超冷铯分子0g-长程态的振转光谱研究

通过超冷铯原子光缔合制备激发态的超冷铯分子. 利用冷原子荧光频率调制技术获得了超冷铯分子第一激发态6S_1/2+6P_3/2离解限0_g^-长程态高分辨振转光谱, 计算得到0_g^- 长程态振动量子数从0到51的不同振动能级的转动常数, 和Daniel研究小组的理论结果符合得很好. 关键词： 超冷铯分子 光缔合 振转光谱     

Rydberg原子nS1/2→(n+1)S1/2双光子激发EIT-AT光谱

主要研究了热原子蒸气池中铯Rydberg原子nS_1/2→(n+1)S_1/2微波耦合的双光子光谱.铯原子基态(6S_1/2)、第一激发态(6P_3/2)、Rydberg态(69S_1/2)形成阶梯型三能级系统,弱探测光作用于基态到激发态6S_1/2→6P_3/2的跃迁,强耦合光则作用于6P_3/2→69S_1/2的Rydberg跃迁形成电磁感应透明(EIT)效应,实现对Rydberg原子的光学探测.频率fMW=11.735 GHz的微波场耦合69S_1/2→70S_1/2的Rydberg跃迁,形成微波双光子光谱.利用EIT-AT分裂光谱研究微波电场强度对双光子光谱的影响.研究表明:在强微波场作用时,EIT-AT分裂与微波场功率成正比,而弱微波场时的EIT-AT分裂与微波场功率成非线性依赖关系,理论计算与实验测量结果相一致.本文的研究对微波电场的精密测量具有一定的指导意义.     

Rydberg原子nS1/2→(n+1)S1/2双光子激发EIT-AT光谱

主要研究了热原子蒸气池中铯Rydberg原子nS_1/2→(n+1)S_1/2微波耦合的双光子光谱.铯原子基态(6S_1/2)、第一激发态(6P_3/2)、Rydberg态(69S_1/2)形成阶梯型三能级系统,弱探测光作用于基态到激发态6S_1/2→6P_3/2的跃迁,强耦合光则作用于6P_3/2→69S_1/2的Rydberg跃迁形成电磁感应透明(EIT)效应,实现对Rydberg原子的光学探测.频率fMW=11.735 GHz的微波场耦合69S_1/2→70S_1/2的Rydberg跃迁,形成微波双光子光谱.利用EIT-AT分裂光谱研究微波电场强度对双光子光谱的影响.研究表明:在强微波场作用时,EIT-AT分裂与微波场功率成正比,而弱微波场时的EIT-AT分裂与微波场功率成非线性依赖关系,理论计算与实验测量结果相一致.本文的研究对微波电场的精密测量具有一定的指导意义.     

铯原子气室中D2线泵浦探测光谱的实验观测

在铯原子气室中采用偏振方向相互垂直且同向传播的线偏泵浦光和探测光，研究了铯原子D2线的泵浦探测光谱。由于在6 S1/2 F=3 – 6 P3/2 F’=2 超精细跃迁中存在多个L型塞曼子能级结构，从而产生了电磁诱导透明导致的吸收减弱；而在6 S1/2 F=4 – 6 P3/2 F’=5 超精细跃迁中则观测到了电磁诱导吸收。通过改变泵浦光的失谐量，在电磁诱导透明形成的吸收减弱凹陷和电磁诱导吸收产生的吸收增强峰内部均观察到了反常的吸收信号反转。     

超低频调制光缔合光谱的实验研究

通过激光冷却技术在磁光阱中俘获原子数约107,温度约200 μK,直径约400 μm的超冷铯原子,利用超冷铯原子光缔合方法制备了激发态的超冷铯分子。实验研究了光缔合光不同扫描速率对铯分子振转光谱分辨率的影响,发现光缔合光扫描速率较慢时,铯分子振转光谱分辨率较高。通过高灵敏的雪崩光电探测器探测冷原子荧光,获得了超冷铯分子第一激发态6S_1/2+6P_3/2离解限0-_g长程态高分辨振转光谱。为了实现受控拉曼光缔合制备超冷基态分子,光缔合激光频率需要锁定在原子-分子共振跃迁线,对超冷原子光缔合光谱进行了超低频波长调制,通过改变调制幅度和调制频率获得最优化的一阶微分信号,将该信号反馈回激光器,实现闭合环路稳频,满足了受控拉曼光缔合制备振转能级可控的基态分子的实验要求,该工作对研究受限空间中的超冷原子分子具有很重要的意义。     

低He气压下Rb(5P3/2)激发态有效辐射率的计算与测量

计算和测量了Rb-He混合蒸气中Rb(5P3/2)共振能级的有效辐射率,使用单模半导体激光器(泵浦激光)将Rb原子激发至5P3/2态,另一调谐到5P3/2→7S1/2的单模激光束(检测激光)与泵浦束反平行通过样品池,并在池的直径方向平行移动,通过对检测激光束的吸收测定了激发态原子密度及其空间分布.由于辐射陷获存在,有效辐射率是自然辐射率与透射因子(发射的光子在探测区域内没有被吸收的平均概率,它与吸收截面及激发态原子密度和空间分布有关)的乘积.5P3/2原子密度及其空间分布结合5P3/2←5S1/2跃迁线的碰撞增宽计算了透射因子,从而得到了不同He气压下,Rb D2线的有效辐射率.从5P3/2→5S1/2跃迁线强度I780的测量,得到的不同He气压下有效辐射率的比值与理论计算得到的比值相符.     

49S里德堡态的射频双光子光谱

在室温铯原子蒸气池中, 由铯原子基态、激发态和里德堡态构建了阶梯型三能级系统, 研究了里德堡原子阶梯型三能级系统的电磁感应透明(EIT). 在实现电磁感应透明的基础上, 利用16.9 GHz的射频电场耦合相邻的原子里德堡态, 实现49S_1/2→47D_3/2的双光子跃迁, 测量了里德堡原子的射频双光子光谱, 观察到了电磁感应透明光谱的分裂, 进一步研究了电场强度对射频双光子光谱的影响. 利用里德堡原子的EIT效应可实现对射频电场幅值和极化的精密测量, 具有潜在的应用前景.     

超冷(36D5/2+6S1/2)里德伯分子的制备及其电偶极矩的测量

里德伯-基态分子由一个里德伯原子和一个基态原子组成,束缚机制是里德伯电子与基态原子的低能电子散射相互作用.理论上,通过低能电子散射Fermi赝势模型,数值计算了铯(36D_5/2+6S_1/2)里德伯-基态分子的绝热势能曲线,提取了里德伯分子的束缚能和平衡核间距等光谱参数.实验上,利用双光子光缔合技术成功制备了散射三重态(^T∑,Triplet)和散射单重态-三重态混合(^S,T∑,Mixed)形成的里德伯-基态分子,获得了里德伯分子的光缔合光谱,测量的势阱深度与理论计算结果相吻合.另外,以散射三重态为例,分析了里德伯分子的光缔合光谱在外加电场中的展宽现象,获得其平均永久电偶极矩|d|为(12.10±1.65) Debye ((4.76±0.65)ea₀),与理论计算结果保持一致.该研究为实验上制备D态里德伯-基态分子提供了可行的实验方案,对理解里德伯分子的光谱特性具有重要意义.     

NO2分子(A)2B2电子激发态荧光辐射寿命的实验研究

采用准分子激光泵浦的染料激光诱导的高分辨荧光技术,测定了NO2分子2B2电子激发态的荧光辐射寿命及其与激发波长、NO2分子气体压力之间的关系,结果表明荧光衰减曲线是单指数的,辐射寿命在20.44～72.53 μs之间变化,利用光谱涨落统计理论对(A)2B2电子态的反常长寿命进行了讨论.     

激光烧蚀Al热原子与CF4反应中C2的形成及其发光光谱研究

脉冲激光烧蚀金属平面铝靶产生的热原子与气相CF4碰撞反应中，在400—600nm之间观测到激发态C2分子的发光光谱，它们可归属为Swan带的d3Πg-a3Πu跃迁中Δv＝２，1，0，-1，-2五个振动序列（v'≤6）.光谱强度分析表明，C2激发态的振动温度达6340K左右.与激光烧蚀Al＋O2反应生成AlO的实验结果以及激光烧蚀Cu＋CF4的光谱比较，对比Al(2P1/2-2S1/2,3944nm）和C2的d—a跃迁（0—0）带带头（5165nm)的飞行时间轮廓，认为激发态的Al(2S1/2)原子通过 关键词： 激光烧蚀 发光光谱 C2分子     

Generation and characterization of the highest laser intensities (10(22) W/cm2)

We generated a record peak intensity of 0.7 x 10(22) W/cm2 by focusing a 45-TW laser beam with an f/0.6 off-axis paraboloid. The aberrations of the paraboloid and the low-energy reference laser beam were measured and corrected, and a focal spot size of 0.8 microm was achieved. It is shown that the peak intensity can be increased to 1.0 x 10(22) W/cm2 by correction of the wave front of a 45-TW beam relative to the reference beam. The phase and amplitude measurement provides for an efficient full characterization of the focal field.     

Optical pumping of a Ne(3P2) atom beam with a multimode laser

Stable optical pumping of a neon metastable atom beam is achieved using a multimode dye laser. The factors that give rise to this stability are discussed. The resultant polarized beam is suitable for the study of electron spin and orbital orientation dependences in a variety of metastable atom collision processes.     

(2+1)维光学孤子在饱和非线性介质中的模式特征

从非线性Schrdinger方程出发,应用数学解析的方法,详细讨论了在饱和非线性介质中(2+1)维空间光学孤子存在满足物理意义的自洽解的条件,给出数值计算所需要的边界条件。通过数值计算,给出了基模和一阶模在某一组参数下的部分模式的光场慢变包络、光强度的二维和三维分布的直观图形,以及相应能量(无量纲)。结果表明,孤子的存在不是任意的,而是依赖于一定的能量。当光脉冲能量不足以支持孤子的存在时,其解呈振荡形式,说明不存在孤子解。同时还给出介质的饱和参数、孤子在传播方向上的波矢k对孤子模式的影响等有意义的结论。     

Picosecond laser ablation of high-quality micro-grooves on CIGS (CuIn(1-x)Ga2Se x ) thin films

ABSTRACT

This paper presents a study of the effects of ablation direction, beam profile and outer environment on the width and morphology of micro-grooves ablated by a 10-ps, 532-nm laser with a changing range of fluences and scan speeds on 600?nm-thick CIGS (CuIn_(1-x)Ga₂Se _x ) thin films. Experiments show that rear-side ablation by picosecond laser with a flat top beam in water environment yields a larger groove width than normal front-side ablation with a Gaussian beam in air, which is attributed to different material removal mechanisms, uniform energy distribution and the refraction of laser in water. The heat-affected zone and irregular edges induced by the tearing effect are the main defects of groove morphology associated with front- and rear-side ablation processes, respectively. Our studies indicate that flat top beam ablation, in general, inhibits the over-ablation in the central region, thereby improving the uniformity of grooves, though it does not eliminate the heat-affected zone and irregularity of two edges. The straightness of groove edges is further improved with the flat top beam ablation carried out in a water environment, resulting from the action of the shock wave in water. Hence, the nearly perfect micro-grooves can be fabricated with rear-side flat top beam ablation under water, which are characterized by steep sidewalls, straight edges and intact glass substrate without cracks.     

连续激光辐照ZnSe/MgF2/K9滤光片的透射特性研究

 分析了连续激光辐照ZnSe/MgF₂/K9滤光片引起透射特性的变化。在室温条件下，用波长0.632 8μm激光作为探测光束，测量了1.06μm连续激光辐照ZnSe/MgF₂/K9滤光片温升引起薄膜折射率的改变，导致探测光束通过干涉滤光片后透过率的热致非线性变化。在光斑直径0.75mm条件下，测量了不同功率激光辐照ZnSe/MgF₂/K9滤光片引起温升随时间的变化。在激光功率30W，辐照时间2.52s条件下，实验观测到ZnSe/MgF₂/K9滤光片薄膜破坏温度约为90℃，辐照时间10s时干涉滤光片形成的薄膜龟裂形貌。     

Surface evolution and laser damage resistance of CO2 laser irradiated area of fused silica

A 10.6 μm CO₂ laser has been reported to effectively mitigate the laser damage growth of fused silica. Two zones of the laser irradiated area are defined in this work: the distorted zone and the laser affected zone. The parameters of the two zones are studied at different CO₂ laser beam sizes, irradiation times, and powers by microscopy, profilometry, and photoelastic method. The results show that the diameter of laser affected zone is almost completely determined by the laser beam size and the distorted zone is associated with the mitigation range of CO₂ laser beam. The diameter and depth of the distorted zone increase as the laser power and irradiation time increase. The depth grows exponentially depending on the irradiation time. The maximum residual stress discrepancy is located near the boundary of the laser affected zone. The laser damage resistance test results show that the distorted zone and the laser affected zone have a better damage resistance than the original substrate.     

利用双光缔合光谱技术直接测量超冷铯分子0u+(6S1/2+6P1/2)长程态的转动常数的实验研究

实验获得了超冷铯分子6S_1/2+6P_1/2离解限下0_u⁺长程态振动能级v=187的转动常数. 首先利用调制的荧光光谱技术获得了高分辨的转动量子数J=0–6的超冷铯分子纯转动光谱. 利用双光缔合光谱技术, 构建了高精度的频率参考信号, 进而得到了相邻转动能级间的频率间隔. 最后通过非刚性转子模型拟合得到了转动常数和离心畸变常数.     

连续波HF（DF）化学激光器采用非稳腔的光束质量测量

描述了测量连续波HF(DF)化学激光光束质量的装置。给出了在非稳腔上测得光束质量的结果。     

Cr~(2+):ZnSe全固态中红外激光器

建立了一种高质量、高效率全固态中红外激光系统,并对激光输出的效率、光束质量等指标进行了测试。首先,以二极管激光器为泵浦源,Tm~(3+):YAP晶体为增益介质,搭建了输出波长为1.97μm的近红外激光器。然后,以Tm~(3+):YAP激光器为泵浦源,自行开发研制的Cr~(2+):ZnSe单晶为增益介质,搭建了全固态中红外激光器。最后,测试了全固态中红外激光器的光束质量及激光器出光效率,并对谐振腔光效率的理论输出值与实际的激光器出光参数进行了对比。实验结果表明:此全固态中红外激光器的光光转换效率为17.2%,斜率效率为20%,在最高输出能量为3 W时的光束质量(M~2)在x和y方向分别为1.7和1.73,光束基本为圆形的高斯光斑。     

Atmospheric turbulence and numerical evaluation of bit error rate (BER) in free-space communication

Bit error rate (BER) is an important parameter in free-space optical (FSO) communication. This paper presents the numerical evaluation of BER by studying the propagation of an initial Gaussian laser beam through turbulent atmosphere. Beam scintillation, spreading and wandering were considered as the atmospheric turbulent effects on the laser beam degradation. Different turbulent conditions and laser beam characteristics were applied to the calculations. The results show that the BER can be influenced considerably by atmospheric turbulence. According to these results the laser beam size and wavelength have also significant effects in the BER values.