Development of a chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research

A chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research is described. The laser provides a 1.6 ps duration pulse with approximately 7 J energy at a repetition rate of 0.1 Hz. In the power amplifier system, laser light is amplified in a two-step manner: The first step is image-relayed multipass amplification up to approximately 1 J with a 10 mm x 10 mm beam. The second step is double-pass amplification up to >10 J with a 10 mm x 90 mm beam. By using this laser system, the saturated amplification of the Ni-like Ag laser at a wavelength of 13.9 nm has been successfully demonstrated.     

油气混和状态真空抽气系统试验初步研究

根据系统抽真空要求,完成管路设计选型与抽空能力计算.针对混和型介质及系统防火防爆的特点,优先选用干式真空泵.通过搭建真空管路系统,针对不同抽速真空泵、不同管路长度、不同抽空容器、不同混和介质开展多组试验.试验结果分析表明,干式真空泵能够满足抽空要求:管路中最小管径的管路长度对抽真空时间有较大影响;在本次试验条件下,环境温度变化对抽空时间有一定影响.     

Detectable distance calculations for a visual navigation system using a scanning semiconductor laser with electronic pumping

Results of detectable distance calculations for a visual navigation system based on a scanning semiconductor laser with electronic pumping (SSLEP) are presented. A semiconductor crystal in the laser is pumped with an electron beam, which is scanned across the crystal in the television-frame scan mode. The navigation system forms three orientation sectors with radiation wavelengths λ=0.52, 0.57, and 0.63 μm. Herein, calculations of energetic characteristics of output radiation are performed for the navigation system described above. The calculations were performed using the Range software package, which considers microphysical and optical characteristics of aerosol and observation path geometry for the case of coastal environment. Finally, comparison of results of the calculations with data obtained in marine and flight experiments is presented. It is demonstrated that minor discrepancies between calculated and measured values of detectable distance are observed in the coastal haze at lower values of meteorological visibility range S(m). As S(m) increases, the discrepancies become significant.     

Design of a device for pumping a double-clad fiber laser with a laser-diode bar

Pumping rare-earth-doped double-clad fiber lasers with GaAlAs laser-diode bars typically requires one to transform a 1-cm-long one-dimensional linear array of tens of multimode laser-diode sources into atwo-dimensional oblong cross section that approximately matches the fiber's first cladding shape. I describe the design of a device, henceforth called a high-brightness geometric transformer, that uses a cylindrical microlens to image the laser-diode bar near field onto a linear array of soft-glass, thin-clad, rectangular fibers. In turn, the fibers output ends are arranged to form a stack that matches the required first cladding shape. For a typical laser-diode bar with a brightness of 25 mW·μm(-2)·sr(-1), the geometric transformer output brightness is 0.6 mW·μm(-2)·sr(-1), i.e., there is a 40× intermediate loss of brightness. If the output of the geometric transformer is used to pump a Nd-doped double-clad fiber laser, anoverall brightness gain of 340× can be achieved.     

High-aspect-ratio line focus for an x-ray laser by a deformable mirror

A high-aspect-ratio line focus is required on a plane target in x-ray laser experiments for obtaining a high gain-length product. Inherent wave-front aberrations in line-focusing optics, which consist of a cylindrical lens and a spherical lens, are discussed with respect to beam diameter. The nonuniformity of the linewidth that is due to the aberrations is also calculated by the ABCD matrix method. A deformable mirror of a continuous plate type with a diameter of 185 mm provides an adequate wave-front distribution for compensating for the wave-front aberration. The wave-front control by the deformable mirror realizes a fine linewidth of 25 mum and 18.2 mm long, corresponding to the aspect ratio of 728. The linewidth is three times the diffraction limit. The intensity distribution along the line focus is also improved.     

智能化激光显示系统的设计与研究

研制了一套由激光器,图形输入仪,控制计算机,驱动器,光学工作台及大屏幕等六个部分构成的激光显示系统。理论研究得出,大屏幕所显示图形上的任意点P,均存在一与之对应的振镜偏转角确定值,精确控制振镜的偏转角即可扫描到P点。实验表明,系统可成功实现诸如函数图形、光栅衍射图案、光网光柱及文字动画等多功能智能化激光视频图像的动态输出。     

Frequency-shifted optical feedback in a pumping laser diode dynamically amplified by a microchip laser

Compared with conventional optical heterodyne detection, laser optical feedback imaging (LOFI) allows for a several orders of magnitude higher intensity modulation contrast. The maximum contrast amplification is typically 10(3) for a diode laser in the gigahertz range and 10(6) for a microchip laser in the megahertz range. To take advantage of the wavelength tunability of a laser diode and of the lower resonant detection frequency of a microchip laser, we used LOFI modulation induced by the frequency-shifted optical feedback in a laser diode as a modulated pumping power for a microchip laser for resonant dynamic amplification. In this way, we were able to transfer the optical feedback sensitivity of the laser diode to the megahertz range. Application to telemetry is also reported.     

Solid-state laser pumping with a planar compound parabolic concentrator

A novel solid-state laser-pumping scheme is proposed that combines a reflective lamp chamber and a compound parabolic concentrator (CPC) as a light guide. The CPC is made of a transparent material of high refractive index, and light is guided by the total internal reflection, with drastically reduced reflection losses. Material is chosen so that the absorption losses are minimized in the pumping wavelength range. The lamp chamber is designed with the principles of nonimaging optics, which ensures that the radiation is efficiently transferred from the lamp to the input aperture of the CPC. The pumping efficiency was first estimated theoretically, which gave us enough justification for the more accurate calculations with ray tracing. Single as well as multiple pumping cavities are discussed. New pumping geometry results in significantly increased pumping efficiency compared with conventional geometries. Also the lamp and the laser rod are separated, leading to reduced thermal load. We found that the proposed pumping method is also applicable to diode-pumped lasers.     

Development of an ejector cooling system with thermal pumping effect

This paper presents a feasibility study of an ejector cooling system (ECS) that utilizes a multi-function generator (MFG) to eliminate the mechanical pump. The MFG serves as both a pump and a vapor generator. The MFG is designed based on the pressure equilibration between high and low pressures through heating and cooling process. In this design, an ECS that contains no moving components and is entirely powered by heat can be practicable. A prototype using refrigerant R141b as working fluid was constructed and tested in the present study. The experimental results showed that the system coefficient of performance (COP_o) was 0.218 and the cooling capacity was 0.786 kW at generating temperature (T_G) 90 °C, condensing temperature (T_C) 32.4 °C and evaporating temperature (T_E) 8.2 °C. While taking into account the extra heat needed for the MFG operation, the total coefficient of performance (COP_t) is 0.185. It is shown that a continuous operation for the generation of cooling effect in an ECS with MFG can be achieved. This cooling machine can be very reliable since there is no moving part.     

Solid-state laser pumping by light guides

What we believe to be novel pumping schemes for lamp-pumped solid-state lasers are proposed. Based on the refractive and total internal reflection principles, curved fused-silica light guides of rectangular cross sections are used to couple the pump radiation from an arc lamp into a laser crystal. The performances of light-guide pumping schemes are analyzed through a nonsequential ray-trace program and are compared to that of a single elliptical cavity. Improved pump radiation distribution around the laser crystal was registered. The light-guide cavities also permit tailoring the pump flux distribution within the active medium. A lamp-pumped Nd:YAG laser by a light-guide cavity was built and tested. An overall laser efficiency of 1.1% was measured.     

Availability assessment of a two-unit stand-by pumping system

The paper aims at assessing the availability of a critical pumping system of the Crude Distillation Unit of a refinery with recourse to the Markovian model. Actual field data on failure and the repair times have been collected and analyzed by fitting exponential distribution. Also a simulation model has been developed for assessing the system availability. The availabilities based on both the analytical and the simulation models have been compared. The simulation model has been used for predicting system availability for varying failure and the repair rates. The repair strategies for the increasing failure rate in order to attain the desired availability have also been discussed in the paper.     

高速激光雕刻机嵌入式控制系统开发

以ARM9和FPGA作为核心处理器,并以Windows CE.NET 5.0作为开发平台,采用了多线程技术实现各功能模块的并发处理,研制了一种基于嵌入式平台的高速激光雕刻控制系统.为实现能量补偿,设计了调节电路来调节激光器输出功率的大小.针对高速激光雕刻的特点,着重分析了一种改进型S曲线加减速控制方法,并将其应用于系统设计中.系统已经用于某类激光雕刻机,实现了高速高精度雕刻.     

High-resolution tunable spectrograph for x-ray laser linewidth measurements with a plane varied-line-spacing grating

We describe a spectrograph for x-ray laser linewidth measurements in the range 100-220 A. The design employs a plane varied-line-spacing grating operating in the convergent light produced by imaging of the entrance slit with a concave spherical mirror. By the appropriate choice of the linear term in the grating-spacing variation, two separate wavelengths can be focused at the same image distance. As a result all wavelengths within the range of interest are focused at or near the same distance. The spectrograph can be tuned by rotation of the grating to bring any wavelength within the range to the center of the focal plane, and the spectra are dispersed on a surface that is erect or practically flat and perpendicular to the principal ray. This allows the use of a planar detector. With a streak camera used as a detector, the instrument obtained time-resolved linewidth data on x-ray lasers with a resolving power of 1 x 10(4) to 2 x 10(4). This paper presents the design methods used to optimize the varied-line-spacing grating, the design of the tunable spectrograph, and the results from the instrument in operation.     

Diode laser based photoacoustic water vapor detection system for atmospheric research

A wavelength modulated, distributed feedback diode laser based photoacoustic water vapor mixing ratio measuring system for atmospheric research applications is presented. Laser modulation parameters were optimized either at 180 or 500 mbar total pressure to enhance the system's sensitivity for low or high pressures (upper troposphere/lower stratosphere or biosphere exchange layer), respectively. A wavelength locking method was developed that ensured sub-picometer absolute (5 x 10(-7) relative) wavelength stability of the laser while consuming minimum additional measurement time. At the calibration of the system, correction factors for the pressure- and temperature-dependence of the photoacoustic signal were determined, which were in turn applied to the calculation of the water vapor mixing ratio from the measured signal during the test operation of the system. The introduced features resulted in reliable, sub-ppm-level water vapor detection even under abrupt gas pressure or temperature variations typical in open atmospheric applications.     

On the theory of a plasma-beam superheterodyne free-electron laser with H-ubitron pumping

The scheme of a plasma-beam superheterodyne free-electron laser (PBSFEL) with H-ubitron pumping is analyzed and several possible variants of its practical implementation are considered. Some variants represent sources of highly monochromatic signals, while the other generate signals with a rather broad spectrum. The increment of wave growth in PBSFELs is estimated and it is established that, under otherwise equal conditions, these FELs are characterized by much greater gain increments than the equivalent two-stream devices. The proposed PBSFELs have good prospects as sources of high-power electromagnetic radiation in the millimeter wavelength range.     

An electrochemical pumping system for on-chip gradient generation

Within the context of microfluidic systems, it has been difficult to devise pumping systems that can deliver adequate flow rates at high pressure for applications such as HPLC. An on-chip electrochemical pumping system based on electrolysis that offers certain advantages over designs that utilize electroosmotic driven flow has been fabricated and tested. The pump was fabricated on both silicon and glass substrates using photolithography. The electrolysis electrodes were formed from either platinum or gold, and SU8, an epoxy-based photoresist, was used to form the pump chambers. A glass cover plate and a poly(dimethylsiloxane) (PDMS) gasket were used to seal the chambers. Filling of the chambers was accomplished by using a syringe to inject liquid via filling ports, which were later sealed using a glass cover plate. The current supplied to the electrodes controlled the rate of gas formation and, thus, the resulting fluid flow rate. At low backpressures, flow rates >1 microL/min have been demonstrated using <1 mW of power. Pumping at backpressures as high as 200 psi have been demonstrated, with 20 nL/min having been observed using <4 mW. By integrating two electrochemical pumps with a polymer electrospray nozzle, we have confirmed the successful generation of a solvent gradient via a mass spectrometer.