Time resolved beam divergence from a copper vapor laser withunstable resonator

The temporal evolution of the far-field intensity distribution (and hence beam divergence) for the output of a CVL operating with both on-axis and off-axis unstable resonators is investigated in detail. The CVL output pulse consists of several temporally resolved components, where each successive component has lower divergence approaching the diffraction limit. A comprehensive model for the divergence of each temporal component from a CVL operating with a variety of unstable resonators is presented. In this model the resonator controls the output divergence by imposing geometric constraints on the propagation of spontaneous emission on repeated round-trips through the unstable resonator equivalent lensguide. Effects of resonator asymmetry and radial gain variations on the far-field intensity distribution (and hence divergence) are evaluated. Experimental measurements of the temporal evolution of output divergence from a CVL operating with both on-axis and off-axis unstable resonators and for a variety of excitation conditions are also presented. For CVL operation at high pulse repetition frequency the ASE at the start of the laser pulse has an annular profile. This annular gain distribution is found to modify the output far-field intensity distribution of the earlier temporal components of the laser pulse. For on-axis unstable resonators these components are found to have annular far-field intensity distributions, whereas for off-axis unstable resonators they have greatly reduced but anisotropic divergence     

有限束宽下超高斯光束经光栅对压缩的研究

利用有限束宽下入射脉冲通过光栅对压缩的理论模型,从脉冲光束的傅里叶角谱入手,分析了脉冲超高斯光束单次及两次通过光栅对时的变换特性,以及高阶色散对脉冲压缩的影响。结果表明,脉冲超高斯光束单次通过光栅对压缩器时,横向谱移动使得出射光束产生时间相关的空间移动而两次通过压缩器时则会消除此种影响。高阶色散不仅影响输出脉冲的时间特性同时还影响其空间特性,导致输出脉冲波形扭曲,产生时空畸变。     

基于离散正弦变换的单载波频分多址系统及其性能分析

为分析离散傅里叶变换(DFT)与离散正弦变换(DST)对单载波频分多址(SC-FDMA)系统某些性能的影响,提出了一种基于离散正弦变换的单载波频分多址系统。给出了基于DST的SC-FD-MA系统的结构框图,接着重点推导和分析了DST IFDMA和DSTLFDMA信号的时域表达式,最后讨论了系统的峰值平均功率比(PAPR)和不同脉冲成形滤波器的冲激响应。仿真结果表明,基于DST的SC-FDMA系统比传统的基于DFT的SC-FDMA系统和正交频分多址接入(OFDMA)系统有更好的比特误码率。此外,DST SC-FDMA信号的PAPR性能接近于DFT SC-FDMA且优于OFDMA。     

高稳定激光二极管抽运Nd:YLF再生放大器

设计并实现了一种放大纳秒激光脉冲的高稳定的激光二极管(LD)抽运Nd:YLF再生放大器.为了获得高稳定的输出,再生放大器工作在饱和状态.此时,再生放大器输出稳定性最好,而且注入激光脉冲能量波动引起的输出激光脉冲波动被抑制.由于增益饱和效应,再生放大器输出脉冲出现时域波形失真,附加后缀脉冲能够减弱时域波形失真.放大器工作波长1053 nm,工作频率1 Hz.输入240 pJ的3 ns方波激光脉冲,输出激光脉冲能量4.2 mJ,总增益大于107,不稳定度小于1%(均方根),方波扭曲1.33.为3 ns方波激光脉冲引入其本身幅度0.75倍的后缀脉冲,输出激光脉冲方波扭曲由1.33降至1.17.     

不同陡峭边沿的皮秒光脉冲经半导体光放大器后的时域特性分析

分析了具有不同徒峭程度边沿的皮秒光脉冲通过半导体光放大器后输出脉冲的时域特性，其中着重考虑了输出脉冲的峰值功率和脉冲宽度的变化。结果表明：输出脉冲的峰值功率、脉冲宽度与输入脉冲的峰值功率、输入脉冲边沿的徒峭程度以及半导体光放大器的偏置电流密切相关。     

半导体光放大器(SOA)皮秒增益和折射率非线性的数值模拟

从速率方程出发 ,采用分段模型对半导体光放大器 (SOA)的皮秒增益和折射率非线性进行了数值模拟 ,具体分析了注入光脉冲引起的载流子浓度的变化、输出光脉冲时域波形的畸变、注入光脉冲引起的增益和位相变化 ,以及输出光脉冲上的频率啁啾。     

Cr4:YAG被动调Q激光器脉冲波形数值模拟及优化

从Nd:YAG晶体Cr4+:YAG被动调Q激光耦合速率方程组出发,数值求解该方程组,获得了激光脉冲的波形。从能量分布和时间分布的角度分析了被动调Q激光脉冲波形的不对称性。定义了描述脉冲波形的对称因子并分析了其与饱和吸收体初始透过率和输出镜反射率的关系。提出了计算脉冲宽度的新方法,重新计算了在脉冲波形非对称条件下的脉冲宽度及其与饱和吸收体初始透过率和输出镜反射率的关系。提出了优化脉冲波形和脉宽的简便方法。     

宽频带激光脉冲放大的逆问题

采用脉冲分割模型,研究了宽频带激光脉冲放大的逆问题,即由所要求的输出激光脉冲时间、空间波形、光谱分布和能量密度,并给定放大器参数情况下,求输入激光脉冲时间波形、空间、光谱分布。有关结果对高功率激光放大系统的设计有应用意义。     

宽频带激光脉冲放大的逆问题

采用脉冲分割模型,研究了宽频带激光脉冲放大的逆问题,即由所要求的输出激光脉冲时间、空间波形、光谱分布和能量密度,并给定放大器参数情况下,求输入激光脉冲时间波形、空间、光谱分布。有关结果对高功率激光放大系统的设计有应用意义。     

全光纤结构的脉冲光纤放大器

结合双包层掺镱光纤(YDCF)和主振荡功率放大(MOPA)技术,利用熔融拉锥的光纤侧面耦合器,设计和实验研究了全光纤结构的脉冲光纤放大器。在不同重复频率时,通过放大脉冲激光的输出光谱,对输出脉冲激光中的剩余抽运光和受激拉曼散射光功率进行了修正;并研究了激光脉冲的时域特性,以及在脉冲放大过程中对输出激光脉冲宽度的压缩作用。获得输出放大脉冲激光的主要参数:峰值波长为1075 nm,脉冲宽度为18~300 ns,重复频率为5~20 kHz,峰值功率达9.87 kW,斜率效率达52.2%,光束质量M2=2.0。同时,制作完成了一台结构紧凑、全光纤结构的脉冲光纤放大器样机,其最大外形尺寸为370 mm×270 mm×90 mm。     

高单脉冲能量重复频率TEA CO2激光器

为了满足激光推进、光电对抗等应用领域的需要,研制了一台高单脉冲能量高重复频率新型TEA CO2激光器。采用紫外(UV)预电离双路Ernst石墨电极串并联放电结构、超薄水冷不变形镜折叠腔、双回路直冷式封闭循环流动系统和高压大电流快脉冲开关电源等技术,解决了高功率高压电容充电、高气压大体积均匀辉光放电、高气压高速均匀流场、激光谐振腔和高脉冲能量、高重复频率脉冲激光输出等技术难题。成功研制了一台最大脉冲激光能量92 J,重复频率35 Hz,激光输出发散角1.4 mrad,脉冲能量稳定性0.8％,平均功率大于3000 W的脉冲激光器。     

钛宝石再生放大器自由振荡特性的实验研究

报道了自行建立的一台钛宝石再生放大器,它将作为整套TW系统的首级放大装置,并通过实验研究了它在自由运转条件下的能量和时间工作特性：获得了10％的斜率效率;在45mJ泵浦下得到了4mJ的脉冲激光输出;脉冲建立时间稳定在350ns左右,重复频率为10Hz。这些性能指标初步验证了再生放大器的腔结构和光学布置的合理性,其稳定运转保证了将进行的种子注入和放大。     

Investigation of the characterstics of a mode-locked Nd:Glass laser with the aid of a picosecond streak camera

An infrared-sensitive streak camera, capable of resolving optical pulses of durations of ∼3 ps, has been used to analyze the temporal development of the individual picosecond pulses in a mode-locked pulse train. A progressive increase in the duration of the individual pulses throughout the pulse train is observed, the rate of increase in the pulse duration being an approximate quadratic function of the optical field. In addition, temporal analysis of the laser output signal, dispersively delayed with the aid of a grating pair, confirms the existence of phase-modulation effects during the development of the mode-locked pulse train.     

Cr4+:YAG被动调Q激光器脉冲波形数值模拟及优化

为了研究被动调Q激光器脉冲的波形对称特性,采用数值求解Nd:YAG晶体Cr4+:YAG被动调Q激光耦合速率方程组的方法,获得了激光脉冲的波形,绘制出了"脉冲对称因子"与饱和吸收体初始透过率和输出镜反射率的关系曲线图;并根据脉冲波形的不对称性,更精确地计算了脉冲宽度,及其与饱和吸收体初始透过率和输出镜反射率的关系.得到参数b=0.6时,脉冲波形对称;b=0.78时,脉宽最小的结论.结果表明,可以通过调整b参数来优化被动调Q脉冲波形对称性和脉宽.     

增益开关型四能级激光器的时间特性分析

从四能级系统的速率方程出发 ,结合实际的物理条件 ,针对极短脉冲 (10 ns)泵浦下增益开关型激光器的时间特性建立了一个简洁模型 ,得到了输出脉冲的建立时间和脉冲宽度与泵浦能量及能量密度之间的解析关系式 ,并结合实验分析了模型的合理性。     

Ultrashort pulse self-switching in coupled-semiconductortraveling-wave amplifiers

A study is made of the self-switching of picosecond pulses using an active nonlinear directional coupler formed by two semiconductor laser amplifiers. Self-phase modulation associated with gain saturation permits all-optical control of output pulses emerging from the amplifiers, but switching from the cross state to the bar state is limited to 50% of the output energy. The amplified output pulses may be switched with little temporal distortion while considerable red shift in the output pulse spectra may occur     

Estimating intensity fluctuations in high repetition rate pulse trains generated using the temporal Talbot effect

We derive the upper limit of the peak intensity fluctuations for high repetition rate pulse trains generated using the fractional temporal Talbot effect for pulse repetition rate multiplication. Our analysis is general, can be applied to any input pulse shape, and can be used as a design tool to determine the input pulsewidth that will minimize the output amplitude fluctuations for a given multiplication rate.     

All-Optical Discrete Sine Transform and Discrete Cosine Transform Based on Multimode Interference Couplers

In this letter, a novel method to realize all-optical discrete sine transform (DST) and discrete cosine transform (DCT) is proposed. The approach requires only one multimode interference (MMI) coupler and several phase shifters at the input and output ports. By properly arranging the length of the MMI coupler and adjusting the phase shifters, the DST can be directly realized all-optically. Meanwhile, the DCT is related to the DST with a simple formula. By changing the input phase and relabeling the output ports, it can also be realized on the MMI structure. The proposed methodology has no limit on the number of the inputs.      

毫秒级宽脉冲速调管发射机研究

介绍了一种毫秒级宽脉冲速调管发射机的系统组成及关键技术。根据国内外技术发展的现状及靶场测量雷达的要求,确定了发射机的系统设计方案。分析了调制组件输出叠加方案的调制器及绝缘栅双极型晶体管串接方案调制器的优缺点。论述了BOUNCER 补偿电路和多路电源分时补偿电路的原理,给出了仿真数据及测试结果,同时对两种发射机输出脉冲顶降补偿方案的优缺点进行了对比分析。最后对研制成功的毫秒级宽脉冲发射机进行了测试,测试结果表明:输出功率、波形、频谱均达到了设计指标的要求。