用于泵浦固体激光器的大功率半导体激光材料及器件实用化研究

本课题采用分子束外延技术,生长高质量的大功率半导体激光器材料,并制备高性能的大功率半导体激光器器件,提供给八六三项目的其它课题,制做大功率半导体激光光纤耦合模块,为全固态绿、蓝光激光器系统提供高性能的泵浦源。 经过近5年的研究,在大功率半导体激光器材料生长和器件制备方面取得了很大进展。(1)研制出的808nm,大功率量子阱激光器材料阈值电流密度低(300～400A/cm~2),发光波长准确(808.7±3.0nm)均匀性比较高。(2)用它制备的808nm大功率量     

平面镜半导体光束整形的设计优化与光纤耦合

本文在光纤耦合理论分析的基础上,采用平面镜反射整形方法对半导体准直光束进行重排,提出了应用于半导体光束整形的整形器结构表达式.针对慢轴发散角较大引起整形次数增加和多次反射易损耗的特点,分析并优化平面镜的结构参数,设计了整形次数为13次的平面整形器,使得半导体激光器快、慢轴方向的光束实现光参数积均衡.通过对整个光学系统的模拟和实验,表明采用该方法能够实现条阵半导体激光耦合进入芯径200μm、数值孔径为0.22的光纤中,耦合效率接近50%.     

2 kW半导体激光焊接铝合金工艺研究

为实现半导体激光器对铝合金的焊接,将2 kW半导体激光器的光束进行整形,提高光束质量,光束亮度达到412.00 MW/cm².sterad,比整形前的光束亮度增加了7倍。然后采用整形的半导体激光器对1 mm厚度的6063铝合金进行拼接焊接实验,通过对焊接工艺参数激光功率、焊接速度、离焦量进行正交优化实验,焊缝接头最大抗拉强度为172.3 MPa,达到母材的85%,实现了半导体激光对铝合金的激光焊接目标。     

激光相干阵列成象雷达系统光束整形的研究

激光相干阵列成象雷达系统中本振光波前与信号光波前匹配与否直接影响系统的灵敏度和分辨力。采用共轭光栅合成技术对相干成象本振光束作整形处理，以适应探测器件列及合成输出满足最佳信噪比条件。     

浅析大功率半导体激光器面阵的光纤耦合技术

近年来,半导体激光阵列发展迅猛,但由于输出光束质量差,影响了其直接应用。因此,改善大功率半导体激光器的光束质量成为各国关注的焦点。本文在介绍光纤耦合技术的基础上,对大功率半导体激光器面阵光束整形方案进行了分析和研究。     

高功率掺铥光纤激光器及其在共振泵浦激光技术中的应用

与其他类型的光纤激光器相比,高功率掺铥光纤激光器具有安全性比较高、输出功率水平高以及可调谐范围比较宽等众多优点。由于高功率掺铥光纤激光器自身具有的这些优点,近几年,高功率掺铥光纤激光器的应用范围越来越广,发展潜力越来越大。本文将从掺铥光纤激光器的发展趋势及其应用领域、半导体激光器为泵浦源的前提下高功率掺铥光纤激光器的输出特性、窄线宽可调谐类型的高功率掺铥光纤激光器以及高功率掺铥光纤激光器在共振泵浦预案激光技术中的应用这四个方面进行详细阐述,以期推动高功率掺铥光纤激光器的发展。     

利用光纤和调制半导体激光的准直方法

本提出了一种新的激光光纤准直方法。利用光传播的平行性和直线性，光学准直技术被用于精密地建立几何参数的测量基准，在这些应用中，光束、处理电路的漂移、杂散光是影响测量精度的主要因素。为了消除这些影响，本利用调制半导体激光技术和光纤技术形成准直光束，四象限探测器进行探测，相敏检波技术对光电调制信号进行解调，所有的信号共享同一信号处理信道，且光束的调制频率远离杂散光的频率范围，激光光束漂移杂散光、电路漂移被抑制，在１ｍ范围获得了０．３μｍ的准直精度。     

基于光纤光栅外腔半导体激光器的2.5Gb/s波长转换实验

首次用光纤光纤光栅外腔半导体激光器的方法进行了2．5Gb/s的波长转换实验,将波长向上转换了5nm,得到了较清晰的眼图。该激光器采用标准的DIP－14低成本封装,该波长转换方法具有输出波长稳定,低啁啾的特点。     

大功率半导体激光器腔面镀膜的理论研究

从平面波假设出发推导了多层薄膜的特性矩阵，得到了膜系的反射率计算公式。研究了腔面反射率对大功率半导体激光器的外量子效率、阈值增益和输出功率比的影响，并给出了整个膜系反射率随膜层的光学厚度、折射率差及其层数的变化趋势。该模型对半导体激光器的腔面膜层设计具有实际的指导意义。     

940nm高功率列阵半导体激光器

利用分子束外延生长方法生长出ＩｎＧａＡｓ／ＧａＡｓ应变量子阱材料。利用该材料制作出的应变量子阱列阵半导体激光器准连续（５００μｓ,１００Ｈｚ）输出功率达到２７Ｗ（室温）,峰值波长为９３９￣９４１ｎｍ,并分析了影响列阵半导体激光器输出功率的因素。     

Beam quality of InGaAs ridge lasers at high output power

The nonlinear behavior of the light-current characteristic of single quantum well, graded-index-separateheterostructure ridge laser diodes emitting at 980 nm is investigated. We have measured the beam-quality factor |M|(2) as a function of the output power, under continuous-wave and transient conditions.The time constant associated with beam degradation under the transient condition suggests that the temperature profile in the cavity plays a significant role in the lateral guiding of the lasing modes. The two-dimensional heat equation is solved for the device, and the time-resolved thermally induced refractive-index profile is computed. There is excellent agreement between the time required to reach a steady index profile and that required to degrade the beam. The small beam astigmatism (typically 2 μm) measured under CW operating conditions in the linear regime indicates that the mode is essentially index guided, which permits simple quantitative modeling of the waveguide.     

Beam shaping design for coupling high power diode laser stack to fiber

A beam shaping technique that rearranges the beam for improving the beam symmetry and power density of a ten-bar high power diode laser stack is simulated considering a stripe mirror plate and a V-Stack mirror in the beam shaping system. In this technique, the beam of a high power diode laser stack is effectively coupled into a standard 550 μm core diameter and a NA=0.22 fiber. By this technique, compactness, higher efficiency, and lower cost production of the diode are possible.     

High-power semiconductor radiation sources based on 100-W diode laser bars for pumping solid-state lasers

High-power semiconductor radiation sources with a total optical output power of up to 5 kW and a power density of 400 W/cm² have been developed, representing a vertical stack of quasi-continuous pulsed (500 μs) 100-W diode laser bars. Based on such sources, a solid-state laser with an output radiation energy of up to 150 mJ has been created, which is intended for information systems, laser radars, spectrum analyzers, etc.     

Scaling up of a high average power dye laser amplifier and its new pumping designs

Scaling up of a high average power dye laser amplifier is discussed. Differences in the characteristics between a high average power dye laser amplifier with transverse pumping and longitudinal pumping are presented by a simple theory and simulations. The simulation results for dye laser amplifiers of 10-kW average output power show that longitudinal pumping is as efficient as transverse pumping with the potential of orders of magnitude lower dye flow rate. New pumping designs are also proposed for a dye laser amplifier aimed to achieve high gain with high efficiency to reduce the number of amplifier stages. Simulation results suggest that the new designs, in comparison with a conventional amplifier, can produce several orders of magnitude higher gain without decreasing the conversion efficiency.     

Locking bandwidth of optically injected Fabry-Perot semiconductor lasers for high injection strengths

The authors compare simulated results using a commercial software program with solutions of the rate equation (RE) and Fabry?Perot (FP) models of an optically injected FP semiconductor laser for high injection strengths (with injection ratios between the master and slave lasers above 0 dB). For linewidth enhancement factors (-factors) of 0 and 3, the locking bandwidth is compared with the RE model and in the case of an -factor of 0, the results are also compared with the FP model. It is found that the RE model for high injection strengths does not describe the locking bandwidth very well, whereas the FP model gives good agreement with our simulated results. Additionally, the longitudinal variation of optical power and electron concentration are shown for different injection strengths and different detuning values. For an a-factor of 3, the spatial variations of these properties become asymmetrical for higher injection strengths and with an increase in detuning, they are found to exhibit decreased fluctuations when the lower locking boundary is approached through the locking region. Therefore it is important to take spatial variation into account for high injection strengths.     

Applications and performance of high power lasers and in the battlefield

This paper reviews the status and applications of a defensive weapon based on high power lasers, in the battlefield. Laser weapon is a novel concept which utilizes high power laser beam to traverse the distance into incoming objects at a speed of light, and then, destroy or disable it. Various types of lasers and configurations will be discussed in this review including gas lasers, solid state lasers, fiber lasers and the free-electron laser. We will discuss various configurations such as airborne laser (ABL), diode pumped crystals and disk lasers as well as heat-capacity lasers. Recent applications of ultrafast solid state lasers for non-lethal or low collateral damage applications will be presented.