Multiple-wavelength vertical-cavity surface-emitting laser arrays with a record wavelength span

Multiple-wavelength vertical-cavity surface-emitting laser (VCSEL) arrays are fabricated using a modified patterned-substrate growth technique in a molecular beam epitaxy (MBE) system. We achieved a large lasing wavelength span of 62.7 nm and highly uniform threshold currents with an average of 2.16/spl plusmn/0.81 mA. High repeatibility of wavelength spacing between 15 arrays with sharp wavelength shift rate 117.14 nm/mm is achieved.     

The Beam Property of DCN Laser

In this paper the lasing modes and the propagation property of a CW DCN laser, which cavity is a 50 mm inner diameter with length of 3.4 m, were studied. The modes of 195 and 190 μm lines are well identified by the micrometer mount of the movable mirror in one end of the cavity. The beam profile is found to be qualitatively Gaussian in the far-field (Z > 4 m).     

大功率In(Ga)As/GaAs量子点激光器

利用分子束外延技术和 S- K生长模式 ,系统研究了 In As/Ga As材料体系应变自组装量子点的形成和演化 .研制出激射波长λ≈ 960 nm,条宽 1 0 0μm,腔长 80 0μm的 In( Ga) As/Ga As量子点激光器 :室温连续输出功率大于 3.5W,室温阈值电流密度 2 1 8A/cm2 ,0 .61 W室温连续工作寿命超过 3760小时     

高功率横流CO2激光横模随时间变化的测量

用激光光束分析仪实时在线测量了一台连续运转的高功率横流CO2激光器的激光横模,获得了较为完整的激光横模随时间的变化关系.测量结果表明,激光输出由两个分离的、非对称的高阶横模叠加组成("双模"),两横模中心相距约8 mm.形成"双模"的原因是串接式谐振腔的前腔和后腔两者的中心轴线不重合以及阴极铜管形变.横模随激光器运行时间的延长而逐步蜕化,呈更高阶和复杂化趋向.初步分析表明,横模的时间变化主要与激光器连续运转过程中腔内气体组分发生的变化有关.     

三毫米波喇曼自由电子激光器实验研究

研制出新型小周期波荡器，报道三毫米波拉曼自由电子激光器实验。采用Ｉｃｍ周期双绕螺旋线波荡器，在相同加速器能量下，自由电子激光输出波长由８ｍｍ缩短到３ｍｍ。输出功率为１ＭＷ，效率为０．６６％。     

Characterization and control of gamma and proton radiation effectson the performance of Nd:YAG and Nd:YLF lasers

The laser performance of Nd:YAG and Nd:YLF crystals longitudinally pumped at 800 mm was evaluated before and after exposure to ⁶⁰Co gamma rays and high energy (30-50 MeV) protons. Both forms of radiation created the same damage centers in the respective crystals, which reduced optimal output primarily by absorbing the laser emission. While the radiation induced loss at the lasing wavelength for high quality Nd:YAG reached a limiting value of ~0.015 cm^-1 at 100 krad exposure levels, the loss in Nd:YLF was significantly larger than in Nd:YAG for all comparable dosage levels, and did not appear to have a limiting value. Given the relatively short path lengths of the laser crystals that were tested, the loss could be overcome for both materials under pulse-pumped operation, demonstrating that certain Nd lasers can be effectively radiation hard by design. Additionally, for the first time, Cr³⁺ was codoped with Nd in YAG (with minimal Cr⁴⁺ formation) yielding a high performance material with a significantly reduced radiation susceptibility     

利用整体毛细管X光半会聚透镜会聚同步辐射

为了进一步开展基于整体毛细管X光半会聚透镜和同步辐射的微区X射线分析,利用整体毛细管X光半会聚透镜和超环面镜的组合会聚了同步辐射。在8 keV能量点,利用超环面镜,将面积为2.3 mm×26 mm,竖直发散度和水平发散度分别近似为0和1.1 mrad的同步辐射光束会聚为面积为0.9 mm×0.3 mm,水平和竖直发散度分别为1.4 mrad和0.1 mrad的束斑,然后利用整体毛细管X光半会聚透镜将束斑会聚成直径为21.4μm的微焦斑,该整体毛细管X光半会聚透镜对束斑的传输效率为7.9%,该透镜焦距和焦斑处单位面积上的强度(功率密度)增益分别为13.3 mm和59。     

0.6 THz三次谐波回旋管的研究

 太赫兹回旋管是一类基于电子回旋受激辐射机理的快波器件,同时也是目前最具发展前景的高功率太赫兹辐射源.本文根据回旋管的线性理论和自洽非线性理论对三次谐波、工作频率0.6 THz的回旋管进行了研究,重点讨论了引导中心分别为0mm的实心回旋电子注和0.315mm的空心回旋电子注的模式竞争.通过分析比较,发现工作在0.6THz 、三次谐波的众多模式中TE37模是一比较理想的工作模式,它不仅有相对较高的功率输出,而且还有相对较少的模式竞争.本文中的设计采用55kV/1.0A,电子注的速度横纵比为1.5,在工作磁场7.86T下,数值计算结果表明输出功率达4.73kW.     

Phase-conjugation property of one-photon pumped backward stimulatedemission from a lasing medium

Optical phase-conjugation properties of the backward stimulated radiation from a one-photon pumped lasing medium have been studied. The gain medium is a dye solution (pyrromethene 597 in ethanol) or the same dye doped poly(methyl methacrylate) (PMMA) rod pumped with ~7-ns and 532-nm laser pulses. A highly directional and phase-conjugate backward stimulated emission at ~573 nm wavelength could be obtained with a conversion efficiency of ~42% by using a 1-cm-long dye solution sample at the concentration level of d₀=0.000 15 mol/L. The spectral, temporal, output/input, and phase-conjugation properties of this backward stimulated emission are presented in detail. The induced aberration influence, which is much larger than the divergence angle of the input pump beam, can be basically removed by the backward stimulated emission; however, the fidelity of the near-field detail for the backward stimulated emission is relatively poor. A quasi-collinear holographic interaction model and a mathematical analysis are presented to explain the basic experimental results     

百瓦级1.2/1.5 μm双波长金刚石拉曼激光器（特邀）

具有高功率、高光束质量的双波长激光器在精密光谱、共振干涉测量和激光雷达等领域有着重要的应用。但是受到激光工作物质固有的光谱和增益特性制约,通过传统的粒子数反转激光器难以直接获得高功率的双波长激光输出,因此通常需要结合非线性光学频率变换技术将常规的单一波长高功率激光拓展至一个或若干个特殊波段。受激拉曼散射作为一种三阶非线性效应,具有频移大、自相位匹配和光束净化等优点,是实现高效率、高光束质量波长转换有效手段。利用具有宽光谱透过范围（>0.23 μm）、超高热导率（>2 000 W·m?1·K?1）和大拉曼频移（1 332 cm?1）等优异特性的金刚石晶体作为拉曼增益介质,通过外腔振荡结构实现了1 μm泵浦光直接向1.2 μm和1.5 μm双波长激光的高效转换,在最高稳态泵浦功率414 W的条件下获得了1.2 μm和1.5 μm功率分别为72 W和110 W的输出。该研究为实现高功率的双波长激光输出开辟了新的途径。     

Spatial beam oscillations in stripe lasers utilizing InAsSb/InAsSbP heterojunctions

Anomalously narrow, single-lobe and double-lobe beam directivity patterns in the plane of the p-n junction have been observed in lasers constructed from InAsSb/InAsSbP heterojunctions emitting at a wavelength of approximately 3.3 μm. Theoretical near-field and far-field radiation distributions for the laser emission of two beams oscillating across the stripe are obtained on the basis of new concepts of the lasing processes. The single-lobe directivity pattern is obtained for the emission of in-phase beams, and the double lobe is obtained for antiphase beams. Correspondence of the theory with experiment is established. Fiz. Tekh. Poluprovodn. 33, 1014–1019 (August 1999)     

Laser-diode bars based on AlGaAsP/GaAs heterostructures emitting at a wavelength of 850 nm

Two types of laser heterostructures, i.e., those without internal mechanical stress compensation, with AlGaAs-alloy emitter and waveguide layers (type 1), and laser heterostructures with stress compensation, with AlGaAsP emitter and waveguide layers (type 2) are grown by metal-organic chemical vapor deposition (MOCVD). Laser-diode bars 5 mm wide with a fill factor of 24%, emitting at a wavelength of 850 nm are fabricated. Their power parameters in the continuous-wave (cw) and pulsed lasing modes are studied. It is shown that type-2 laser diode bars exhibit better linearity of the light-current characteristics in the cw and pulsed lasing modes in comparison with laser diode bars based on the type-1 structure.     

高效率Nd：YVO_4激光器的特性研究

报道激光二极管泵浦的Ｎｄ：ＹＶＯ４激光器的激光特性研究。激光晶体Ｎｄ：ＹＶＯ４厚度为１ｍｍ，基横模（ＴＥＭ００模）输出功率为２７３ｍｗ，斜率效率为４１％。     

A novel Smith-Purcell free electron laser

An experiment on a novel Smith–Purcell free electron laser (FEL) is described in this paper. The FEL is driven by a relativistic sheet electron beam of middle energy. The high frequency system of the device is a quasi-optical resonator composed of a diffraction grating and a three-mirror reflector. Coherent radiation with a peak power of tens of kW at the 3 mm waveband is sucessfully detected from an experimental facility. The main experimental parameters are: sheet beam energy from 400 kV to 500 kV; pulse length of voltage 70 ns; pulse beam current 0.2 kA; synchronous guide magnetic field up to 1.2 T with 10 ms pulse length; and grating period 2.2 mm.     

OC-48 capable InGaAsN vertical cavity lasers

A selectively oxidised InGaAsN/GaAs three quantum well vertical cavity laser (VCSEL) demonstrated continuous wave (CW) lasing with a single-mode output power of 0.749 mW at 1266 nm. This is the first reported InGaAsN VCSEL capable of meeting the power and wavelength requirements for both OC-48 SR and OC-48 IR-1 compliant links. The VCSEL uses two low absorption n-type GaAs/AlGaAs distributed Brag reflectors and a tunnel junction to achieve current injection into the active region. A multimode version of the VCSEL had a output power of 1.43 mW at 1.26 μm. CW lasing continued up to temperatures as high as 107°C. The VCSEL material was grown by solid source molecular beam epitaxy with an RF nitrogen plasma source     

XeF2光解离波的空间传输对形成XeF(C-A)激光的影响

利用XeF2光解离波图像，测量了现有激光实验条件下的解离波半径及传输速度，解离波厚度为5～8mm，传输速度随泵浦时间的增加而减慢，平均速度约13km／s。选择四种不同的腔轴位置，腔轴距泵浦源表面的距离d分别为10、13、16、20mm，激光实验结果表明，XeF2光解离波的空间传输对XeF（C—A）激光的形成有影响，激光形成时间、脉宽均随腔轴远离泵浦源而增加；输出能量在腔轴取13mm处最大。     

Tests of a grazing-incidence ring resonator free-electron laser

The authors describe operational experience of the first free-electron laser (FEL) using a grazing-incidence ring resonator. The Boeing FEL optical cavity was changed from a simple concentric cavity using two spherical mirrors to a larger grazing-incidence ring resonator. Initial tests showed that poorly positioned ring focus and unreliable pointing alignment resulted in reduced and structured FEL output. Later efforts concentrated on improving the resonator alignment techniques and lowering the single-pass losses. FEL performance and reliability have significantly improved due to better ring alignment. The alignment procedure and recent lasing results are described. The effect the electron beam has on lasing is also discussed. Measurements are presented showing FEL temporal output and wavelength are sensitive to electron beam energy variation     

Changes induced in a ZnS:Cr-based electroluminescent waveguide structure by intrinsic near-infrared laser radiation

The causes of changes that occur in a thin-film electroluminescent metal-insulator-semiconductor-insulator-metal waveguide structure based on ZnS:Cr (Cr concentration of ～4 × 10²⁰ cm^?3) upon lasing (λ ≈ 2.6 μm) and that induce lasing cessation are studied. It is established that lasing ceases because of light-scattering inhomogeneities formed in the structure and, hence, optical losses enhance. The origin of the inhomogeneities and the causes of their formation are clarified by studying the surface topology and the crystal structure of constituent layers of the samples before and after lasing. The studies are performed by means of atomic force microscopy and X-ray radiography. It is shown that a substantial increase in the sizes of grains on the surface of the structure is the manifestation of changes induced in the ZnS:Cr film by recrystallization. Recrystallization is initiated by local heating by absorbed laser radiation in existing Cr clusters and quickened by a strong electric field (>1 MV cm^?1). The changes observed in the ZnS:Cr film are as follows: the textured growth of ZnS crystallites, an increase in the content of Cr clusters, and the appearance of some CrS and a rather high ZnO content. Some ways for improving the stability of lasing in the ZnS:Cr-based waveguide structures are proposed.     

Peano分形加载单极子辐射性能的研究

对有限地板尺寸和介质填充情况下Peano分形加载单极子天线的辐射特性进行了研究.利用HFSS分析了地板尺寸和填充介质材料对天线反射系数、辐射方向图和增益的影响.仿真表明:随着地板尺寸的减小,天线的阻抗带宽和增益明显减小,H面方向图变化不大,而E面方向图的半功率波束宽度增大,波束仰角减小;填充材料的介电常数过大会导致天线性能的恶化.在分析研究的基础上,设计并研制了地板尺寸为220mm×220mm的一阶和二阶Peano分形加载单极子天线.天线分别实现了45°和36°的波束仰角,50°和45°的半功率波束宽度.仿真与实测结果均表明凋节地板尺寸是控制Peano分形加载单极子天线E面半功率波束宽度和波束仰角的一种简单而有效的方法.     

Self‐Assembled InAs Quantum Dots on InP(001) for Long‐Wavelength Laser Applications

Self‐assembled InAs quantum dots (QDs) embedded in an InAlGaAs matrix were grown on an InP (001) using a solid‐source molecular beam epitaxy and investigated using transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. TEM images indicated that the QD formation was strongly dependent on the growth behaviors of group III elements during the deposition of InAlGaAs barriers. We achieved a lasing operation of around 1.5 µm at room temperature from uncoated QD lasers based on the InAlGaAs‐InAlAs material system on the InP (001). The lasing wavelengths of the ridge‐waveguide QD lasers were also dependent upon the cavity lengths due mainly to the gain required for the lasing operation.