准分子激光低抖动延时同步系统

准分子激光放大技术可将固体掺钛蓝宝石飞秒激光器通过频率转换后得到的小能量深紫外飞秒脉冲放大为大能量深紫外飞秒脉冲。为了满足准分子激光器与固体飞秒激光器之间同步工作的需要,设计了一种准分子激光低抖动延时同步系统。该系统采用现场可编程门阵列(FPGA)数字延时和可编程延时芯片延时相结合的方法,利用时间测量芯片实现对延时时间的闭环控制从而提高系统延时的稳定性,最终实现对外触发脉冲信号的精确延时。验证实验表明，该系统在1～100 Hz频率下运行稳定,输出触发脉冲信号延时范围为56 ns～2.4μs,理论延时步进为10 ps,抖动在±1 ns内,完全满足飞秒激光器与准分子激光器同步工作的需要。     

整形激光脉冲与激光探针同步技术

实现了应用于神光Ⅱ装置中的高精度整形激光脉冲与激光探针同步方案。在该方案中,激光探针经硅光导开关进行光电转换之后作为激光脉冲整形单元的触发信号,使激光脉冲整形单元,输出与激光探针同步的整形激光脉冲。为了降低由于触发信号不稳定引起的时间晃动,在光电转换之前放大激光探针,以调整激光脉冲整形单元触发信号的幅度。在神光Ⅱ装置中实现了整形激光脉冲与激光探针小于4.5 ps(均方根)的时间同步精度。     

脉冲激光微细加工曝光区温度的不接触测量

针对大功率脉冲激光微细加工区域工作激光对辐射测温的影响,提出在周期脉冲激光的间隙内提取温度信号的新方法,应用采样保持原理,研制相应的测量系统,通过温度定标,从A/D采样值直接读取温度值.结果表明,该温度测量系统能有效地消除工作激光对温度测量的干扰,准确地测量曝光区域的温度,在温度为500℃左右时,系统的温度分辨能力可达0.03℃,能满足激光扩散、激光合金等工艺要求.     

脉冲激光测距接收技术的研究

从脉冲激光测距的光电探测器人手,构建模型理论分析了漂移误差产生的原因,进一步给出了PIN管的光响应时间及其抖动大小与光照强度的近似函数关系．为稳定高效的探测反射激光脉冲信号和提高环境抗干扰能力,提出具有自动增益控制的自触发脉冲激光测距方案,不但减小脉冲信号上升沿引起的测距误差,而且也减小由于信号幅度变化带来的漂移误差影响．     

超快响应GaN半导体光导开关的研制

半导体光导开关(PCSS)利用半导体材料的高耐压、快速响应与高迁移率等特性,可产生大功率超窄脉冲信号。利用半绝缘GaN材料制备了异面斜对电极PCSS,通过去除芯片侧边金属化合物来减小暗态电阻,提升了PCSS暗态耐压并降低暗态漏电,采用绝缘导热封装提升器件的耐压与可靠性,研制了快拆式测试电路与夹具,实现储能、触发与低寄生同轴输出功能,提升了高频测试准确度与高频响应能力。搭建了高压宽带PCSS测试系统,测量开关线性工作特性,在5 kV偏置电压、触发激光脉冲波长为532 nm、能量为5 mJ下,GaN PCSS在50Ω负载上输出超快脉冲信号电压峰峰值大于2 kV,脉冲信号上升沿小于88 ps。     

基于CPLD的数字触发电路的设计

利用大规模可编程控制器(Complex Programmable Logic Device)CPLD，针对静止补偿器(STATCOM)对触发脉冲信号的要求．设计一种基于CPLD的正弦脉宽调制(SPWM)数字触发电路。正弦调制波的产生采用查表法，但仅将1／4周期的正弦波数据存入CPLD的内部硬件所构造的ROM中减少了系统的硬件开销．并具有脉冲封锁等功能，仿真结果证明了本设计的正确性。     

双单稳态触发器CC4528的特殊应用

CC4528是CMOS双单稳态集成触发电路,它有两个可再触发端A端与B端。若用脉冲上升沿触发,触发信号从A端输入,B端要接高电平;若用脉冲下降沿触发,触发信号从B端输入,A端要接低电平。CD是复位端,低电平有效。它有Q和Q两个互补输出端,产生一个精确的有较宽范围的输出脉冲,其宽度和精确度由外部时间元件R_x、C_x确定。图1是CC 4528的管脚排列。图2是逻辑图。其真值表如附表所示。     

对激光雷达特定的发射模块后向散射信号的调制和设计

测云激光雷达具有精度高和稳定性好的特点,是检测云高的有效途径.作为激光雷达系统的一个基本组成部分,脉冲二极管激光器(PLD)需要脉冲信号触发.对激光雷达的发射部分进行了研究,其中包括后向散射信噪比的仿真、脉冲二极管激光器的选择与触发电路、用于驱动综合光学系统的波长为905 nm 的PLD 的电路.触发电路激光脉冲具有可调功率和脉冲宽度功能.用Systemview 软件仿真设计,完成了PCB 版的制作.结果表明:脉冲的任何参数即触发脉冲宽度、上升沿、抖动等均可用于实验中,并具有低成本和使用方便的优点.该发光模块在测云激光雷达中运行良好.     

超高速硅开关

能够产生微微秒光脉冲的锁模振荡器进展很快,现在已经得到了稳定性和重复性很好的微微秒脉冲(功率稳定度±3％)。随着微微秒激光器的发展,现在正在研制能产生与这种光脉冲同步的各种超高速电脉冲开关元件。以前常用激光触发火花隙做开关元件。最近则研制并应用了触发管、雪崩晶体管和介质开关等。激光触发火花隙和触发管     

自动增益控制的自触发脉冲激光测距技术

文中提出了一种具有自动增益控制的自触发脉冲测距方案,不但减小脉冲信号上升沿 引起的测距误差,而且也减小由于信号幅度变化带来的漂移误差影响。实验结果表明:该激光脉冲测距系统在1m～10m的测距范围内,测距精度达到亚毫米级。     

Trimode ladar/radar transponder systems for tracking long range cooperative targets

Detection and tracking of cooperative airborne targets are very important for military and also for civilian purposes. Previous research has shown that detection and tracking LASER offer high precision but their operation range is limited to less than 40 km even in good visibility propagation conditions. For long operation ranges, high power and bulky RADAR are required which can be significantly reduced by using active transponders on the cooperative target. A trimode LADAR/RADAR/Transponder system is investigated providing optimum performances. A L band Radar with active transponder is operated for all weather long ranges up to Low Earth Orbit satellites. The L mode is switched to a Mm wave mode RADAR for operation distances lower than 350 km and to an accurate LASER mode for the final tracking steps.     

基于半导体光放大器的可调谐激光器

采用半导体光放大器设计实现了可调谐频域锁模激光器,可得到调谐范围宽、稳定性高的激光输出,基于半导体光放大器的可调谐激光器可用于光纤光栅传感系统,提高系统信噪比和解调精度,增强复用能力,改善系统性能.     

Short-pulse effects in a free-electron laser

The Free-Electron Laser for Infrared eXperiments (FELIX) offers a unique combination of short electron bunches and long wavelengths, i.e. a slippage parameter μ_c ranging up to 10. As a consequence, pronounced short-pulse effects can be observed. In this paper the experimental observation of two of these effects is discussed, namely the occurrence of limit-cycle oscillations and the feasibility of tuning of the micropulse duration. The stable limit-cycle oscillation of the macropulse power is due to a modulation of the optical micropulse shape. This is a consequence of a combination of high optical power and short pulses. The former causes synchrotron oscillations of the electrons and the effect is, therefore, closely related to spiking phenomena. The short-pulse nature of FELIX ensures that the oscillations do not evolve into the chaotic behavior normally associated with spiking and the sideband instability. Experimental results are compared with numerical simulations     

The accelerator for the Los Alamos free-electron laser--IV

The design parameters and performance of the accelerator used with the Los Alamos free-electron laser are described. Special emphasis is placed on those features of the accelerator that affect emittance, energy spread, and micropulse temporal shape.     

实用激光下水目标探测系统的设计分析

通过对搜索、测距、成像技术的分析,提出了一种较实用的激光水下目标探测系统模型以及工作时序,该系统机械结构相对紧凑,功能比较完善,充分发挥了激光探测的快速、准确、清晰、自动化程度较高的优势。     

Infrared free electron laser measurement of the photon drag effect in P-silicon

We report the use of FELIX (free electron laser for infrared experiments) to study photon drag in p-silicon over the wavelength range 25–80μm. Previous ‘spot’ measurements using a pulsed water vapour laser had indicated high response at 28 and 33μm associated with transitions within the valence band. These earlier results have been confirmed and the main futures of the extended photon drag spectrum are also explainable by reference to the valence band structure. A practical outcome of the experiment is the design of a subnanosecond response time detector to observe the 1GHz frequency micropulse output from FELIX.     

星载微脉冲光子计数激光雷达的探测性能仿真分析

星载微脉冲光子计数激光雷达能够实现对地面目标的高重频、多波束探测,有效提高了激光雷达在轨测量的采样密度和覆盖宽度,满足全球高效高精度测绘的需求。依据微脉冲光子计数激光雷达的工作原理,建立了基于多像元光电倍增管（PMT）的星载微脉冲光子计数激光雷达的探测仿真分析模型,并对典型探测过程进行了仿真分析。结果表明,多像元PMT像元数的增加能够明显降低激光雷达的首光子效应,提高测距精度;激光雷达的测距标准差随地形坡度增大而明显增大;对于复杂地形,增加像元数和回波光子数,光子计数点云能够更准确描述地形轮廓的分布特征。同时,机载飞行试验验证了在复杂地形条件下,多像元PMT能够显著增加有效回波光子计数点,准确有效地反映了被测地形的轮廓特征,实现复杂地形下的高精度光子计数测距,验证了仿真分析结果的正确性。     

A prebunched free electron laser

The narrow width of an rf-accelerated electron micropulse can be exploited to yield gain significantly higher than in the conventional FEL. If the micropulses are much shorter than the wavelength of the generated wave and the electrons are resonant with the FEL beat wave, then a low order prebunched FEL interaction results. All electrons lose energy to the wave     

AM mode-locking of a free-electron laser oscillator

The authors present experimental and theoretical studies of a mode-locked free-electron laser (FEL) oscillator. In the experiment the FEL uses a continuous electron beam and operates in the microwave regime. AM mode-locking is performed by modulating the attenuation of the FEL ring cavity by a PIN diode modulator. The modulation period is tuned to match the RF roundtrip time in the ring cavity. The experimental results show the evolution of a single radiation macropulse, consisting of narrow micropulses in synchrony with the sinusoidal locking signal. The micropulse period (~37 ns) equals the roundtrip time and the modulation period. The micropulse width (~5 ns) is limited by the FEL slippage time and by the dispersion in the waveguide ring cavity. The effect of the mode locking consisting in suppressing asynchronous oscillations is clearly observed in the experiment. A theoretical model of the AM mode-locked FEL oscillator operating in the small signal regime is presented. This model includes the slow time variation of the e-beam energy and waveguide dispersion. The theoretical analysis agrees well with the experimental results