以半导体激光器为例说明产生激光的原理和条件

首先你说的1.52μm是发射波长,不是频率.不同波长的激光器可以用在不同的系统中,主要是指光纤通信系统.GaInNAs/GaAs激光器做到1.52μm波长的意义是,在这个波长的半导体激光器一般都采用InP衬底,而采用GaAs衬底则可以降低器件的成本,而且可以利用GaAs系材料优势实现大规模的光电子集成.

从激光
哪里
看
度数

从原理上讲,是属于半导体激光器的.

This artical brifly introduce the significant tache of making semiconductor laser device.

.钢尺测量波长?因为实际误差比较大,所以测量的可能性近乎为0.

呵呵,都给了这么详细的数据了还不好算?
0.5mW即 -3dBm.
光纤衰减 25dB, 连接器应该用26个,衰减 13dB;
再加6dB系统裕量, 要求总衰减 44dB.
-40dBm的灵敏度显然不够了,只能选 -59dBm的APD了,其实有 -47dBm就够了.

Fourth,the rapid development of laser diode
Since 1970,the semiconductor laser has been rapid development.Speed of its development,the application scope of the development potential is large by any other laser can not be compared.So its case,there are two important reasons.
1.Semiconductor lasers have the advantage of many prominent
(1) semiconductor laser is declared to a photon of electronic converters and thus its high conversion efficiency.Theoretically,the laser diode within the accessible 100% quantum efficiency,in fact because of the existence of certain non-radiation losses,the quantum efficiency is much lower,but still can reach more than 70 percent.
(2) laser diode-band covered by the widest range.Can choose different semiconductor laser multi-active material or change the element compound semiconductor components,and received a wide range of lasing wavelength to meet different needs.
(3) the longest life of the semiconductor laser.Currently used for optical fiber communication semiconductor laser,its working life up to hundreds of thousands or even 1 million hours.
(4) the ability to have a direct modulation is different from other laser diode laser an important characteristic.
(5) laser diode small size,light weight,cheap,which is second to none other lasers.
2.And the practical application of the laser diode to promote mutual development
As early as l967,the single heterojunction lasers there before.At that time,the British Chinese scholars Dr.Gao Kun in 1965 first proposed the use of optical fibre to transmit information theory and the initial experiment.But then the loss optical fiber for 1000 dB / km,at the very end of the same semiconductor laser can only work in the temperature of liquid chlorine in the same situation,so much loss of fiber is also no practical value,but it was noted that by using optical fiber With sleeves instead of the obvious advantages of cable-Seoul laboratory is aware of semiconductor lasers in optical fiber communications to the important role and begin a semiconductor laser and optical fiber technology in the development of parallel.At room temperature semiconductor lasers to achieve continuous work in 1970,the optical loss also significantly dropped to 2 dB / km.Subsequently,the development of a wide range of semiconductor laser bar,or its current threshold necessary for the current continue to lower,thus the work of the Stability and constantly improve the life of the device.At the same time,the loss optical fiber has been dropped,resulting in the USA and Asia in 1978 with Atlanta one of the world's first commercial optical fiber communication lines.This pace of development is unprecedented in the history of communications.

The first semiconductor lasers into practical,the lasing wavelength 0.83鍒?.85 um.This corresponds to the fiber loss spectrum of a window,multi-mode optical fiber loss of 2 dB / km.Centered on improving the capacity of optical fiber communication systems,in the 1970s-period.1.3 um wavelength in the loss was smaller (0.4 dB/km3,close to zero coefficient of dispersion single mode optical fiber.Soon after to develop further reduce the wear and tear 1.55um single-mode optical fiber
Window.Back in the late 1960s began to study the long-wavelength (1.3 ym) InGaAsP / InP laser also with single-mode optical fiber into the development of practical systems.1.55 uPm lasing wavelength of the laser diode was quick to practical use.To further to achieve the low threshold lasers,good dynamic single-frequency,high temperature and the characteristics of the work of the long-term stability,and have a lot of different structures,high-performance semiconductor lasers,such as the hidden bar buried heterojunction (BH ) Laser,distributed feedback (DFH) laser,sub-Bubu Bragg reflector (DBR) laser,cleavage coupled lasers and quantum well lasers,and so on.
Visible development of the momentum from semiconductor laser discs,optical-times the income copying and processing technology development.As early as 1974 the Netherlands,Philips Research experimental laser-start digital audio recording (DAD) Study.Okazaki in the record store data on the number of inverse laser beam focus will be on the spot diameter and the diameter is proportional to the wavelength of the laser.Therefore,in order to improve access to the information DAD density,to use the laser wavelength as short as possible sources.The first is the use of the He-Ne laser,but because of their size greenhouses limited life,the 1982 listing of the CD (CompactDisk) jukebox on a wavelength of 780 nm semiconductor laser.In recent years.A shorter wavelength such as the 30 nm semiconductor lasers have become commodities.Small size,low price and long life in the semiconductor laser optical information storage and processing has been the largest market.shan of laser research to promote a high-power laser diode (including the array of lasers) development.For there were iron-doped solid medium,such as Nd:YAG,Nd; YVO,such as the wavelength of 808 nm-effective around the peaks,with small size,lasing wavelength of 808 nm semiconductor laser instead of the usual-pumped solid-state laser materials,Can be small in size,Su Pu high efficiency (up to 70%) for dim light of the solid.
With REE-doped fiber amplifier,used as the source of pumping high-power laser diode was also another important application.For example,using wavelength of 980 nm or 1480 nm,for the tens of milliwatts of power semiconductor laser pump fiber,can get high-gain coefficient,so that optical signals are more than 30 dB gain.Fiber amplifier in the optical fiber communication has been critical applications.
In short,the need for a variety of applications,semiconductor laser beam is to improve the quality of development,reducing the beam divergence angle to enhance the coherence of space,increasing the high-speed modulation of the so-called dynamic single-model; pressure narrow spectral line width to improve beam The time coherence; further enhance the stability of temperature (that is,high temperature on the strength of the levy),the application of the laser diode is continuously expanding.
5,the band works so that semiconductor lasers generate a new leap forward with the molecular beam epitaxy (MBE) and metal organic compounds chemical vapor deposition (MOCVD) technology development and improvement,can grow to atomic size of the order of ultra-thin layer,which can Formation of the carrier into a holding it is the nature of quantum wells and superlattices.This is a band semiconductor and massive (often referred to as material) Semiconductor completely different shape and structure,and can,if necessary,by changing variables should be ultra-thin layer of the band structure change.The so-called "band project" or "band cutting project" to semiconductor laser with a new vitality,its device performance a big leap.For example,the quantum well semiconductor laser output power for up to tens of watts; temperatures as high as several characteristics of Baidu; laser threshold current of less than 1 mA; multiple quantum modulation doped laser relaxation oscillation frequency of up to 30 GHz,as usual Double-heterojunction semiconductor laser five times in the high-speed modulation than the width of the semiconductor laser is usually a low number
Order of magnitude,and so on.As quantum well (especially strained quantum well) structure emerges,the visible light laser diode increase the life span,the lasing wavelength further shortened.Have proven that the band works to fundamentally change the face of the semiconductor laser.In the near future,its continuous power output may reach several hundred watts and watts in order to enable it is not only a technical school in the field of information,but also in material processing,and to play an important role.

It introduced a nanosecond pulse driving circuit on lidar,laser communication aspects,etc,which makes use the avalanche effect of transistor to get nanosecond pulse,it analyzes the working principle of avalanche transistor and its application on nanosecond pulse driving circuit.
这里的雪崩效应:avalanche efect 应为avalanche effect

让光通过检偏器,旋转一周,出射光有两名两暗现象,在检偏器前插入四分之一波片,并使广轴方位于检偏器检得的暗方位垂直,再旋转检偏器一周,出现两明和两消光现象,说明是椭圆偏振光.

光缆损耗为4*10*0.5=20dB,连接器损耗为11*2=22dB,合计链路损耗为20+22=42dB,加上系统富余度6dB,共计最大链路损耗应为48dB.
入纤功率为0dB,减除链路损耗48dB,接收灵敏度应至少为-48dB.
答案明确：-56dBm灵敏度的APD接收机.和速率无关.

加个偏振片看看偏振方向会不会变化就知道了

采用倍频晶体的分离晶体式的半导体激光器,温度变化会影响波长,因为温度变化会造成热胀冷缩,改变倍频晶体的微观结构,从而改变波长,如果是半导体激光二极管直接发光的,波长变化受温度影响较小,但无论是那种半导体激光器,发光功率受温度的影响都是较大的……

解题思路：求出每个光子的能量，每秒内发出的光子数与每个光子能量的乘积是激光器每秒做的功，每个光子的能量E=hγ．

每个光子的能量E=hγ，
设每秒（t=1s）激光器发出的光子数是n，
则Pt=nE，即：P=nhγ，
n=[P/hγ]=
5×10−3
6.63×10−34×1014=7.54×10¹⁶；
故答案为：7.54×10¹⁶．

点评：
本题考点： 光子．

考点点评： 本题是一道难度不大，但综合性、代表性很强的题目，要注意掌握．

不能,功率放大对应的是光强增加,即光子个数增多,不会改变波长.波长取决于能级跃迁能量差,是定值.

对应的应该是LD允许的最大电流,超过这个电流会导致激光器损坏了,激光器的连续的还是脉冲的呢?

蓝光最大2w而且上千,所以啥3w,5w,10w的都是假的；绿光因为转换原因,1w最大,而且要两三千,所以几十几百的都不正版；红光因为最简单,技术也最成熟,所以红光也是最便宜的,几百就可以买到1w的.可以追加,