半导体激光器的最新进展及其应用现状

简述了半导体激光器的现状,详细介绍了半导体激光器在激光雷达、激光测距、激光引信、激光制导跟踪、激光瞄准和告警、激光模拟、激光通信和光纤通信、光纤陀螺以及国民经济等各个领域中的应用.     

The light microscope on its way from an analytical to a preparative tool

Light intensities of up to 10¹³ W/cm² can be generated by focusing light, particularly laser pulses, into a microscope. Such power densities can be used to cut, perforate, or fuse microscopic objects with submicrometre accuracy. Suitable light sources for such a ‘microbeam’ are nitrogen lasers with a working wavelength of 337 nm, frequency-multiplied Neodym YAG lasers (266 or 355 nm) or excimer lasers (308 nm). In combination with dye lasers, tunable microbeams covering the wavelength range from the ultraviolet to the infra-red can be constructed. Such laser microbeams can be used to modify microchip substrates. Micro-injection of materials into biological cells or fusion of selected cell pairs under total microscopic control is also possible. Using the same equipment, elongated biological objects can be microdissected with submicrometre precision, for example in attempts to isolate DNA from a specific region of the human genome. In addition to the use of high-power pulsed lasers, the light of a continuous-wave infra-red laser can be used for the transport of microscopic objects. There, light pressure and the inhomogeneity of the electric field in a light pulse are used to trap microscopic objects in the focused laser beam, using the beam as ultrafine non-mechanical tweezers. Unlike mechanical microtools the optical trap is gentle and absolutely sterile. A combined laser microbeam and optical trap (a microbeam-trap) converts the light microscope, which is usually regarded as an analytical instrument, into a universal preparative instrument that allows micromanipulation of microscopic objects without mechanical contact. In contrast to any other micromanipulator, the microbeam-trap can work in the depth of an object without opening it.     

激光器在数字散斑干涉系统中的应用

介绍了在数字散斑干涉系统中经常使用的激光器 :He- Ne激光器、半导体激光器和 LD泵浦的固体激光器 ,总结了这几种激光器在数字散斑干涉系统中的应用原理 ,对比了各自的优缺点 ,并提出了一种新的应用领域——在采用数字散斑干涉技术的机器人口型识别系统中 ,应用微片激光器作为光源 ,对该激光器作了分析介绍 ,讨论了它的特点。     

激光器使用的光学薄膜

介绍了近年来研制的激光器用光学薄膜元器件,内容涉及二极管泵浦激光器使用的光学薄膜、光参量振荡激光器使用的光学薄膜以及激光美容仪使用的光学薄膜。     

半导体泵浦固态紫外激光器

新一代的半导体泵浦固态紫外激光器能输出平均功率１Ｗ以上的３５５ｎｍ光，全固态设计，坚固耐用，使用简便灵活，在工业精细加工上有突出的优势。本文介绍了这一类新型激光器的优点及在电路板加工和医疗上的一些应用。     

Ceramic to metal joining by using 1064 nm pulsed and CW laser energy source

A novel joining method for ceramic and metallic layers is proposed using laser drilling and surface tension driven liquid metal filling. A high intensity laser beam irradiated a 500 μm thick ceramic filter, and the irradiated laser drilled the ceramic layer. The pulsed or CW laser transmitted through the ceramic layer irradiated the bottom metallic layer; the molten metallic layer then filled the drilled ceramic holes by the capillary force between the liquid metal and ceramic layer. As process variables, average laser power, pulse duration, and the number of pulses were used. The scattering optical properties were also studied for both green and red lasers. There was no significant difference between the colors and the estimated extinction coefficients were ?26.94 1/mm and ?28.42 1/mm for the green and red lasers, respectively.     

Laser ion source development at Holifield Radioactive Ion Beam Facility

This report describes the efforts made to develop a resonant-ionization laser ion source based on tunable Ti:sapphire lasers for nuclear physics and astrophysics research at Holifield Radioactive Ion Beam Facility. Three Ti:sapphire lasers have been upgraded with individual pump lasers to eliminate laser power losses due to synchronization delays. Ionization schemes for 14 elements have been obtained. Off-line studies show that the overall efficiency of the laser ion source can be as high as 40%. TaC surface coatings have been investigated for minimizing surface and bulk trapping of the atoms of interest.     

Automation of a Research Facility for Atomic Vapor Laser Isotope Separation

The problems of introducing automation into experimental studies required for the development of an atomic vapor laser isotope separation method are considered. The investigations are carried out at a facility consisting of a vacuum module and a set of wavelength-tunable dye lasers pumped with copper vapor lasers. The vacuum module contains an atomic beam source, a quadrupole mass spectrometer, and a luminescence detection system. The approaches used to stabilize the laser wavelength and to scan the laser wavelength with the simultaneous recording of the mass-spectrometer and luminescence signals in strong high-frequency electromagnetic fields accompanying the operation of copper vapor lasers are also considered. Examples of experimental results are presented.     

Upgrade of the resonance ionization laser ion source at ISOLDE on-line isotope separation facility: new lasers and new ion beams

The resonance ionization laser ion source (RILIS) produces beams for the majority of experiments at the ISOLDE on-line isotope separator. A substantial improvement in RILIS performance has been achieved through a series of upgrade steps: replacement of the copper vapor lasers by a Nd:YAG laser; replacement of the old homemade dye lasers by new commercial dye lasers; installation of a complementary Ti:Sapphire laser system. The combined dye and Ti:Sapphire laser system with harmonics is capable of generating beams at any wavelength in the range of 210-950 nm. In total, isotopes of 31 different elements have been selectively laser-ionized and separated at ISOLDE, including recently developed beams of samarium, praseodymium, polonium, and astatine.     

Numerical simulation of the nano-second pulsed laser ablation process based on the finite element thermal analysis

In this research, the nano-second pulsed laser ablation process is studied using the three dimensional finite element analysis (FEA). Unlike other pulsed lasers such as femto-second or pico-second lasers, the nano-second pulsed laser can be analyzed appropriately based on the heat conduction theory and material removal approximation caused by thermal evaporation. Various process parameters such as the number of shots, laser power and wavelength and pulse width of the incident laser may affect the ablation process and we performed the parametric study and compared the simulation result with pre-existing experimental research. Finally, tendency of the ablation process is estimated using the design of experiments (DOE) and the response surface methodology (RSM).     

Random-distributed feedback fiber lasers based on Rayleigh scattering

Single-mode optical fibers have been widely used in optical communications, and effective fiber lasers have been designed on the basis of active fibers with linear or ring cavities. In fiber lasers, the distance between the cavity mirrors can reach 270 km (the maximum length is determined by the linear attenuation and nonlinear dephasing of the waves). In 2009, random lasing was found in a long telecommunications fiber without any cavity: the positive distributed feedback required for lasing is due to Rayleigh scattering of light, and distributed amplification is provided by stimulated Raman scattering. Such a laser can be classified into the group of so-called random lasers, actively studied recently; the fiber geometry and the weakness of Rayleigh scattering provide much better output characteristics compared to the other types of random lasers. The lasing efficiency and beam quality of this laser are comparable to those of fiber lasers with a conventional cavity. At the same time, it has a number of unique features (unlimited length, and mode-free spectrum etc.), providing new physical phenomena and new opportunities for applications in telecommunications and sensor systems. The paper presents a review of recent results of studies in this area.     

Infrared multiple photon dissociation spectroscopy of ions in Penning traps

The ability of Paul and Penning traps to contain ions for time periods ranging from milliseconds to minutes allows the trapped ions to be subjected to laser irradiation for extended lengths of time. In this way, relatively low‐powered tunable infrared lasers can be used to induce ion fragmentation when a sufficient number of infrared photons are absorbed, a process known as infrared multiple photon dissociation (IRMPD). If ion fragmentation is monitored as a function of laser wavelength, a photodissociation action spectrum can be obtained. The development of widely tunable infrared laser sources, in particular free electron lasers (FELs) and optical parametric oscillators/amplifiers (OPO/As), now allows spectra of trapped ions to be obtained for the entire “chemically relevant” infrared spectral region. This review describes experiments in which tunable infrared lasers have been used to irradiate ions in Penning traps. Early studies which utilized tunable carbon dioxide lasers with a limited output range are first reviewed. More recent studies with either FEL or OPO/A irradiation sources are then covered. The ionic systems examined have ranged from small hydrocarbons to multiply charged proteins, and they are discussed in approximate order of increasing complexity. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:448–467, 2009     

808nm980nm半导体激光迭阵波长耦合技术

随着半导体激光器在工业、军事、核能等领域的广泛应用,单个半导体激光迭阵的光功率已经不能满足实际需求,这就要求将多个半导体激光器耦合成一束激光,可直接输出或者由光纤耦合输出,以提高半导体光源亮度及光束质量。文章通过采用波长耦合技术进行激光合束,将两种不同波长的半导体激光束通过非相干技术经波长耦合器件耦合输出以实现大功率高效率输出,便于满足工业加工需要。介绍了非相干耦合技术中波长耦合原理及关键技术,根据波长需要设计耦合器件,并自行设计采用光学系统对光束进行扩束聚焦,通过实验将808nm和980nm两半导体激光迭阵光束通过此技术进行合束, 最终实现更高功率输出,耦合效率70%,光斑大小为3×3mm2,目前国内没有对此项技术进行研究。     

小型化单横模单纵模激光二极管泵浦Nd∶YAG激光器

在需要利用光的相干性的场合,如倍频、光参量振荡、全息以及光束的相干合成等对激光器输出的线宽有严格的要求,这时就需要对纵模进行选择。介绍一种小型化单横模单纵模激光二极管泵浦Nd∶YAG激光器,单脉冲能量3.6mJ,重复频率200Hz,脉冲宽度16ns,单横模、单纵模运转。该激光器采用谐振反射器和腔内倾斜标准具对纵模进行选择,试验结果与理论计算比较吻合。该激光器可用作窄脉宽高能激光器的种子源。     

An Increase in the Energy Yield and Giant-Pulse Generation Efficiency in a Laser with Self-injection of the Initiating Radiation

Optical laser systems that ensure generation of giant pulses from a narrow-band initiating free-running oscillation upon change in the Qfactor of the laser cavity and (or) in the amplification factor in it are described. The result of experimental studies of the parameters of a giant-pulse radiation generated by this type of ruby lasers with electrooptical switching of a branched combined cavity are presented.     

外腔调谐的全固态Cr∶LiSAF激光器

由于调谐元件置于主腔外时,插入损耗影响小,可以扩展调谐范围,本文采用外腔棱镜和光栅调谐结构研制了全固态Cr∶LiSAF激光器。分析了外腔调谐结构的基本原理,分别选用棱镜和光栅作为调谐元件,研制了棱镜外腔调谐Cr∶LiSAF激光器和光栅外腔调谐Cr∶LiSAF激光器。分析对比了棱镜和光栅调谐的输出功率、光谱、调谐范围等特性以及镜片镀膜对输出特性的影响。进行了调谐实验,结果显示:选用棱镜作为外腔调谐元件时,在325mW的吸收泵浦功率下实现了785~985nm的调谐,输出功率最高达21mW。选用光栅作为调谐元件时,亦可实现785~985nm的调谐,最大输出功率为20mW,光谱的半峰全宽(FWHM)为0.12nm。得到的结果表明外腔全固态Cr∶LiSAF激光器可以实现窄线宽、宽谱调谐输出。     

腔内倍频准三能级与四能级激光器噪声特性的比较

利用同种激光晶体Nd∶YAG和同种倍频晶体LiB₃O₅(LBO)分别构成蓝光(473 nm)与绿光(532 nm)激光器并进行了噪声特性研究。分析了腔内倍频准三能级与四能级激光器噪声的不同机理。实验发现:在输出功率为50 mW的情况下,腔内倍频准三能级激光系统的倍频光噪声为120%,比腔内倍频四能级激光器噪声大得多,后者在输出功率为60 mW的情况下,激光噪声在5%以下。针对准三能级倍频激光器的这种特点,采用耦合微分方程组模型进行了分析。结果指出,问题的根源在于准三能级激光系统中具有较大的再吸收损耗,如果能够适当控制该损耗,准三能级激光系统的倍频噪声问题便会得以改善。     

A Laser with Self-injection of Initiating Radiation with an Increased Energy Yield and Giant-Pulse Generation Efficiency

Optical laser systems with the self-injection of initiating giant-pulse radiation in a linear combined cavity are described. The efficiency of the generation of highly coherent giant pulses in such lasers can be raised through an increase in the initiating radiation intensity. The radiation parameters of such a type of ruby lasers were studied experimentally under loss modulation of a low-Q-factor cavity with a bleachable filter and electrooptical switching of the generation channel to a cavity with a higher Qfactor and (or) a higher active-element gain and (or) with a higher degree of the filling of the cavity with the active medium.     

激光共振电离质谱实验中的光束定位及合束装置

本文介绍了一种在激光共振电离质谱 ( LRIMS)实验中 ,用于定位和合成脉冲激光束的实用装置。在此装置中 ,采用同步式电荷耦合器件 ( CCD)相机对强激光散射光斑和弱背景进行不等时曝光来获取离子源内部图像。此方法解决了由于激光散射光斑和背景光强相差太远 ,从而使得采用视频 CCD相机无法同时获取两者图像的问题。同时 ,采用了一种新的四象限探测器对光束进行精确合束     

Technique for measuring the beam shape of pulsed lasers

A simple technique for the measurement of the beam shape parameters of pulsed lasers, with just a single pulse of the laser is described. It involves the use of several beam dividers inclined at very small angles to the beam axis, reflecting the beam back to a screen or a phosphor placed near the exit of the laser. The reflected images are then photographed by a camera to yield the beam parameters.