窄带滤光片精确波长激光器高频调制特性研究

采用窄带滤光片作为选频元件对精确波长激光器高频调制特性进行了小信号分析.优化设计了外腔长度,兼顾了激光器的阈值特性和工作稳定性;给出了适用于外腔情况的光子寿命表达式;讨论了外腔反射率、管芯与外腔耦合效率以及外腔长度对光子寿命的影响.数值分析结果表明该类型激光器的调制响应特性主要取决于等效光子寿命,受偏置电流影响不大.当外腔反射率为72%,管芯与外腔耦合效率为80%,等效外腔长度为9.7 mm时,光子寿命为100 ps,激光器的调制带宽约为2 GHz,适合于以太网无源光网络中波分多址技术应用的需要.     

轻小型光子计数激光测距技术

为实现轻小型光子计数测距仪,利用905nm激光二极管（LD）以及硅基单光子探测器（SPAD）搭建了试验系统,通过外场测距试验研究了905nm激光二极管用于光子计数测距的测距性能。结果表明：905nm激光二极管由于其具有体积小、功率高的特点,同时硅基单光子探测器在905nm波段具有较高的响应率,基于以上两点,通过激光二极管以及小口径的接收望远镜能够实现远距离的光子计数激光测距。可见,激光二极管适合作为轻小型光子计数激光测距仪的光源,降低了系统的体积,有利于提高测距系统的集成度。     

Incoherent pulse Doppler lidar as the velocimeter system

This note reports a new type of incoherent pulse laser Doppler lidar velocimeter with iodine molecular filter as a frequency discriminator. Its transmitter subsystem applies a Nd:YAG pulse laser which is injected with a single longitudinal-mode diode pumped continuous seeder laser.The field experiment proved that this velocimeter measurement results are consistent with those measured by photoelectric velocimeter. Measurements of eight different velocities show that the standard deviation is 0.56 m/s, the range resolution is 3.75 m.     

基于脉冲注入调制的LD光功率-电流-电压特性测试系统

为精确测试半导体激光器(LD)的光功率-电流-电压(LIV)特性,提出一种基于脉冲注入调制的方法,并据此研制新型的LD脉冲测试系统.系统通过给被测LD注入脉冲宽度、周期及幅度连续可调的脉冲电流,采集恒功或恒流工作LD的工作电流、两端电压、背光电流和输出光功率等信息,绘制LD的LIV特性曲线,并以此推断LD的性能.采取低占空比的脉冲注入,有效抑制了LD有源区温度升高,保证了测试的可靠性和准确性.实验结果表明,脉冲电流的稳定度达到10-4,系统满足设计要求,其性能优于连续测试系统.     

脉冲驱动电源的设计与性能分析

采用低漂移高精度运算放大器进行恒流控制,时基电路NE555组成的单稳态触发器对脉冲宽度进行调制,设计了串联式脉冲半导体激光器驱动电源。该电源脉宽在0～100ms范围内可调,电流在0～3A范围内可调。通过精心选择元器件,获得了稳定的脉冲电流。另外该电源对激光二极管具有较好的保护功能,可用于激光点火系统。     

正弦调制自混合型半导体激光器光学传感的研究

研究正弦电流直接调制下 ,单纵模半导体激光器在外部物体的反馈作用时产生的自混合效应 ,利用这种自混合效应 ,对静止物体的距离进行非接触性的测量 .通过设定一参考距离 ,比较靶体与基准点处的拍频信号的最大频率值 ,简化了测量步骤 .分析测量误差与调制电流大小的关系 ,进而确定短距离测距的最佳实验条件 .     

激光二极管准直光源光学机械系统设计与调试

在数字音频唱机(CD)的开发方面,激光二极管(LD)由于具有一系列独特的优点,在科学与工程应用领域获得越来越广泛的应用.值得指出的是,LD激光器其光学和电气特性方面存在一些特别的问题,LD输出光束是:a.发散的;b.椭圆的;C.存在固有像散.环境温度的变化不仅影响其使用寿命,还会影响到其波长漂移和量子效率的变化.因此在实用时,必须对LD光束进行高质量准直,同时还应考虑系统的光能利用效率问题.为此,在研制高性能LD准直光源时,必须解决好以下四个问题:a.设计好准直物镜使其与激光二极管特性相匹配;b.设计合适的机械机构使LD与准直物镜集于一体,同时能够方便地进行精密光学对准,而且要具有一定的机械强度,使其能够承受一定的振动与冲击;C.研制有效的质量测试系统,以确保获得高质量的准直光束;d.研制安全可靠的LD驱动电源,以确保使用安全,延长寿命.     

半导体激光器驱动与控制系统的分析与设计

设计一种半导体激光器的驱动与控制系统, 能为半导体激光器提供高稳定度的驱动电流、 自动光功率控制和恒温控制, 提高了半导体激光器的使用寿命和输出波长的单一性.     

Nonlinear optics in the extreme ultraviolet

Nonlinear responses to an optical field are universal in nature but have been difficult to observe in the extreme ultraviolet (XUV) and soft X-ray regions owing to a lack of coherent intense light sources. High harmonic generation is a well-known nonlinear optical phenomenon and is now drawing much attention in attosecond pulse generation. For the application of high harmonics to nonlinear optics in the XUV and soft X-ray regime, optical pulses should have both large pulse energy and short pulse duration to achieve a high optical electric field. Here we show the generation of intense isolated pulses from a single harmonic (photon energy 27.9 eV) by using a sub-10-femtosecond blue laser pulse, producing a large dipole moment at the relatively low (ninth) harmonic order nonadiabatically. The XUV pulses with pulse durations of 950 attoseconds and 1.3 femtoseconds were characterized by an autocorrelation technique, based on two-photon above-threshold ionization of helium atoms. Because of the small cross-section for above-threshold ionization, such an autocorrelation measurement of XUV pulses with photon energy larger than the ionization energy of helium has not hitherto been demonstrated. The technique can be extended to the characterization of higher harmonics at shorter wavelengths.     

一种提高脉冲激光测距中时间测量精度的方法

脉冲激光测距的应用非常广泛,其中提高测距精度是该项技术的核心之一.为实现脉冲激光测距的高精度,提出一种时间间隔测量的方法.设计采用单片机控制时间测量芯片,对发射脉冲和返回脉冲信号延迟进行测量,同时利用时间测量芯片对测量结果进行自动校准,并采用定比例时点判别可减小信号变化对时点判别的影响.通过定点测量,结果表明该方法简化了器件设计,达到了较高的测距精度,最后分析了影响脉冲激光测距精度的误差的原因.     

半导体激光器稳恒功率控制系统的设计

设计一种半导体激光器的稳恒功率控制系统.该系统以3个高精度放大器OPA114,OPA602和OPA335为核心,采用滤波和慢启动电路,具有集成度高、元件少、性能稳定等优点;采用光功率负反馈控制,能为半导体激光器提供高稳定的、连续可调的驱动电流.实验结果表明,在该系统的驱动下,半导体激光器连续工作5 h,光功率稳定度可达0.048%,比开环时的稳定度提高了近5.5倍,达到设计要求.     

脉冲型阵列量子级联激光器驱动电源

设计并研制了一种高精度的可调节阵列量子级联(QC: Quantum Cascale)激光器驱动电源, 以用于中红外多气体检测系统。该系统运用时分复用的思想, 利用并联加串联的方式, 同时驱动多个QC激光器。在硬件方面, 以DSP F28335为主处理器, 采用压控恒流源的原理, 通过大功率半导体器件, 实现脉冲频率(1~10 kHz, 步进0.5 kHz)、 占空比(0.5%~40%, 步进0.5%)、 电流幅值(0~4 A, 步进0.1 A)连续可调的脉冲恒流源。在控制方案上, 采用模拟PI(Proportion Integral)控制算法, 通过两级模拟PI环节的双重反馈方式, 提高了驱动电流的准确性和稳定性。同时, 该系统还设计了电源滤波慢启动电路、 过流保护电路、 过压保护电路、 静电防护电路等, 防止QC激光器被瞬间大电流损坏, 以确保激光器的正常工作。经实验测试, 当设定脉冲电流幅值为2.0 A, 脉冲频率为5 kHz, 脉冲宽度为2 μs时, 输出脉冲电流幅值稳定度优于1.7×10^-3 A, 脉冲宽度稳定度优于2.4×10^-2μs, 脉冲上升时间小于11.9 ns, 脉冲下降时间小于9.6 ns。在同时驱动多个QC激光器长时间测试过程中, 驱动电流稳定, QC激光器发光稳定, 测试指标达到要求。     

Ultrafast generation of magnetic fields in a Schottky diode.

For the development of future magnetic data storage technologies, the ultrafast generation of local magnetic fields is essential. Subnanosecond excitation of the magnetic state has so far been achieved by launching current pulses into micro-coils and micro-striplines and by using high-energy electron beams. Local injection of a spin-polarized current through an all-metal junction has been proposed as an efficient method of switching magnetic elements, and experiments seem to confirm this. Spin injection has also been observed in hybrid ferromagnetic-semiconductor structures. Here we introduce a different scheme for the ultrafast generation of local magnetic fields in such a hybrid structure. The basis of our approach is to optically pump a Schottky diode with a focused, approximately 150-fs laser pulse. The laser pulse generates a current across the semiconductor-metal junction, which in turn gives rise to an in-plane magnetic field. This scheme combines the localization of current injection techniques with the speed of current generation at a Schottky barrier. Specific advantages include the ability to rapidly create local fields along any in-plane direction anywhere on the sample, the ability to scan the field over many magnetic elements and the ability to tune the magnitude of the field with the diode bias voltage.     

Probing molecular dynamics with attosecond resolution using correlated wave packet pairs

Spectroscopic measurements with increasingly higher time resolution are generally thought to require increasingly shorter laser pulses, as illustrated by the recent monitoring of the decay of core-excited krypton using attosecond photon pulses. However, an alternative approach to probing ultrafast dynamic processes might be provided by entanglement, which has improved the precision of quantum optical measurements. Here we use this approach to observe the motion of a D2+ vibrational wave packet formed during the multiphoton ionization of D2 over several femtoseconds with a precision of about 200 attoseconds and 0.05 ?ngstr?ms, by exploiting the correlation between the electronic and nuclear wave packets formed during the ionization event. An intense infrared laser field drives the electron wave packet, and electron recollision probes the nuclear motion. Our results show that laser pulse duration need not limit the time resolution of a spectroscopic measurement, provided the process studied involves the formation of correlated wave packets, one of which can be controlled; spatial resolution is likewise not limited to the focal spot size or laser wavelength.     

环境对单分子体系荧光光子统计性质的影响

利用近年所发展的产生函数（Generating Function）理论方法,研究了激光场和射频场共同驱动下单分子二能级体系发射荧光光子的统计性质.对在激光脉冲和射频脉冲场作用下单分子二能级体系的荧光光子发射特性进行了理论研究,并讨论了单分子二能级体系发射光子的控制等有关问题.     

基于回波模拟器的窄脉冲低震荡激光驱动设计

脉冲激光驱动电路的震荡会引起回波模拟的多目标、 虚景和半导体激光器损坏等问题。 针对这类问题, 从 RLC放电回路理论出发, 推导电流方程, 运用极值原理, 提出量化抑制震荡的方法。 根据实际某火控性能要 求, 运用所推公式确立了关键参数。 最后利用 MPSL01 型雪崩三极管作为高速开关器件设计电路, 获得了峰值电 流1 A, 脉宽23.2 ns 的窄脉冲电流, 且反向电流几乎为零。 采用 C86119E 型1 064 nm 半导体脉冲激光器作为光 源, 构成回波模拟器发射系统。 利用该单兵火控进行实际检测的结果表明, 驱动器性能稳定, 满足设计要求。     

75 mW robust single frequency Yb-doped DFB fiber Bragg grating laser

Incorporating the shielded method and post-processing method, a 75 mW single frequency Yb-doped DFB fiber laser was obtained with a 250 mW laser diode pump source at 978 nm. The threshold of the laser is 2 mW. The laser is single-polarization operation and the output power fluctuation is less than 0.2 mW in one hour when the pump power is 250 mW.     

飞秒激光与金属作用机理

对脉冲激光沉积过程中激光和金属作用的微观机制进行了深入分析.通过双温方程模拟得到飞秒激光作用金靶材温度随时间变化的图像.该图像反应出激光和金属表面及内部晶格作用特点.进一步分析得知,当晶格温度大于金属沸点时将会产生高能的等离子体.通过数值模拟找出了产生等离子体所需激光的能量阈值,这样能够帮助纳米材料的制备者选择激光,制备出优质的纳米薄膜.     

InP材料UV激光直接刻蚀研究

利用UV激光的光解剥离(APD)效应,对半导体材料InP进行了直接刻蚀研究,获得了良好的结果。采用波长为308nm,光脉冲宽度20ns的XeCl)准分子激光器,APD刻蚀的光能量密度阈值为390mJ/cm~2;与理论结果相比较,两者具有良好的一致性。同时给出了刻蚀深度与脉冲速率及脉冲时间的实验曲线。