光电子学chapter.ppt

Laser Diode Chapter 7 Some Specific Laser Systems 雷射种类 雷射种类 continued 雷射应用 (3) 、high correlation (相关性) Laser’s frequency , phase , direction of librations (振动) are all coherent(一致的), so its correlation is very high. (4)、strong direction Common light is emitted towards far and near (四面八方) , but the laser beam transmit directed(定向的).and laser radiation’s(发散) angle is very small , it close to parallel light . because laser radiation’s angle is very small , it can transmit far from lamp-house (光源) . Owing to the advantages of laser , on the high road of information in future , it can be applied far and wide (广泛的) ： for example , fiber is primary channel to translate data in the high road of information . At the same time , laser beam can be made much thin than fiber , so the fiber can use laser beam translate information in it . 7.1 the theory of excitated radiation Lasing Principle The characteristics about spontaneous (自发的)radiation: un-ruled , spontaneous, stochastic (随机的) , in a word it is an un-correlative (相关的) radiation and a noise. The characteristics about excitated(激发)radiation: there are four uniform aspects, the same polarized direction (偏振方向), the same frequency, the same phase and the same radiated direction. Off from work 请假了 My personnel-management class consisted mainly of adult, working students. One night while discussing job enrichment, the teacher asked if any of us would be happy doing what we did that day for the rest of our lives. A student in the back raised his hand. Surprised, the teacher asked him, What did you do today? Smiling, he said, I took off from work. 我曾参加过一个员工管理培训课程，我们班上基本上都是成年人和一些半工半读的学生。一天晚上我们在课上讨论工作丰富化的问题。我们的老师问我们当中有没有人愿意一辈子做今天所做的事情。坐在教室最后面的一个学生举起了手。老师觉得很惊奇，于是问那个学生，“你今天做什么来着？”，学生笑着回答，“我今天请假了”。 7.2 the technology of pumping 7.3 pumping and laser efficiency It is evident from this figure that the minimum energy input per output photon is hv3