克尔透镜锁模超短脉冲的时空往返模型

本文解决了由克尔透镜锁模的飞秒脉冲固体激光的时空模型中脉冲和波束形状的相互关系.根据随时间变化的脉冲的形状和KLM飞秒脉冲激光对于谐振腔中的空间光束参数建立了时空往返模型.     

研究微微秒变象管相机用的超短激光脉冲

本文概述了研制微微秒变像管相机对超短激光脉冲的形状、持续时间、脉冲形状内的能量分布、光谱成份等的要求。指出:矩形激光脉冲是检验微微秒变像管相机空间分辨率和时间分辨率最满意的脉冲及理想的光源。 利用被动锁模,自孔径选模,适当选择脉冲氙灯放电的网络参数,使在一定的时间内产生线性增加的增益系数α,确定在非线性位相过程开始产生的净增益⊿α,控制激光脉冲通过染料的次数m,维持腔内总振荡光子数N在激光阈值以上的增益曲线内不变,控制反转粒子数,使光脉冲前后沿每次得到相同的抽数,从而脉冲前后沿有相同的增益。由这种运转的激光输     

孤子激光器动态分析

孤子激光器可以产生优良形状的超短光脉冲,一般的孤子激光器是含有均匀线宽增益介质的主激光腔与含非线性介质的光纤附加腔构成。理论分析以此三项为依据;①激光锁模,②光孤子演化,③两腔耦合。先从主腔的主动锁模激光系统获得超短脉冲,然后进入附加腔,利用光纤中相位调制与色敬互相补偿作用形成孤子。这种光孤子脉冲比主腔锁模     

光通过色散介质反向散射的角度各向异性和脉冲动力学

本文给出均匀介质在光源方向散射的光脉冲时间形状的测量和模型计算的结果。对于具有激活同步模的氩激光脉冲研究了接近“后向”方向的散射动力学,氩激光脉冲在乳液微型粒子的水溶液中传播,研究是用光子计数时间相关的方法进行的。确立了反向散     

钛宝石激光器的多模式运转

在一台双光束泵浦的钛宝石激光器中实现了可调谐连续输出、独立自锁模、交叉锁模和多脉冲模运转式。分析了可调谐连续输出模式下两个激光腔的增益竞争,研究了飞秒和皮秒激光腔内的群速弥散、自相位调制、交叉相位调制以及自振幅调制。结果表明,可调谐连续输出模式下两个激光腔的输出主要取决于泵浦激光的功率,独立自锁模工作模式下,群速弥散和自相位调制决定了自锁模的稳定性;交叉锁模工作模式下,交叉相位调制是影响飞秒和皮秒脉冲之间同步性的主要因素。多脉冲工作模式下,脉冲自相关曲线的测量结果表明,飞秒脉冲仍然是单脉冲,而皮秒脉冲分裂为3个次脉冲。     

脉冲激光焊接参数研究

讨论了脉冲激光微型焊接中,对于激光的脉冲形状、激光脉冲宽度、激光通量密度等的选择,并给出了实验结果.     

重复频率脉冲激光纵模测量方法研究

提出了一种利用共焦球面扫描干涉仪对重复频率脉冲激光纵模结构进行测量的实验方法.该方法不仅能检测激光器是在单纵模还是多纵模下工作、计算待测激光的纵模间隔和谱线宽度,还能直接观测到各纵模的相对能量分布,测量精度高,结果直观,设备简单.实现了对1kHz以上重复频率脉冲激光纵模结构的测量,示波器上波形清晰稳定.利用该方法测量脉冲激光纵模结构在国内外文献中未见报道.     

钛宝石激光飞秒和皮秒脉冲的三种工作模式

在双光束泵浦的钛宝石激光器中,实现了飞秒和皮秒脉冲的独立自锁模、交叉锁模和多脉冲3种工作模式,分析了飞秒和皮秒激光腔内的群速弥散(GVD)、自相位调制(SPM)、交叉相位调制(XPM)、增益竞争和自振幅调制(SAM)。结果表明:独立自锁模工作模式下,GVD和SPM决定了自锁模激光脉冲的特性;交叉锁模工作模式下,飞秒和皮秒脉冲具有很高的同步性,脉冲间的抖动为517 fs,飞秒和皮秒激光腔的调谐范围分别为36nm和22 nm;多脉冲工作模式下,飞秒脉冲仍然是单脉冲,而皮秒脉冲分裂为3个次脉冲,间隔为426 fs。     

碰撞锁模环形染料激光器动力学过程的理论分析

根据碰撞锁模(CPM)激光器中两脉冲在可饱和吸收体中相干叠加建立瞬态粒子数分布光栅而加速脉冲压缩的机理,建立了其动力学过程的数学模型,针对实验中所使用的CPM激光器的参数进行了计算机模拟计算并对其结果进行了系统的理论分析。发现激光脉宽、两脉冲的对称性、脉冲本身的形状及激光输出的稳定性等与激光器中增益介质和可饱和吸收介质的相对位置、谐振腔的长度、泵浦速率的大小,线性损耗的大小以及染料浓度的高低等都相关,     

纳秒级宽带KrF激光时间脉冲整形

对纳秒级宽带KrF激光脉冲的时间整形进行了研究。采用受激布里渊散射(SBS)脉冲压缩KrF激光获得短脉冲,通过脉冲堆积获得KrF激光时间整形脉冲。利用激光放大器对整形脉冲进行放大,对KrF激光整形脉冲的形状影响较大。通过对放大前整形脉冲形状的调整,在放大后可以得到所需形状的整形脉冲,一次放大能量输出可达50 mJ,二次放大能量输出可达300 mJ。理论分析与实验结果一致。研究表明,短脉冲堆积和放大器放大的组合方案具有较强的整形能力。     

New bandwidth efficient overlapped pulse shape

A new pulse shape of duration twice the symbol interval is proposed for bandwidth efficient modulation. The proposed pulse shape is obtained by convolving a square pulse shape with a sinusoidal frequency shift keying (SFSK) pulse shape. The power spectral density (PSD) of a signal with the proposed pulse shape shows less power in spectral sidelobes than that of a signal with overlapped raised-cosine pulse shape     

脉冲激光点焊铝合金工艺特性研究

研究了几种特殊脉冲波形方式下，铝合金激光点焊焊点形态、尺寸的变化规律。实验结果表明，与矩形方波连续激光点焊相比，前期预制尖峰脉冲可以提高后期主脉冲阶段工件对激光能量的吸收效率，提高低功率下激光点焊的焊点稳定性;而后期的缓降脉冲波形能有效地减少焊点中的气孔和裂纹数量，但是增大了焊点表面的下塌量。缓升脉冲波形可以起到清理工件表面氧化膜的作用，减少焊点中氧化膜气孔的产生，并且能够减少焊点表面下塌量。结合缓升、缓降两种波形的优点，最后采用锯齿脉冲波形获得了无气孔、裂纹等缺陷的高质量焊点。     

Gain saturation characteristics of traveling-wave semiconductorlaser amplifiers in short optical pulse amplification

The gain saturation characteristics of traveling-wave semiconductor laser amplifiers (TWAs) are theoretically and experimentally investigated. In the amplification of an isolated pulse whose repetition period is short compared to the carrier lifetime, the gain saturation is related through the carrier lifetime to the gain saturation in CW amplification. When the output pulse energy is smaller than the saturation energy, short optical pulses can be amplified without pulse shape distortion, whereas high-energy pulses suffer from pulse shape distortion due to the temporal gain variation during the pulse radiation. FWHM pulse duration variation in amplification by TWAs depends on the input pulse shape. The pulse energy gain saturation was experimentally confirmed to be independent of pulse durations and to be determined only by the pulse energy. In extremely-high-repetition-rate pulse amplification, the saturation of the pulse energy gain is determined by the average signal power     

脉冲形状对三次谐波转换的影响分析

本文研究了基频光脉冲波形对三倍频转换效率的影响,对高斯脉冲和平顶脉冲的不同谐波转换特点作了详细分析,研究结果表明,当基频光脉冲形状偏离理想的平顶分布时,适当地降低二倍频转换效率,可提高三倍频转换效率。当基频光为高斯脉冲时,在3GW/cm2的输入条件下最佳的二倍频转换效率为56.8％,低于理论预计的66.7％。进一步的,计算了不同功率密度下,最佳二倍频转换效率与超高斯脉冲阶数的关系。     

Lateral electromagnetic waves and pulses on open microstrip

The propagation of lateral electromagnetic waves and pulses on microstrip is investigated. Interference patterns generated by the superposition of the lateral and direct waves along the air-substrate surface are shown. The field generated by the pulse excitation of a horizontal dipole on the air-substrate boundary is shown to consist of a lateral-wave pulse and a slower direct-wave pulse. Their differences in shape and decay rate are clarified. It is shown that the shape of a Gaussian pulse propagating along an open microstrip transmission line is closely related to the shape of the lateral electric-field pulse generated by a Gaussian current pulse in a dipole on the air-substrate boundary     

Isolation Rating of Ferrite Components at High Pulse Powers (Correspondence)

Any method used to measure the isolation provided by a ferrite component at high pulse powers must also consider the effect of possible distortion to the pulse shape owing to the nonlinear phenomena in ferrites. When such pulse shape distortion occurs, measurement methods based on average crystal current measurement or temperature rise in a calorimeter yield erroneous results. It is necessary that the method of measurement of isolation must be one which finds the difference between the maximum heights of the input and output pulses to the component irrespective of the pulse shape at the two ports.     

飞秒脉冲时空变换整形技术

飞秒激光脉冲通过时空变换技术将时域信息变换到空域,通过空域的处理再返回到时域,是实现飞秒激光脉冲整形、测量和控制的一项重要技术。在应用方面,可产生各种所需要的波形．已广泛应用在飞秒化学、信号处理、安全通信、生物学和医学成像等方面。介绍了飞秒时空变换脉冲整形的几种方法。     

Theory and methods for design of pulse shapes for broadcastteletext

The theoretical and practical engineering constraints, considerations, and methods for pulse shape design for North American broadcast teletext transmissions are described. The principles and concepts described are for broadcast over-the-air transmission, but they are also applicable to satellite and cable transmission of broadcast teletext signals. Overall objectives of pulse shape design are summarized. Basic constraints and considerations from the Nyquist theory are described. The practical and engineering constraints on teletext pulse shapes are discussed in detail. Pulse shape apportioning and specification are treated. A critical review is provided of the theory and design methods for teletext pulse shaping. A review of analytical and numerical approaches is given. Modelling and simulation approaches are described, including novel comprehensive model. Improved overall and transmitted pulse shapes are evaluated and their performance compared to that obtained with other common pulse shapes     

Optimal pulse shape for estimating positions of superimposed pulses

In this correspondence, we determine the optimal pulse shape for estimating positions of superimposed pulses by deriving the Cramer-Rao lower bound (CRLB) on the average estimation error variance and numerically optimizing it with respect to pulse shape. Our results show that a significant improvement in estimation error variance can be achieved relative to Gaussian and rectangular pulse shapes     

超高斯啁啾光脉冲在单模光纤中传输的演化行为

本文从激光脉冲在单模光纤中传输所满足的非线性薛定谔方程出发,通过分步傅里叶变换方法,数值研究了超高斯啁啾光脉冲在单模光纤中脉冲形状的演化.研究表明,超高斯脉冲在单模光纤中传输将经历一个从近平顶、多峰、最后到单峰的演变过程,且高阶色散将引起脉冲形状发生畸变;在GVD和SPM效应的共同作用下,无啁啾的超高斯脉冲在特定条件下将出现孤子演变,具有正啁啾的超高斯脉冲在传输的初始阶段,脉冲形状的变化非常剧烈,而由于负初始啁啾减弱了非线性与色散效应引起的频率啁啾,所以其脉冲波形的变化平缓一些.研究表明,SPM产生的啁啾对入射脉冲的初始啁啾有一定的补偿作用.