蒸汽激光及其相似性关系的研究

蒸汽激光是利用亚稳态氦原子H_θ(2~3S)或氦离子He~+为能量的载体,通过潘宁效应或转荷效应将亚稳态氦原子的激发能或氦离子的电离能交给低电离电位元素的原子,使其电离和激发。目前,蒸汽激光已有氦-镉激光、氦-锌激光、氦-硒激光、氦-碘激光、氦-汞激光、氦-碲激光和氦-铜激光等共有一百余条连续工作的激光谱线,波长在3250埃至1.26微米之间,最大功率可达200毫瓦以上。     

钇原子亚稳态寿命的测量

原子的寿命是原子的重要参数之一。本文的寿命测量方法涉及原子束中原子的速度分布的测量。理论和实验已经证实,对于原子束中原子速度分布的测量,采用激光感应荧光的方法比传统的机械斩波法方法更为方便,且具有更高的分辨率,尤其是对超声速的束流。在此基础上,利用基态原子无穷长的寿命以及亚稳态原子在飞行过程中的衰减,比较测量到的原子基态和亚稳态的速度曲线,可以确定原子亚稳态的寿命。其原理与束箔法测量相似。 在本文实验中,用激光感应荧光法测量到的是原子数密度的速度分布,即信号是:     

亚稳态氖原子光刻的实验研究

用亚稳态氖原子束进行了原子光刻实验。用栅网作掩膜 ,以扩散泵油的有机分子在高能亚稳态氖原子作用下所生成的碳膜作抗蚀剂 ,在硅片上刻蚀出分辨率为 2 μm的微结构 ,为进一步的纳米级原子光刻技术的研究打下了基础。     

原子光刻用亚稳态氖原子束源的研究

研制了一台用于原子光刻的亚稳态氖原子束源 ,其束流强度可达 3 3× 10 14 atoms/s·Sr.。研究了束流强度的变化规律 ,并对其机理进行了探讨。     

低噪音氦-镉激光器

人们在研究脉冲镉蒸汽激光器的实践中,发现以氦作为该激光器的缓冲气体有特殊作用.氦亚稳态和氦离子与镉原子碰撞发生彭宁电离与转荷过程是该激光的主要激发过程.这种激光器可以连续运转.     

氦辐射线吸收谱等效宽度的理论分析

为了实现激光雷达对热层氦浓度的探测,本文理论计算了高斯线型、洛伦兹线型及佛克脱线型下亚稳态氦1083 nm辐射线吸收谱的等效宽度,结果表明佛克脱线型包含其他展宽机制信息,是最接近实际的光谱线型;亚稳态氦1083 nm辐射线的等效宽度的数量级为10-4;在热层温度范围内,等效宽度随温度的变化近似成线性关系;且随着波长的减小,等效宽度会增大。对于388.9 nm和318.8 nm两条辐射线也进行了计算,得出的结论与上述结论相似。此计算对于实现激光雷达对热层氦浓度的探测具有一定的参考意义。     

OMA—Ⅲ对He—MIP的光谱诊断

用微波感偶等离子体(MIP)作为原子发射光谱的激发源的可行性和优越性已被大量实验所证实。由于氦具有高的电离电位和高能量、长寿命的亚稳态能级,因而用微波感偶氦等离子体(He-MIP)进行原子发射光谱分析实验有效率高,背景辐射光谱简单,在     

利用共振光压偏转原子束的方法测量原子束速度的分布

本文报道利用共振光压偏转原子束的方法测量原子束速度的分布.给出了理论分析与实验结果.     

共振光压作用下钠原子束的偏转

本文报导了钠原子束在共振光压作用下的偏转实验及对实验结果的初步分析。 这个实验的特点是利用两块平面镜间来回反射的激光束所形成的多个光场与通过平面镜间的原子束相互作用,使原子束产生偏转。我们使平面镜与原子束成11°角,而入射光与原子束垂直,这时反射光束与原子束成68°夹角。若将激光频率调谐在钠原子的D_2线共振频率上(λ_L=5890(?)),则垂直光束与钠原子共振,而反射光束由于多普勒频移,激光频率对于钠原子束的共振频率低300兆赫,因此反射光束不与原子束相互作用。在垂直光束的作用下,原子吸收光子在光的传播方向获得光子动量,而自发辐射各向同性,因而光子反冲动量平均为0。因     

Theoretical analysis of the equivalent width of the helium emission lines' absorption spectrum

为了实现激光雷达对热层氨浓度的探测,本文理论计算了高斯线型、洛伦兹线型及佛克脱线型下亚稳态氦1083 nm辐射线吸收谱的等效宽度,结果表明佛克脱线型包含其他展宽机制信息,是最接近实际的光谱线型;亚稳态氦1083 nm辐射线的等效宽度的数量级为10-4;在热层温度范围内,等效宽度随温度的变化近似成线性关系;且随着波长的减小,等效宽度会增大.对于388.9nm和318.8 nm两条辐射线也进行了计算,得出的结论与上述结论相似.此计算对于实现激光雷达对热层氨浓度的探测具有一定的参考意义.     

原子纳米光刻中双层光学掩膜的实现方法研究

利用原子光刻的方法制备纳米结构的光栅已经成为了一种较为成熟的工艺。通过原子与激光驻波场的相互作用,利用原子自生在势能场中的偶极力对原子的密度进行调制,从而得到所需要的光栅结构。利用此种工艺所制备的光栅相对于传统工艺来说具有精度高,光栅常数直接溯源于原子能级。希望能够通过对激光的改良来提升原子沉积结果。通过双层驻波场来提高原子沉积质量已经被多次提到。实验中利用几何光学的方法实现了所需要的新型激光驻波场。并对其汇聚,相干等特性进行了研究,取得了较为满意的结果。为利用双层驻波场来沉积原子打下了基础。     

Optimization of a UV Cu+ laser excited bypulse-longitudinal Ne-CuBr discharge

The discharge conditions for high average output power on four UV Cu⁺ lines at 248.6 252.9, 260.0, and 270.3 nm, in a nanosecond pulse-longitudinal Ne-CuBr discharge, have been investigated in two discharge tubes of different designs. A record average output power of 210 mW (and a peak pulse power of 1.7 W) on the 238.6-nm laser line, and of 270 mW for multiline operation has been obtained. An optical effect enhancing the 248.6-nm laser line power has been observed as the intensity of two Cu atom laser lines (510.6 and 578.2 nm) increases. It has been shown that the presence of Br atoms in the discharge leads to a fall of the Ne metastable density via Penning ionization and, hence, to a decrease of the Cu⁺ metastable density and an increase of the laser output     

Doppler line shape of atomic fluorescence excited by molecular photodissociation

A semiclassical treatment of the photodissociation of a diatomic molecule is developed. It is shown that the angular distribution of products will often be peaked parallel or perpendicular to the direction of the incident light beam. The form of the anisotropy is usually determined just by the orientation of the electronic transition dipole moment within the molecule and the polarization of the exciting light. From the angular distribution, the Doppler line shape of fluorescence emitted by an excited fragment atom is derived by averaging the geometrical factors over the translational velocity distribution of the parent molecules and the distributions in magnitude and angle of the recoil velocity of the excited atoms. A comparison is made with dissociative electron impact processes which show similar features. The photodissociation of NaI is treated in detail, and the factors influencing the fluorescence width are evaluated for possible optical maser systems in which the supply of excited atoms is generated by molecular dissociation.     

原子束在漫射光中的激光减速

报道了利用红移漫射光冷却原子的新机制。理论计算了二能级原子在这一光场中所受的辐射压力，在实验上观测到了钠原子束在负失谐漫射光中的减速。     

Interdependence of buffer gas pressure and optimum interpulse delay in a burst-mode copper halide laser

The variation of the laser output energy of a 100 pulse burst with interpulse delay has been studied for each of the copper halides CuCl, CuBr, and CuI as a function of the tube temperature and of the buffer gas pressure for helium and neon. The tube bore was 12 mm and the specific discharge energy was 3.8 mJ ċ cm^-3. For CuI, the optimum interpulse delay decreases with increase in tube temperature and with decrease in the buffer gas pressure. At each temperature and pressure the optimum interpulse delay is shorter for helium than for neon. Although the formation of the laser pulse is intimately connected with the mechanism of breakdown in the discharge tube, the effect of this mechanism on the optimum interpulse delay is small and the latter is determined mainly by the dissociation-recombination cycle of the copper halide. The increase in optimum interpulse delay with buffer gas pressure suggests that either collisions with halogen atoms or molecules or superelastic electron collisions are responsible for the decay of the population of the metastable copper atoms.     

用于增加三维磁光阱装载率的二维冷原子束系统

在原子干涉仪、原子陀螺仪等精密测量的领域中，最基本也是最重要的一步就获得冷原子，而当实验需要连续和高重复性的测量时，对于冷原子的装载就会要求有更快的速率。为了能更快的装载冷原子，就需要一束高通量、低速的冷原子束。在实验上实现了87Rb原子的二维冷却磁光阱（2D-MOT）的冷原子束，其对3D-MOT的装载率为2.8109 atoms/s。该系统基于87Rb原子2D-MOT+push beam方案，选择了红失谐为20 MHz功率为50 mW的两束入射冷却光，在冷却光入射到真空腔之前使用扩束系统将其光斑扩束成短轴为25 mm、长轴为75 mm的椭圆形光斑，在冷却光入射真空腔之后在真空腔的另一端用镀了四分之一波片膜的反射镜来得到对射的激光。     

A continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit

Experimental characteristics of a continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit are reported. Quartz laser tubes 1 m in length and 1.5 and 2.5 cm in diameter were employed to study the effects of the electrical circuit, lasant, and buffer gas on laser performance. Measured properties of the Blumlein circuit are compared with an analytic solution for an idealized circuit. Both CuCl and CuBr with neon and helium buffer gas were studied. A maximum average power of 12.5 W was obtained with a 1.5 nF capacitor charged to 8 kV and discharged at 31 kHz with CuCl and neon buffer gas at 0.7 kPa in a 2.5-cm-diam tube. A maximum efficiency of 0.72 percent was obtained at 9 W average power. Measurements of the radial distribution of the power in the laser beam and the variation of laser power at 510.6 and 578.2 nm with halide vapor density are also reported. Double and continuously pulsed laser characteristics are compared, and the role of copper metastable level atoms in limiting the laser pulse energy density is discussed.     

A hybrid laser-magnet trap for spin-polarized atoms

This paper presents a brief survey of theoretical issues related to a hybrid laser-magnet trap for neutral spin-polarized atoms. At low densities, such a trap might be used to address a number of fundamental questions, e.g. the interaction of an individual atom with an electromagnetic field, while at high densities it might be used for “containerless” preparation of bulk amounts of a new metastable form of matter, spin-polarized atoms. In particular, a discussion is presented of the feasibility and limitations of a trap based on a near-resonant CW TEM^*₀₁ (“doughnut mode”) laser beam, which provides trapping in two dimensions, and on a strong homogeneous solenoidal magnetic field (the axis of which is also the laser axis), which provides trapping in the third dimension.     

Saturation and discharge studies in the He-Cd laser

The results of experimental studies of the various saturation effects and of discharge processes that occur in He-Cd lasers are presented and interpreted. It was found that the laser output can be adequately described by means of the rate equations. Based on these rate equations and the experimental results, the output and configuration of the He-Cd laser may be optimized. An estimate of the transfer cross section between the helium metastable and the cadmium atom is also presented.