26fs自锁模掺钛蓝宝石激光器

采用４ｍｍ长的Ｔｉ：Ａｌ２Ｏ３晶体及一对熔石英色散棱镜，在腔内未加硬边光阑等元件的情况下，获得了平均功率５６０Ｗ、中心波长７７４ｎｍ、宽度２６ｆｓ、谱宽２８ｎｍ的锁模激光脉冲，分析了锁模的条件和工作特性。     

平行光束平面的旋转方法

一对偏长菱形棱镜能旋转平行光束的平面和改变光束间隔,这种新的光学系统(见图)是阿麦斯(Ames)研究中心建立的.除了其它用途外,这种棱镜结构能使激光速度计中所用的平行激光束平面旋转.偏长菱形棱镜能使平行光束产生横向位移(见图).因此,利用一对这样的棱镜便能使两个平行光束的平面发生旋转.     

考虑一下ECI 4吧

我是贵刊的长期读者，较喜欢古典音乐和爵士乐。我的听音室面积约20ō，音箱靠短边摆放，房间做过简单吸音处理，本月新购入B＆W S805音箱一对，CD机打算沿用老款的音乐传真A3，在放大器的选择上遇到了难题。     

方解石激光分束棱镜的设计

激光分束棱镜,在精密人卫测距机激光发射器中,是一个重要的元件。它起着对单一脉冲选出——再生放大器——三级放大器之间的光束分离变换的联接作用;更是再生放大器工作的重要元件。本文从理论上详细的叙述了对棱镜的选材;以及如何选择入射方向;确定与入射面的关系等问题。使各向异性的方解石材料,在某一特定的光轴取向上,具有各向同性材料的特性。从而利用费涅耳公式和折射定律,对各个界面的反射率进行精确的计算,选出最佳设计角度。最后给出了设计结果。     

超简化完全对称型直流功率放大器

完全对称型放大器是直流放大器的第三代电路、最早应用于电子管直流放大器,后来才移植到晶体管直流放大器。该放大器的突出优点是用一对相同极性的放大器件工作于完全对称的放大状态,其输出级不但具有功率增益还具有电压增益。放大器的平衡性好,     

激光辐射发散角的全景测量仪

本仪器是专用于测量广角激光辐射发散度和目视功率按光束截面分布的指示仪器。利用角共振滤光片测量激光辐射的发散角。滤光片由两块玻璃棱镜组成，棱镜的对角边用空气隙分开。     

正交泊罗棱镜谐振腔激光器

本文提出了一般双45°LNQ开关平一平谐振腔激光器及激光放大器存在的问题;论述了为解决此问题采用直块KD·P调Q、正交棱镜谐振腔激光器的光路原理、优点以及研制该器件中解决的技术问题;介绍了该器件达到的技术指标.实验结果表明;该器件满足了电视激光组合系统对激光器的要求,可以代替该系统中现采用的激光放大器     

宽带可变增益放大器

本文叙述了用一对差动连接的晶体管作为基本放大器单元的自动增益控制宽带放大器,并提供一附加的晶体管线路,使得放大器的增益成为两晶体管直流偏置电流之比的函数。与两个偏流之比成正比的增益函数能使放大器的增益按双曲线或线性变化。此外,噪声分量以及输出直流分量的变化可通过从外加输入电流中减去一直流分量而实现最小化,该直流分量为放大器最小增益时的输入电流的直流分量减去其值为放大器增益函数的直流分量。     

Hi-Fi中坚力量--天逸AD-99合并式放大器

在长期品玩音响的过程中,我有一种体会：寻找一台素质全面的放大器的难度甚至超过寻找一对好的音箱。一套优秀的Hi-Fi系统,不仅需要有良好的平衡感与优美的音色,还要有出色的动态与震撼力,能够准确地表达音乐的弦律、节奏与氛围。于是,就算是寻找到了一对优秀的音箱,如果所搭配的放大器驱动力不强、动态不佳、高频特性不好,效果也会大打折扣。     

破坏全内反射(FTIR)Q开关

针对现存问题,研究了一种性能优良的新型Q开关,即一种破坏全内反射(FTIR)Q开关。它具有光效率高,插入损耗低,能承受大功率(1GMW/cm~2),脉宽为15～20ns,输出稳定,易于控制。描述了FTIR Q开关的结构及原理。FTIR Q开关由一对熔石英棱镜组成。一个棱镜A为全内反射元件,另一个为A＇叫破坏元件。A＇与A的界面间距d小于一个激光波长。棱镜A＇的背面贴有压电换能器。M_2是全反射介质膜片。当光由熔石英进入空气时,在入射角     

激光脉冲编码识别概率的研究

从固定重频脉冲,跳频脉冲及等差周期脉冲的编码特征入手,对3种编码进行了全面的分析,介绍了3种编码的不同之处,并从原理上说明了激光脉冲编码的识别机制:固定重频脉冲编码时序间隔固定,等差周期脉冲编码时序间隔递增,而跳频脉冲编码的时序间隔不固定且不相关,针对3种不同编码的时序特点,分别给出了不同的识别概率模型.     

啁啾高斯脉冲在光纤中传输的脉冲展宽研究

通过求解非线性薛定谔方程,研究了线性光纤中色散导致的具有初始频率啁啾的高斯脉冲展宽的详细物理过程。得到高斯脉冲在光纤中色散所致的脉冲展宽的特性,啁啾因子对脉冲展宽的影响,并讨论了光纤色散对不同宽度脉）中的影响,对色散补偿等技术的研究具有一定的参考价值。     

电磁脉冲在地表大气中的传播

利用传递函数的方法研究电磁脉冲在大气中的传播规律，通过数值计算比较了矩形脉冲在实际地表大气和真空中衰减的差别，对矩形脉冲和正弦波，不同上升、下降沿梯形脉冲的大气衰减特性也做了比较。数值结果表明，大气吸收衰减使脉冲传播的距离降低，由于大气对不同频率电磁波的吸收不一致，矩形脉冲、正弦波在大气中的衰减随距离交迭变化，具有不同频谱分布的脉冲在大气中传播也有差异。     

偏振模色散补偿的实验研究

实验研究了高斯脉冲在PMD系数为225Ps／km^1/2的光纤中传输,发现超高的偏振模色散引起脉冲分裂,并用基模的两正交偏振分量耦合走离解释了脉冲分裂的成因．用PSP法实验研究了超高PMD的补偿,使输入光脉冲的偏振态对准光纤的偏振主态,可以大大减弱光纤PMD对传输信号的影响。     

Laser ablation and micromachining with ultrashort laser pulses

The mechanisms of ultrashort-pulse laser ablation of materials are discussed, and the differences to that of long laser pulses are emphasized. Ultrashort laser pulses offer both high laser intensity and precise laser-induced breakdown threshold with reduced laser fluence. The ablation of materials with ultrashort pulses has a very limited heat-affected volume. The advantages of ultrashort laser pulses are applied in precision micromachining of various materials. Some femtosecond laser pulse micromachining results, including comparison with long pulses, are presented. Ultrashort-pulse laser micromachining may have a wide range of applications where micrometer and submicrometer feature sizes are required     

脉冲形状对半导体激光放大器用于啁啾补偿的影响

光脉冲经过增益饱和的行波半导体激光放大器后,由于放大器的自相位调制,使放大脉冲附加上频率啁啾。合适的附加啁啾不但能抵销入射脉冲的初始啁啾,而且还有可能借助简单的群速度延迟线对脉冲进行压缩。本文计算了不同形状的入射脉冲经光放大器放大后的输出脉冲形状及其附加的频率啁啾,分析了它们对光放大器用于啁啾补偿的影响。     

Generation and the characteristics of current pulses from alloyed-type low-conductivity bulk GaAs

Current pulses with frequencies in the vicinity of 1 kHz were observed in low-conductivity copper-doped GaAs. The coherent current pulses were obtained by applying an ac half-sinusoid voltage to low-conductivity bulk GaAs samples with indium ohmic contacts. The repetition rate increased as the applied voltage was increased. Illumination of the specimen surface or change in ambient temperature had a strong effect on the current pulses. The current pulses are due to ionization of deep levels and are compared to the microplasma pulses observed in Si and Ge p-n junctions.     

High Energy THz Pulse Generation by Tilted Pulse Front Excitation and Its Nonlinear Optical Applications

Generation of high energy THz pulses by tilted pulse front excitation is reviewed. The basic idea and the realized setups are described. Properties of THz pulses generated by using different pump lasers are summarized. Nonlinear optical effects induced by the high energy THz pulses were observed, such as nonlinear refraction, self-phase modulation, saturation of THz absorption, and free carrier generation. The main results on these phenomena are described. The possibility of using THz pulses as a quasi-dc field for increasing the cut-off frequency in high harmonic generation is analyzed. The THz generation setup used in recent experiments is analyzed and arrangements for achieving better THz beam quality and higher THz pulse energy are considered. Finally, some results of calculations indicating significantly increased generation efficiency of 0.2-THz pulses compared to generation efficiency of 1-THz pulses are presented.     

Pedestal suppression from compressed femtosecond pulses using anonlinear fiber loop mirror

The compression of higher order soliton pulses in dispersion decreasing fibers (DDF's) generates ultrashort fundamental soliton-like pulses accompanied by a broad low-intensity pedestal component. In this paper, we investigate the subsequent removal of the pedestal using a nonlinear optical fiber loop mirror (NOLM) to produce high-quality pulses. The influence of higher order effects such as stimulated Raman scattering and third-order fiber dispersion on the pedestal removal from ultrashort pulses are considered, and the effectiveness of using dispersion-flattened fiber within the loop is shown. The technique is experimentally demonstrated for 540-fs pulses generated by compression in DDF. In this case, high-quality pulses are produced by pedestal removal using a NOLM constructed from dispersion-shifted fiber     

Picosecond dynamics of a gain-switched InGaAsP laser

Optical pulses are observed, with subpicosecond resolution, from an InGaAsP laser driven with 17 ps wide electrical pulses. The temporal profile of these gain-switched pulses is analyzed to obtain the transient and steady-state injected carrier densities in the active layer for dc biases above and below threshold. Gain-switched pulses as short as 13 ps FWHM are presented, and empirical results are compared to computer simulations. The implications of these results to pulse code modulation at very high bit rates are also discussed.