一种模拟二极管激光源场的新方法

基于非傍轴衍射理论和二极管激光远场光强的实验结果,借助于振幅-位相恢复算法,提出了模拟二极管激光源场分布的一种新方法.给出了模拟步骤,并以双异质结二极管激光为例加以说明.当实验结果准确时,这是一种足够精确的方法,有实际应用意义. 关键词： 二极管激光 源场分布 模拟退火法     

Population of molecules as strongly anharmonic oscillators in a diatomic gasdynamic laser

Population distribution is studied quantitatively for a diatomic gasdynamic laser in which the molecules behave as strongly anharmonic oscillators under the action of a Morse internuclear potential. In fact, mathematical relationships concerning the two fundamental parameters associated with anharmonicity are derived.     

New results on gas density, velocity field, and force field of a gasdynamic laser within a supersonic nozzle

Several new results are derived upon gas density as well as upon velocity and force fields relative to a gasdynamic laser within a supersonic nozzle. Evolution equations, including the continuity equation, are employed to obtain the above results. In particular, the continuity equation is used to determine the shape of the nozzle so that its cross-sectional area is calculated as a function of distance. This function is one of the ingredients to get our results relative to gas density, velocity, and force. In addition, the time-dependent power associated with the vibrational non-equilibrium expansion in the nozzle of hot gas at high pressure is evaluated.     

少周期XUV激光中氢分子离子单光子电离理论研究

通过数值求解二维含时薛定谔方程研究了氢分子离子在圆偏振XUV少周期激光电场中的单光子电离,结果观察到不同核间距的氢分子离子的光电子能谱的能移现象.分析表明,在少周期激光场宽频情况下,分子电离电子的双中心干涉改变了夫兰克-康登因子的单调递减趋势,使不同核间距氢分子离子的光电子能谱出现能量移动.     

基于发射光谱的DF激光器光腔温度与粒子数分布

建立了谱线增益系数与温度、粒子数分布之间及谱线增益系数与谱线强度之间的关系式,对一台燃烧驱动DF激光器的发射光谱进行了测量,利用发射光谱数据计算得到光腔温度为381.4 K,分布在振动态能级1与0,振动能级2与1,振动能级3与2的粒子数之比分别为0.60～0.62, 0.676 4, 0.71～0.74。     

大口径DKDP元件的辐照损伤分布特性

大口径高能激光装置是各强国积极研究的重点项目。对装置内大口径光学元件损伤特性进行有效评估具有非常重要的意义,在此研究大尺寸光学元件表面损伤。通过分段拍摄、图像拼合、损伤点记录、统计与归纳等工作发现,不同尺寸损伤点的分布特性差异较大。结合统计学方法与类似实验对比、理论计算等方式对损伤点分布与样品辐照环境特性变化的关系进行分析。结果显示,损伤点的位置分布与辐照光束的能量密度关联紧密;系统光束(351 nm)在低于6 J/cm²时能量分布均匀,高于6.7 J/cm²时呈现较为明显的高斯分布状态。可以为大口径高能辐照环境的元件损伤特性评估提供有价值的参考,对大口径紫外激光器的日常运行与维护具有极其重要的工程意义。     

LD阵列侧面泵浦棒状激光介质内的光场研究

建立了LD侧面泵浦激光介质内的光场分布数值模型。通过光线追迹方法,简化了介质对泵浦光折射的计算方式。利用Matlab软件数值模拟了泵浦光在介质内的归一化分布。提出获得高质量、高能量的激光输出参数的选取原则。当LD的束腰半径为1μm、LD的数量为40个、介质的半径为1.5mm、发光面到介质的泵浦距离为0.5mm、介质吸收系数在2cm-1～6cm-1之间时,泵浦光在激光介质内的增益分布较好。     

A new design of pulsed laser diode driver system for multistate quantum key distribution

In this paper, we describe a new design of laser diode driver system based on MOSFET current mirror and digital signal controller (DSC). The system is designed to emit stream pairs of photons from three semiconductor laser diodes. The DSC is able to switch between the three laser diodes at constant rate. The duty cycle is maintained at 1% in order to reduce its thermal effect and thus prolong the laser diodes’ life cycles. The MOSFET current mirror circuits are capable of delivering constant modulation current with peak current up to 58 mA to each laser diode. This laser driver system will allow the generating biphotons automatically with qubit rate around 8-13% for μ less than or equal to 1, thus making it practical for six-states quantum key distribution implementation.     

Diagnostic system for two dimension intensity distribution of laser beam

The diagnostic system for two dimension(2-D)intensity distribution of laserbeam is a measuring instrument for many parameters of laser beam.2-D intensity distributionplot of laser beam is obtained by the two dimension scanning mirror which is controlled by amicrocomputer to scan the laser beam on a detector.Many parameters of laser beam such asthe isointensity distribution plot,the beam diameter,the beam waist diameter,the laser pow-er,the diverge angle and the beam brightness,are given by means of the microcomputer pro-cessing the data measured.Theoretical analysis of beam parameter transform is given.     

硅中钛杂质对激光电场分布影响的数值模拟

采用T-matrix数值方法模拟光学系统常用的光学材料硅中金属钛杂质对激光电场分布的影响。分析了不同球形杂质数目、不同杂质球半径、不同球形杂质间距、不同球形杂质排列以及不同相对介电常数杂质对激光电场分布的影响,通过数值模拟了解到：电场幅值的最大值总是出现在沿入射波极化方向上,电场幅值的增大与相邻两球的耦合有关,且两球间距越小电场幅值的最大值越大;相对介电常数实部越小、虚部越大的杂质会导致较大的电场幅值最大值。     

He—Ne激光器粒子数反转径向分布光谱测量

用二维光学多道分析仪考察了He-Ne激光器在632.8nm激光振动和不振荡时氖能级3s_2和2p_k(k=1,2,……8,10)的侧光辐射,进行了Abel反演后,得到了3s_2和2p_k各能级粒子数和3s_2和2p_k间粒子数反转的径向分布,研究了此分布勺放电电流、632.8nm激光辐射强度间的关系,推算了在放电管中心3s_2和2p_k能级间受激辐射的激光增益。     

飞秒激光-等离子体相互作用中快电子能量分布

 采用不同量程的电子谱仪与LiF热释光探测器相配合,测量了飞秒激光 等离子体相互作用中产生的快电子能量分布。结果显示快电子能量分布的一致性和多个重要特征与国外同类实验和计算机模拟结果相似。快电子能谱在低能处产生凹陷是由于冷电子的回流产生的;几种加速机制共同作用是能谱在100~350 keV范围内出现平台的原因;快电子的有效温度较好地满足共振吸收的温度定标律是由于反射激光加速与共振吸收机制均是通过朗道阻尼或波破对电子进行加速的。     

飞秒激光-等离子体相互作用中快电子能量分布

采用不同量程的电子谱仪与LiF热释光探测器相配合,测量了飞秒激光 等离子体相互作用中产生的快电子能量分布。结果显示快电子能量分布的一致性和多个重要特征与国外同类实验和计算机模拟结果相似。快电子能谱在低能处产生凹陷是由于冷电子的回流产生的;几种加速机制共同作用是能谱在100~350 keV范围内出现平台的原因;快电子的有效温度较好地满足共振吸收的温度定标律是由于反射激光加速与共振吸收机制均是通过朗道阻尼或波破对电子进行加速的。     

Theoretically study on measurement of velocity distribution by means of laser induced fluorescence

Based on two-level atomic density matrix movement equation and emitting operator, the physical model is established for laser induced moving atomic resonant fluores cence. Theoretically study showsthat the measurement of atomic velocity distribution by means of laser induced fluorescence is only valid when the physical factors, such as atomic natural line width, laser power, laser line width, is suitably selected.     

平方泵噪声驱动的单模激光立方模型及光强定态概率分布

合理地引入了平方泵噪声到单模激光的立方模型中. 得到封闭的光强朗之万方程. 基于作者早期关于非线性外噪声的近似福克-普朗克方程(AFPE)的工作，得到了光强概率分布的AFPE，求出了该AFPE的归一化定态概率分布的精确解析表达式，并根据表达式对泵噪声实部和虚部之间的关联系数λ的对称性，得出了若干关于系统定态统计性质的普遍结论. 关键词： 平方泵噪声 单模激光的立方模型 光强定态概率分布 统计性质重复出现     

高功率激光系统中随机分布缺陷产生的"热像"

基于"热像"的衍射理论模型,并利用空间频谱的传输矩阵,理论分析了位置和尺寸均随机分布的缺陷在高功率激光系统中产生"热像"的机理,作为理论分析结果的对比验证,数值模拟了高功率激光束受到这种随机分布缺陷调制后所形成"热像"的演化规律,进而从统计平均的角度讨论了"热像"强度的变化趋势与缺陷分布数目和尺寸范围之间的关系. 结果表明,当缺陷的尺寸接近某个特定值时,受其调制的光束会形成强度最大的"热像"点,且"热像"所在平面强度极大值点的横向位置与光学元件表面的缺陷横向分布相对应;在一定范围内,"热像"的强度最大值随 关键词： 热像 随机分布缺陷 高功率激光 非线性介质     

Effects of powder concentration distribution on fabrication of thin-wall parts in coaxial laser cladding

In this paper, model of effects of powder concentration distribution on fabrication of thin-wall parts in coaxial laser cladding was developed. There exists relationship between powder concentration distribution and power density distribution, which affects fabrication of thin-wall parts in coaxial laser cladding. Changes in powder concentration distribution lead to changes in wall thickness and wall growing rate. Fluctuation of powder feed rate deteriorates the growing wall in laser cladding. Deviation of the powder flow stream makes the powder concentration distribution, the thermal flux density and consequently the molten pool not symmetrical against the x-axis, resulting in irregular upper faces of the formed wall. This was verified by the results of experiment.     

Analysis of random laser scattering pulse signals with lognormal distribution

The statistical distribution of natural phenomena is of great significance in studying the laws of nature. In order to study the statistical characteristics of a random pulse signal, a random process model is proposed theoretically for better studying of the random law of measured results. Moreover, a simple random pulse signal generation and testing system is designed for studying the counting distributions of three typical objects including particles suspended in the air, standard particles, and background noise. Both normal and lognormal distribution fittings are used for analyzing the experimental results and testified by chi-square distribution fit test and correlation coefficient for comparison. In addition, the statistical laws of three typical objects and the relations between them are discussed in detail. The relation is also the non-integral dimension fractal relation of statistical distributions of different random laser scattering pulse signal groups.     

线状聚焦激光与金属作用的离子速度分布

本文报道了利用法拉第筒飞行时间法进行的离子测量.通过比较高功率激光线状聚焦和点状聚焦在平面金属靶上产生的离子发射特性,总结出离子速度分布和激光辐照密度的定标规律,以及离子速度分布的空间各向异性.实验是在上海光机所钕玻璃激光装置上进行的,激光束的波长为1.06μm,脉宽为300ps,辐照密度为10~(12)～10~(14)W/cm~2.     

高斯初始能量分布下自由电子激光饱和状态的统计理论求解

基于高增益自由电子激光饱和状态的统计物理方法,在不同的电子束相空间初始分布下对原有理论进行了发展和推广,借助于多重数值积分技术解决了粒子束一般动量初始分布带来的计算困难,并以更接近实际的高斯动量分布为例进行计算。作为对比验证编写高斯初始动量分布下的直接数值模拟程序,将高斯初始分布同"水袋"两种初始分布的"暖电子束"入射情形下自由电子激光达到饱和时系统的光强、聚束因子和粒子相空间分布均进行相应计算和比较。结果表明:数值模拟和统计计算结果相一致;在目前选取的参数范围内,两种初始分布的相应结果差异并不显著。