Electrically pumped lasing from CdSe quantum dots

Fabrication of a ZnSe-based laser diode which employs a fivefold CdSe quantum dot stack separated by ZnSSe spacer layers of high S content is reported. For the first time, electrically pumped room-temperature lasing from such quantum dots was obtained at a wavelength around 560.5 nm. The threshold current density is 7.5 kA/cm ²     

基于岛状多晶氧化锌薄膜的电泵浦紫外随机激光

光电子集成是当前光电技术和信息工程领域的新趋势和研究热点,其中光源集成化和工艺相容性已成为制约其进一步发展和应用的关键问题。报道了一种设计简单的、可直接集成在硅衬底上面的激子型激光二极管器件和工艺。基于岛状多晶氧化锌薄膜构建了一个金属/绝缘体/半导体（Au/MgO/ZnO MIS）异质结器件。利用Si衬底与ZnO外延层之间天然的大晶格失配,诱导ZnO薄膜表面形成了高度无序的多晶岛状纳米结构,从而在异质结激活层（ZnO/MgO界面区域）形成了高度无序的折射率随空间变化的散射介质。这极大增强了光学散射,有利于获得低阈值的随机激射。文中这种简单的光源器件结构设计和制备工艺提供了一种自下而上的实现氧化锌基集成光电子器件的新思路。     

管状激光介质的光学性质

针对管状激光介质的热透镜效应,提出“C1判据”和“热感应光线主轴”的观点;推导了二维光线矩阵和热透镜焦距;并指出提高光束质量的主要方法。     

Measurement of lasing performance and efficiency of e-beam pumped xenon chloride

Ane-beam pumped XeCl laser has been operated in mixtures of Ne/Xe/HCl and Ar/Xe/HCl. Careful measurement of energy deposited by thee-beam was made to allow accurate determination of intrinsic medium efficiency. Laser output in neon was found to agree well with the predictions of a kinetics model, and yielded efficiency of 5-6 percent. In an argon diluent, we have found efficiency as high as 8.0 percent.     

Properties of two-photon pumped cavity lasing in novel dye dopedsolid matrices

Two-photon pumped frequency upconversion cavity lasing at ~600 nm is accomplished in three types of dye-doped solid rods pumped with ~10 ns and 1.06-μm IR laser pulses. The dopant is a new dye, trans-4-[p-(N-ethyl-N-(hydroxyethyl)amino)styryl]-N-methylpyridinium tetraphenylborate, abbreviated as ASPT, which possesses a greater two-photon absorption cross section and stronger upconversion fluorescence emission than common commercial dyes (such as rhodamine). Three different materials were chosen as solid matrices: poly(2-hydroxyethyl methacrylate), VYCOR porous glass, and sol-gel glass. Using a Q-switched Nd:YAG pulse laser as the pump source, strong cavity lasing could be achieved in these three ASPT doped solid rods as well as in ASPT solution in a liquid cell. The spectral, temporal, and spatial characteristics of the cavity lasing output have been systematically investigated. The measured output-input characteristics, lasing lifetime, and damage threshold for the three different rods are presented     

One-, two-, and three-photon pumped lasing in a novel liquid dye salt system

We report the observation of one-, two-, and three-photon pumped lasing in the same medium, a novel liquid dye salt system when excited by pulsed 0.532-, 1.06-, and /spl sim/1.49-/spl mu/m coherent radiation pulses, respectively. Since the gain medium is a liquid and not a solution, it contains a significantly higher effective dye concentration and, therefore, is highly suitable for multiphoton pumped lasing and optical power limiting applications. The lasing spectra, temporal waveforms, near- and far-field intensity distributions, and output/input efficiency were measured under the conditions of one-, two-, and three-photon pump configurations.     

前、后向多抽运光纤喇曼放大器的增益特性分析

为了研究前向、后向多抽运光纤喇曼放大器的增益特性,在受激喇曼散射功率耦合方程组的基础上,采用龙格-库塔法结合打靶法分别计算了前、后向抽运功率、信号功率沿光纤的演化过程,并给出了抽运功率和信号功率的计算结果.结果表明,前向抽运系统中信号开始被放大,在最大处开始快速减小.低频抽运光的功率开始被放大的原因是由于抽运光之间的非线性相互作用引起的.后向抽运时信号开始被缓慢减小,然后在距离光纤末端处快速增加.这为以后喇曼光纤放大器的设计提供了重要的参考.     

前、后向多抽运光纤喇曼放大器的增益特性分析

为了研究前向、后向多抽运光纤喇曼放大器的增益特性,在受激喇曼散射功率耦合方程组的基础上,采用龙格-库塔法结合打靶法分别计算了前、后向抽运功率、信号功率沿光纤的演化过程,并给出了抽运功率和信号功率的计算结果。结果表明,前向抽运系统中信号开始被放大,在最大处开始快速减小。低频抽运光的功率开始被放大的原因是由于抽运光之间的非线性相互作用引起的。后向抽运时信号开始被缓慢减小,然后在距离光纤末端处快速增加。这为以后喇曼光纤放大器的设计提供了重要的参考。     

Cascade lasing of molecular HBr in the four micron region pumped by a Nd:YAG laser

Due to a narrow window of high atmospheric transmission near 4 /spl mu/m there is a great deal of interest for a scalable laser energy source in this spectral region. We propose a concept combining the advantages of solid-state and gas laser technology. It takes advantage of a coincidence of a Nd:YAG laser line and an overtone transition of the molecule HBr. Tuning a Q-switched Nd:YAG laser to 1.3391 /spl mu/m allows us to excite the v(0 /spl rarr/ 3), J(4 /spl rarr/ 5) vibrational-rotational transition of HBr. To stabilize the pump frequency, a diode laser locked to this HBr transition seeds the Nd:YAG laser. Once excited, HBr can potentially lase in three subsequent steps to the ground state, two of which were observed experimentally, emitting up to three photons in the 4-/spl mu/m region. We present theoretical and experimental results demonstrating the operational principle of this laser system. The comparison of experiment and theory suggests: 1) that intracavity CO/sub 2/ can force the system to lase on only those transitions that are within the atmospheric transmission window, and 2) the existence of amplified spontaneous emission driven by pure rotational transitions.     

半导体侧泵模块激光晶体内吸收光场分析

建立了半导体侧面泵浦模块中激光晶体的吸收光场分布模型,利用Matlab软件计算了吸收光场的归一化分布形貌,提出了两个重要参数:阵列切向位移量与径向角度偏离度。结果表明:当阵列切向位移量为0~0.5 mm时,晶体相对吸收强度、光场均匀性等参数基本不变;当该数值大于0.5 mm时,吸收强度急剧下降、光场不均匀性急剧增加;相比而言,径向角度偏移对晶体吸收光场分布的影响较小,总体上呈现随着该数值的增加,吸收强度减小、光场不均匀性增加。以上研究结论为目前半导体侧泵模块的研制生产提供了理论指导。     

Bragg reflection by a gain medium optically pumped in a grating geometry

The utilization of Bragg reflection caused by a grating-like pump intensity distribution in a laser-pumped laser amplifier is analyzed theoretically. In the amplifier, an incident laser beam is split into a transmitted and reflected beam, both of which are amplified. We explicitly take into account the interference between the transmitted and reflected beam and the effect of the interference on the saturated gain. We determine the reflective conversion efficiency of such an amplifier and show that if the gain grating is accompanied by a pump-heating-induced refractive-index grating, the reflective conversion efficiency may approach 100 percent.     

Frequency measurements of far infrared cw lasing lines in optically pumped CHCl2F

The wavelengths, frequencies, and relative polarizations of 15 FIR cw lasing lines obtained by optically pumping CHCl₂F with a cw CO₂ laser have been measured. The lines are in the wavelength range from 340.3 to 905.4 μm and were pumped by P- and R-branch laser lines in the 9 μm band of CO₂.     

利用光束后向散射提高激光跟踪发射精度方法

为提高激光跟踪发射系统激光发射指向精度,提出了一种通过测量发射激光后向散射光尖来修正激光发射指向误差的方法。在介绍系统光机结构及后向散射相关理论的基础上详细论述了光尖探测距离与视差的关系,根据天气情况和长期测量经验获得良好天气、中等天气和较差天气三种天气状况下光尖探测距离,进一步得出三种天气状况下视差修正量。在良好天气状况下,利用预定空间轨迹误差修正方式进行实验验证,对比光束后向散射法与靶板测量法所测得的激光发射指向精度,在预定的空间轨迹上两者测量误差为2.5,实验证明,利用光束后向散射法可以大大提高激光发射的指向精度。     

Threshold gain properties of lasing modes in ID disordered media optically pumped by femtosecond-lasing pulse

By numerically solving Maxwell's equations and rate equations,a comprehensive calculation on spectrum intensity and spectral widths of three localized modes via different pumping rates in one-dimension...     

纳秒脉冲激光抽运下的铯蒸气电离度研究

为了研究碱金属蒸气电离对半导体抽运碱金属激光器(DPAL)定标放大的影响, 采用适宜于短脉冲激光抽运源的光电流法来测量碱金属蒸气电离度, 并开展了铯蒸气电离度同激光抽运功率密度、碱金属池温度、抽运激光器重复频率之间关系的实验研究。结果表明, 在不考虑热效应的情况下, 即使抽运激光的功率密度高达3×108W/cm2、碱金属池温度150℃、氦气缓冲气压力9.33×104Pa条件下, 铯蒸气的电离度也仅仅达到1%左右; 在碱金属池温度从122℃升高至163℃的过程中, 相对于铯蒸气粒子数密度的显著增大, 铯蒸气电离度的变化非常小。该研究结果对于铯DPAL通过增加抽运激光功率密度和提高碱金属池温度进行定标放大具有非常积极的意义。     

二极管泵浦板条激光介质的二维温度和应力分布

用有限差分法对各种边界条件下二极管侧泵浦板条介质通光截面上的温度和应力二维分布作了数值计算。并对此作了分析,由此提出了适用于不同泵浦水平二极管泵浦板条激光器的冷却方案。     

The dispersion of the lasing medium and optimum length of the sample tube of OPFIRL

The dispersive characteristic of the optically pumped FIR laser (OPFIRL) system had been studied theoretically. It was found that the refractive index of the lasing medium was not a constant in the OPFIRL, and the approximate value n=1 must be corrected, otherwise, it will lead to a large error for theoretical calculation of the optimization of the operating parameters of the OPFIRL. The value of n as function of (Ip, Is, x, y, z, P) was calculated theoretically. The additional losses due to the energy exchange between the lasing system and the molecules populated in the energy levels except the appointed three-level system was estimated. The calculated optimum length of the sample tube of OPFIRL with the corrected theory was in pretty good agreement with the experimental result.     

二极管端泵浦连续激光器激活介质长度与透过率的优化

从准三能级系统的速率方程出发,推导出了二极管(LD)端泵浦连续工作端面泵浦固体激光器的速率方程,提出了计算连续LD端面泵浦激光器输出功率的方法,并表示成激活介质长度和透过率的函数,由此得到在泵浦功率一定情况时的优化设计步骤。数值计算结果与我们的实验结果和文献[3],[4]的实验数据符合甚好。     

Bragg微腔中非线性介质相位共轭波的增强效应

研究了由一维光子晶体构成的Bragg微腔（AB）^N（D）^2（BA）^N中三阶非线性光学介质（NLM）产生的相位共轭波的增强效应。当入射光波与Bragg腔模满足共振条件时,推导了其相位共轭波的增强因子。Bragg微腔中的三阶NLM产生的相位共轭波相对于该介质裸露时产生的相位共轭波具有明显增强,这主要是Bragg微腔对入射泵浦光产生了较大的共轭增强作用。理论分析和数值计算结果还表明,当入射光波与Bragg腔模满足共振条件且周期数N较大时,该结构可等效于由Bragg反射镜组成的Fabry-Perot（F-P）腔。     

Theory of backward second-harmonic and third-harmonic generationusing laser pulses in quasi-phase-matched second-order nonlinear medium

Recently, we have observed backward second-harmonic generation (SHG) using subpicosecond and nanosecond laser pulses in periodically poled lithium niobate crystals. The conversion efficiency in terms of energy density per pulse measured in the experiments agrees well with that based on our theory. In this paper, we present our theoretical investigation of this process in detail. Although the temporal behaviors of the second-harmonic radiation are determined by the same functions as those for the forward SHG, the amounts of pulse broadening and conversion efficiencies are quite different for the two configurations. In addition, we have investigated saturation of the conversion efficiencies. We have also considered effective third-harmonic generation based on cascaded second-order nonlinear processes. For a few optimized spatial periods of the domains, we have estimated the conversion efficiencies