。研究结果为实现高功率1.7μm波段近红外激光输出提供了一条有效的新途径。     

一种紧凑型高功率脉冲调制器

研制了一种基于水介质单同轴脉冲形成线型的高功率脉冲调制器,该调制器由初级储能电容器、脉冲变压器、水介质同轴脉冲形成线、氢气主开关和场发射真空二极管等组成。用Pspice电路软件对脉冲形成线的充电电压和二极管电压、电流进行了模拟,并用有限元软件分析了脉冲形成线的电场分布。当初级储能电容器组充电电压为35 kV, 氢气主开关导通电压高达520 kV时,在调制器场发射二极管输出电压约230 kV, 束流30 kA,脉宽约60 ns的高电压脉冲。此外,对主开关充不同类型的气体进行了实验研究,结果表明:氢气主开关的脉冲调制器能够在二极管上获得前沿更陡的高电压脉冲,并能有效地改善二极管电子束的性能。理论分析与实验结果基本一致。此种类型的调制器具有运行稳定、体积小、结构紧凑的特点。     

蓝绿光激光器现状

结合最近几年国际上研制蓝绿光激光器的主要进，介绍了实现蓝绿色激光输出的几个途径，即：（１）在线性光学晶体倍频方法；（２）研制宽带隙半导体材料激光器；（３）掺入稀土离子，利用上转换效应发射蓝绿激光。     

掺氢与激励电路对钡蒸气激光输出特性的影响

对用Blumlein电路放电激励的钡蒸气激光在掺氢和不掺氢时的输出特性进行了实验研究.结果表明，用掺氢1.5%的氖气作缓冲气体能使激光功率增加近2倍.在此基础上，进一步比较了相互作用电路与Blumlein电路时钡蒸气激光的输出特性，发现相互作用电路能显著提高钡蒸气激光的输出功率和效率，获得了3W最大功率和0.4%效率的1.5μm波长激光输出.测量并分析了各工作参量与激光功率之间的关系，定性解释了掺氢与相互作用电路的作用机理 . 关键词： Blumlein电路 相互作用电路 掺氢 钡蒸气激光     

Pulsed barium vapor laser with hydrogen additive and interactive circuit

A small-size discharge heated barium vapor laser with an axial temperature controller was designed and made. The operational characteristics of the laser with different hydrogen additives and two excitation circuits were experimentally investigated and compared. The results indicate that the addition of a small ratio (1.5%) of hydrogen to neon and the interactive circuit (IC) can greatly increase the laser output power. The maximum average laser power of 3.5 watts and a record specific power of 117.3 mW/cm³ at a 1.5 μm wavelength were obtained under optimal discharge conditions. Some possible mechanisms were suggested to explain the enhanced effect of the hydrogen additive and IC to the laser output performances. PACS 42.55.Lt; 42.60.Lh; 52.80.Tn     

Modeling the plasma kinetics mechanisms of CuBr laser with neon–hydrogen additives

A mathematical model describing the discharge kinetics and lasing characteristics of copper bromide vapor laser with neon and hydrogen additives has been developed. The suggested model is based on a “zero-dimensional” model and offers simple mechanisms to explain discharge kinetics mechanisms, different physical processes and hydrogen additive effects on the copper bromide vapor laser.The model estimates the temporal evolution of discharge voltage and current, population densities, laser beam density, electron temperature and radial distribution of pressure and buffer gas temperature. The suggested mechanism assumes that the electron detachment from negative hydrogen ions does not contribute to the copper ionization process.Numerical solutions of a nonlinear rate equation system predict the generation of nanosecond pulses. The calculated maximum values of discharge voltage, current, average output laser power, electron temperature, etc. are in good agreement with other reported calculated and experimental data.     

高重复率铜蒸汽激光的充氢机制

通过数值求解时空自洽的铜蒸汽激光动力学方程，详细研究了铜激光的充氢机制．少量充氢提高激光功率的原因是：1）氢具有的大热导率使管壁温度升高，铜粒子数密度增加；2）充氢增加了电子与氢的动量输运碰撞，使放电电流减小．当电源功率一定时，闸流管的功率损耗减小，输入激光管的功率增大．此外，充氢过多（大于（1—2）%氖），通过电子碰撞激发氢分子振动能级，使电子温度和电子密度下降较大，电子没有足够的能量密度激励激光能级，导致激光功率下降 关键词：     

Improved sonolytic hydrolysis of peptides in aqueous solution with addition of 1,4-benzenedithiol

Described here is the sonolytic hydrolysis of peptides achieved by treatment of aqueous solution to which the radical scavenger 1,4-benzenedithiol (1,4-BDT), which has hydrogen donating ability, has been added. Mass spectrometric analysis of the products of sonolytic hydrolysis gave information about amino acid sequence of the peptides without any byproducts. The additive 1,4-BDT improves the sonolytic hydrolysis of peptides in terms of the rate of hydrolysis reaction and the amount of additive required when compared to catechol, a previously reported additive. The sonolytic hydrolysis of peptides differs from both acid hydrolysis and hydrogen atom-induced dissociation named matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD), in characteristics. We propose a mechanistic reaction for the sonolytic hydrolysis of peptides, based on the mechanisms of both acid hydrolysis and MALDI-ISD processes. The sonolytic hydrolysis of peptides upon addition of hydrogen donating radical scavengers can be rationalized via the attachment of a hydrogen atom to the carbonyl oxygen with subsequent hydrolysis.     

Characteristics of copper HyBrID-type lasers which use HCl reactive gas

We have investigated the output behaviour of a low temperature HyBrID-type copper laser operating with a flowing Ne–HCl reactive gas mixture. 15.5 W of average power was observed from a 19 mm bore device at 23 kHz PRF corresponding to a specific output power of 78 mW/cm3. The output power was 20–30% lower than that of the same device operating with an Ne–HBr mixture; however, it markedly exceeds the output of similar sized elemental copper vapour lasers (with or without hydrogen additive). This revised version was published online in June 2006 with corrections to the Cover Date.     

Enhanced performance of a wide-aperture copper vapour laser with hydrogen additive in neon buffer gas

A wide-aperture copper vapour laser was demonstrated at ∼10 kHz rep-rate with hydrogen additive in its buffer gas. Maximum power in excess of ∼50 W (at 10 kHz) was achieved by adding 1.96% hydrogen to the neon buffer gas at 20 mbar total gas pressure. This increase in output power was about 70% as compared to ∼30 W achieved with pure neon at 5.5 kHz rep-rate. The 70% enhancement achieved was significantly higher than the maximum reported value of 50% so far in the literature. The enhancement was much higher (about 150%) as compared to its 20 W power at 10 kHz rep-rate using pure neon as the standard CVL operation.     

Modulation enhancement of a laser diode in an external cavity

The influence of Zn-atom additive on ‘pure’ copper vapor laser output characteristics is studied. The laser pulse width, energy and power are found to increase under the diffusion of zinc atoms from a zinc-containing reservoir into the discharge of the copper-vapor laser at temperatures above 500°C. Additional absorption experiments and calculations are consistent with the conclusion that not only optical resonant pumping by the 213.9-nm Zn I line, but also other processes, should be taken into account to explain the effects of additive influence.     

Copper-vapour laser with silver additive

Results of experimental investigation of a pure elemental copper-vapour laser with silver additive are reported. Average output power as well laser output pulse energy increased by up to 10% with the additive. A possible mechanism of additive influence on laser output parameters is discussed.     

An updated overview of diamond-like carbon coating in tribology

During the last two decades, the industry (including scientists) has focused on diamond-like carbon (DLC) coating because of its wide range of application in various fields. This material has numerous applications in mechanical, electrical, tribological, biomedical, and optical fields. Severe friction and wear in some machine parts consumes high amount of energy, which makes the process energy inefficient. Thus, DLC coating can be an effective means to lower the friction and wear rate. Some important process variables that affect the tribological characteristics of DLC coating are adhesion promoter intermediate layer, substrate surface roughness, hydrogen incorporation or hydrogen non involvement, and coating deposition parameters (e.g., bias voltage, etching, current, precursor gas, time, and substrate temperature). Working condition of DLC-coated parts also affects the tribological characteristics, such as temperature, sliding speed and load, relative humidity, counter surface, and lubrication media (DLC additive interaction). Different types of lubricated oils and additives are used in engine parts to minimize friction and wear. DLC can be coated to the respective engine parts; however, DLC does not behave accordingly after coating because of lubricant oil and additive interaction with DLC. Some additive interacts positively and some behave negatively because of the tribochemical reactions between DLC coating and additives. Numerous conflicting views have been presented by several researchers regarding this coating additive interaction, resulting in unclear determination of true mechanism of such interaction. However, lubricant additive has been established to be more inert to DLC coating compared with uncoated metal surface because the additive is fabricated in such a way that it can react with metal surfaces. In this article, the tribological characteristics of different types of DLC coating in dry and lubricated conditions will be presented, and their behavior will be discussed in relation to working condition and processing parameters.