激光专业英语2讲解课件

*,*,单击此处编辑母版标题样式,*,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Laser,Specified English,20,11,年,8,月,Laser Specified English2011年8,1,训练课,变成我猜我猜我猜猜猜的节目了,训练课,2,本课程是,激光加工专业的必修课,。本课程的学习，目的在于帮助学生在专业学习和研究中更好地应用英语，以逐步达到能用英语较熟练地阅读本专业的文献资料及适应其他科技交流活动的需要。,本课程的教学基本要求:,学习常用,激光工程,英语词汇、术语；,掌握科技英语的特点；,提高运用英语从事,激光,工程相关的阅读、写作、会话的能力。,本课程是激光加工专业的必修课。本课程的学习，目的在于帮助学生,3,本课程由,二,个部分组成：,第一部分偏重于,激光,英语文章的,英汉翻译,第二部分偏重于,激光,英语文章的,汉英翻译,课程第一部分的目标：,帮助学生能用英语较熟练地阅读本专业的文献资料,在方法上，选择本专业内几个通用的理论或技术基础问题为背景，要求学生,通过直接阅读原版技术资料掌握相关的知识和技能,通过阅读本专业典型技术资料对相关领域内的常用,科技英语词汇、术语,有一个初步印象,本课程由二个部分组成：,4,教学参考书,激光和电光学(英文版)C.C.Davis主编 世界图书出版公司,电子科学与技术专业英语.光电子技术分册 张爱红主编 哈尔滨工业大学出版社,教学参考书 激光和电光学(英文版)C.C.Davis,5,激光,英语,Unit 1,fundamentals of lasers,Unit 2,Basic Constructions of Lasers,Unit 3,properties of laser beams,Unit 4,properties of laser beams,Unit 5,laser oscillation in optical resonator,Unit 6,Solid-State Lasers,Unit 7,Solid-State Lasers（continue）,激光英语Unit 1 fundamentals of la,6,激光,英语,Unit 8,gas dynamic lasers,Unit 9,q-switching,Unit 10,Laser Technology,Unit,11,Laser Machining Processes,Unit,12,Laser Welding,Unit 1,3,Laser Cutting,Unit 1,4,Laser drilling and marking,激光英语Unit 8 gas dynamic lasers,7,激光,英语,Unit,15,measurement with a laser,Unit,16,laser radar,Unit 1,7,optical communications,Unit,18,other applications of lasers,激光英语Unit 15 measurement with,8,Text 1 fundamentals of lasers,Optical Amplification,1、,To understand the operation of a laser we have to know some of the principles go,v,erning the interaction of,radiation,with,matter.,1光放大,要了解激光器如何运转，就必须弄清楚决定,辐射,与物质相互作用的有关原理,。,Text 1 fundamentals of lasers,9,2、,Atomic systems such as atoms,ions,and,molecules,can exist only in discrete,energy states.,A change from one energy state to another,called a,transition,is associated with,either the emission or the absorption of a,photon,.The wavelength of the,absorbed or emitted radiation is given by Bohrs,frequency,relation,原子系统，诸如原子、离子和分子，只存在于分立的能态，从一个能态到另一个能态的变化称为跃迁，它伴随着光子的发射或吸收.波尔频率关系式给出了吸收或发射辐射的波长,。,2、Atomic systems such as atom,10,3、,where E2 and E1 are two,discrete energy levels,V21 is the frequency,and h is the,Plancks constant,.An,electromagnetic wave,whose frequency,V,2,1,corresponds to,an energy gap of such an atomic system can interact with it.,E,2,一E,1,=,h,v21式中，E,2,E1是两个离散的能级，v21为频率，h是普朗克常量，与这一原子系统的能隙相对应的是频率为u,21,的电磁波，该电磁波与原子系统能够相互作用.,3、where E2 and E1 are two disc,11,4、,At,thermal equilibrium,the lower energy states in the,material are more heavily populated than the higher energy states.A wave interacting,with the substance will raise the atoms or molecules from lower to higher energy,levels and thereby experience absorption.,在热平衡时，材料中处于下能态的粒子数远比上能态的多，电磁波与其发生相互作用，使原子和分子从低能级上升到高能级，即为吸收.,4、At thermal equilibrium,the,12,5,、The operation of a laser requires that the energy equilibrium of a laser material be,changed such that energy is stored,in the atoms,ions,or,molecules of this material.This,is achieved by an external pump source which transfers electrons from a lower energy,level to a higher one.,激光器运转要求改变激光材料的能量平衡，使能量存储于该材料的原子、离,子,或分子之中.通过外部泵浦源使激光材料中的粒子从低能态跃迁到高能态.,5、The operation of a laser re,13,6、,The pump radiation thereby causes a,population inversion,”,An,electromagnetic wave,of appropriate frequency,incident on the inverted laser,material,will be amplified because the incidentphotons cause the atoms in the higher,level to drop to a lower level and thereby emit additional photons.As a result,energy,is extracted from the atomic system and supplied to the radiation field.The release of,the stored energy by interaction with an electromagnetic wave is based on stimulated,or,induced,emission.,泵浦辐射导致“粒子数反转”.使频率适中的电磁波入射到该“反转的”激光材料上，入射光子将促使高能级的原子降落到低能级而发射出附加的光子，形成光波放大。最终，能量从原子系统出来，供给到辐射场.原子系统与电磁波相互作用而释放出原先存储的能量，这是以受激发射或感应发射为基础的.,6、The pump radiation thereby,14,7、,Stated very briefly,when a material is excited in such a way as to provide more,atoms(or molecules)in a higher energy level than in some lower level,the material,will be capable of amplifying radiation at the frequency corresponding to the energy,level difference.The,acronym,laser derives its name from this process:Light,Amplification by Stimulated Emission of Radiation,.”,简言之，当材料受到激励，使得它的原子(分子)在高能级的分布多,于,低能级时，该材料就能够以与能级差相应的频率使辐射放大.英文中的“激光”正是“受激辐射光放大”之,略语,.,7、Stated very briefly,when a,15,8、Boltzmanns Statistics According to a,basic principle,of,statistical mechanics,when a large collection of similar atoms is in thermal equilibrium at temperature T,the relative populations of any two energy levels E1 and E2,such as the ones shown in Fig.1.1,must be related by the Boltzmann ratio,波尔兹曼统计,根据统计力学的基本原理，当大量近似的原子在温度T处于热平衡状态时任何两个能级E:和E:的相关粒子数(如图1.1所示)一定与波尔兹曼比值有关。,8、Boltzmanns Statistics Accor,16,9、,9、,17,10、,Population Inversion,According to the Boltzmann distribution(1.7),in a collection of atoms at thermal equilibrium there are always fewer atoms in a higher-lying level EZ than in a lower level Ei.Therefore the population difference N1一N2 is always positive.,根据波尔兹曼分布，对于一热平衡条件下的原子集合，高能级E2的原子数比低能级E1原子数少，因而粒子数差N1一N2总是正值。,