二极管泵浦高能激光研究进展和展望

高能激光广泛应用于材料加工、科学研究、空间碎片清除、军事应用等领域。二极管泵浦高能激光具有结构紧凑,系统简单、全电驱无限弹仓的特点,近年来,各类二极管泵浦高能激光围绕着同时实现高功率、高效率、高光束质量这一总目标发展迅速。详细综述了国内外高平均功率块状固体激光、高功率可见光波段激光、高峰值功率激光、高功率光纤激光、碱金属蒸气激光等二极管泵浦高能激光的研究进展,并对其发展趋势进行了展望。

对于影响PSD激光测距系统精度的因素分析

本系统对于影响PSD激光测距系统精度的相关因素进行系统分析,针对激光光功率、接受物镜的孔径以及接受物体的目标颜色等方面进行了讨论,最终通过实验数据对系统的测量精度进行了印证。

准连续Nd:YAG倍频高功率绿光激光器的研究

研制了高功率 Nd:YAG倍频绿光激光器 ,用类高斯光束分析了腔长对激光功率的影响 ,采用新型径向调整式光学镜片调整架 ,优化腔长为 390 nm,KTP晶体内腔倍频 ,并设置声光 Q开关 ,获得 5 32 nm绿光输出 2 0 W。

激光二极管列阵抽运Nd:YAG/LBO大功率蓝光激光器

报道了激光二极管列阵 (L DA)端面抽运全固体腔内倍频大功率蓝光激光技术的研究。采用复合 Nd:YAG晶体作为增益介质 ,并利用半导体致冷器 (TEC)对激光晶体的温度进行精密控制。倍频晶体采用 类临界相位匹配方式切割的 L BO晶体。谐振腔为 V型结构。根据大功率抽运条件下激光晶体热透镜效应严重 ,且热透镜的焦距会随着抽运功率的增大逐渐变短的特点 ,计算出最大抽运功率条件下激光晶体的热透镜焦距 ,依据此数据来优化谐振腔结构 ,使激光器实现最佳模式匹配和倍频效率 ,得到高效蓝光激光输出。在可吸收抽运功率为 1 8.5 W时 ,4 73nm蓝光激光输出功率为 1 .38W,抽运光 -倍频光的光 -光转换效率为 7.5 %。

激光二极管抽运Nd∶YVO_4/LBO腔内倍频5.3W连续波激光器

报道了激光二极管双向抽运Nd∶YVO4 晶体、LBO腔内倍频、最大输出功率为 5 .3W的连续波绿光激光器。采用LBO晶体Ⅰ类非临界相位匹配 (NCPM) ,温度调谐 ,当抽运光功率为 2 0W时 ,获得了 5 .3WTEM0 0 模 5 32nm绿光输出 ,光光转换效率达 2 6 .5 %。并对绿光模式及输出功率随LBO晶体温度的变化关系进行了测量 ,与理论结果符合较好。

Experimental study of the characteristics of novel microactuator based on optothermal expansion

A novel asymmetric optothermal microactuator was developed. A microactuator of 750μm length was machined by an excimer laser micmmachining system using single layer material. It had an asymmetric structure consisting of two thin expansion arms with different widths. A laser diode （660nm） was employed as the external power source to activate the microactuator. We introduced a charge coupled device （CCD）-combined optical microscope and a computer system to observe and capture the microactuator＇ s deflection and vibration. Experiments have been carried out to check the feasibility of deflection, and the data of deflection have been measured under different laser power as well as under different pulse frequency. The results show that the actuator can practically generate an obvious lateral deflection or vibration, the maximum could be larger than 20μm. Moreover, the deflection status of the microactuator could be controlled wirelessly or remotely by changing the laser power and its pulse frequency.

Physics of Power Semiconductor Streamer Laser

It is considered the mechanism of streamer discharge in the wide-gap semiconductors as a highly effective method of the laser excitation on the basis of representation about the phenomenon of light self-trapping of the discharge, providing their high propagation velocity down to v- 5 ×10^9 sm/s, the crystallographic orientation, filamentary character at thickness of the channel about 1 μm and absence of destructions of a crystal.

Influences of Uncaptured Electron on Energy Conversion of Photon Compton Scattering in High Power Laser-plasma

Using the single particle theory and the non-flexibility collision model of electron and photon, the influence of the uncaptured electrons on the energy conversion efficiency of multi-photon nonlinear Compton scattering in the extra stationary laser-plasma is investigated. It shows that in extra stationary laser-plasma,the uncaptured electrons make the Δω of the scattering frequency of the multi-photon Compton fall down with the increases of the incident radiation electron speed,the materials of the incident collision of electron and photon, and the number of the photons which work with the electrons at the same time. Under the modulation of the uncaptured electrons to the laser field, the energy conversion efficiency between electrons and photons will fall down with the increase of the electron incident radiation speed, using the low-power electrons for incident source, the loss can be efficiently reduced.

Analytical Expression of the Threshold Pump Power of Erbium－doped Fiber Lasers Pumped at 980nm and 1480nm Wavelengths

The rate equations,which is suitable to erbium-doped fiber lasers pumped at 980 nm and 1 480nm wavelengths respectively,are investigated,and analytical expressions of the threshold pump powers under two pump wavelengths are derived.As a result,some important parameters can be quantitatively specified.

A 155 Mbps laser diode driver with automatic power and extinction ratio control

An integrated laser diode driver(LDD) driving an edge-emitting laser diode was designed and fabricated by 0.35 μm BiCMOS technology. This paper proposes a scheme which combines the automatic power control loop and temperature com-pensation for modulation current in order to maintain constant extinction ratio and average optical power. To implement tem-perature compensation for modulation current,a novel circuit which generates a PTAT current by using the injecting base current of a bipolar transistor in saturation region,and alternates the amplifier feedback loop(closed or not) to control the state of the current path is presented. Simulation results showed that programmed by choice of external resistors,the IC can provide modu-lation current from 5 mA to 85 mA with temperature compensation adjustments and independent bias current from 4 mA to 100 mA. Optical test results showed that clear eye-diagrams can be obtained at 155 Mbps,with the output optical power being nearly constant,and the variation of extinction ratio being lower than 0.7 dB.

Study and development of high peak power short pulse Nd:YAG laser for peening applications

Because short pulse Nd:YAG laser of nanosecond pulse-width and high peak power has a unique capability to improve the mechanical properties of metal parts,a study on the development of high peak power short pulse from Nd:YAG laser along with its peening application has been performed.The design scheme of laser and the characteristic of laser beam transmission are presented and discussed.A pulse energy of 25 J with 15 ns pulse-width and a maximum peak power of 1660 k W laser system which use one oscillation and eight amplifiers has been achieved.Laser beam has a max divergence angle of 0.03 mrad,a pulse-to-pulse pulse-width stability of±0.1 ns,and the pulse-to-pulse energy stability factors of less than±2.8%.A low value of divergence means an easier modification of a nearly hat-top laser beam intensity profile and an easier transmission of laser beam.To evaluate the performance of the laser system,several metal materials are processed.Laser peening quality and efficiency are analyzed by using an optical microscope,a transmission electron microscope,and an X-ray diffraction device.The processing results show that the performance of this laser system is excellent.

Optimization of the cavity facet coating in high power GaN-based semiconductor laser diodes

A method to calculate the reflectivity of the coated cavity facet was proposed, and the distribution of the optical power near the two coated cavity facets was calculated for GaN-based laser diodes. A new design method for reducing the optical power at the two cavity facets without changing the output power of laser diodes was discussed, which is helpful to optimize the cavity facet coating and raise the threshold current at which catastrophic optical damage occurs.

A widely tunable fiber ring laser with closed loop control based on high-precision stepper motor

A tunable single-longitudinal mode erbium-doped fiber ring laser based on stepper motor and closed loop control is proposed and demonstrated. The system consists of an erbium-doped fiber （EDF）, a tunable fiber Bragg grating （FBG） filter and a wavelength detector. The characteristics of output laser, such as output power, power stability and 3-dB linewidth, are investigated in the operation range of I 531-1 569 nm. The repeated experimental results of the fiber laser show that the 3-dB linewidth is less than 17 ps, the side-mode suppression ratio （SMSR） is up to 60 dB, the outout Dower is up to 1.37 dBm. and the Dower variation is less than 0.61 dR

Analysis on spectral gain characteristics of PPMgLN based quasi-phase-matching optical parametric amplification

A deep understanding of the spectral gain characteristics of optical parametric oscillators (OPOs) and optical parametric amplifiers (OPAs) is important for a highly efficient optical parametric conversion. We numerically calculated the spectral gain characteristics of a quasi-phase-matching (QPM) parametric conversion process using the periodically poled 6% (mol/mol) MgO doped LiNbO3 (PPMgLN) as the nonlinear crystal. In the simulation we utilized the approach of a transformative matrix of the periodically poled nonlinear medium, which results from the small-signal approximation of three-wave mixed nonlinear equations. Numerical simulation results show that: (1) The full width at half maximum (FWHM) of the spectral gain of the parametric process becomes wider with the increase of parametric wavelength and reaches the maximum at degeneration; (2) The gain coefficient decreases gradually with the increase of parametric wavelength; (3) The spectral gain bandwidth decreases correspondingly with the increase of the nonlinear material length; (4) There exists an optimal parametric wavelength band, which is most suitable for the high gain parametric conversion when pumped by a laser source with a wide wavelength band, such as the high power fiber laser.