2. Optoelectronics, the rapid development mainly based on quantum mechanics and materials science in the development, with particular attention is the development of optoelectronic semiconductors. LED, LD Shenqi these electronic devices is the result of this development, particularly the recent development of the organic photoelectric materials, and more is great to promote the progress of the photoelectric materials.
Why is the first semiconductor LED »
When the electronic conduction band jumped from the top to enter the zone at the time, a certain loss of energy, the energy becomes a photon emission out, is popular to say that the luminescence. Oh:) semiconductor laser is a direct bandgap semiconductor materials constitute the PN junction of material or PIN entered into a small laser. Semiconductor laser work of dozens of substances, has made laser Jia arsenide semiconductor material (GaAs), arsenic Gu (InAs), gallium nitride (GaN), antimony and Gu (InSb), curing the pot (cds), hoof-fu (CdTe), lead selenide (PbSe), tellurium and lead (PhTe ), Al Jia arsenic (A1xGa, -, As), Gu phosphorus arsenic (In-PxAS), and so on. Semiconductor laser incentive There are three main ways, that is, people-Note, optical pump-and-high-energy electron beam incentives. The vast majority of Semiconductor laser is the way of incentives, Notes, or to Pn guitar and forward voltage, so that the guitar in a regional plane stimulated emission, that is a positive bias of the diodes, also known as the semiconductor laser diode laser diode . On the semiconductor, electronics is due in the transition between the band, rather than in discrete energy levels between the transition, the transition energy is not a set value, which makes semiconductor laser output wavelength distribution in a very broad The scope. They issued by the wavelength of between 0.3-34um. Wavelength range of its decision on the materials used by the band gap, the most common is AlGaA: double-heterojunction laser, the output wavelength of 750 - 890nm. The world On the first semiconductor laser is available in 1962, after several decades of research, semiconductor laser achieved a surprising development, and its infrared wavelengths from the red light green to blue, gradually expanding the scope covered, the performance Parameters also have greatly increased their production by the proliferation of technology has to LPE Law Act (LPE), extension of gas (VPE), MBE Act (MBE), MOCVD method (metal organic compounds vapor deposition) , Chemical beam epitaxy (CBE) and their various combined, and other technology. Lasing closure of its current value from a few hundred mA down to a few dozen mA, until the sub-mA, its life expectancy by a few hundred to tens of thousands of hours, and 1 million hours from the initial low-temperature (77 K) under development to operate at room temperature for work, the power output by several milliwatts to kilowatts level (Array) it has a high efficiency, small size, light weight, simple structure, can Power for the direct conversion of laser energy, high power conversion efficiency (has reached more than 10 per cent, up to 50 per cent). Facilitate direct modulation, power-saving advantages, applications growing. At present, the fixed-wavelength laser diode to use the number of Habitat All of the first laser, the application of certain important areas over the past used the other lasers, has gradually been replaced by a semiconductor laser.
Semiconductor Laser is the biggest drawback: laser properties affected by temperature, the beam divergence angle greater (in general several times to 20 degrees), so in the direction and coherence of monochrome and other poor areas. But with the With the rapid development of science and technology, the semiconductor laser-depth study positive direction, the performance of semiconductor laser continuously improve. Semiconductor laser power can reach very high level, and beam quality has been greatly improved. Semiconductor laser as to The core semiconductor photonics technology in the 21st century information society will make more progress, play a bigger role.
听我娓娓道来。首先，激光的英文叫Laser light amplification by stimulated emission of radiation. 就是通过受激发射实现光放大。
光通过谐振腔的选模作用和增益介质的放大作用，经过震荡和放大，实现拥有单色性、准直性、相干性非常好的光束，这个就是激光。
激光器有很多种类型，但他的必要组成部分无外乎： 谐振腔、增益介质、泵浦源。
形成激光的一个重要条件是，粒子数反转，就是导带的粒子数密度大于价带（半导体）或高能级的粒子数密度大于低能级（气体或固体），激光的现象就是在这样一种偏离了平衡态的稳态。
半导体激光器比起固体激光器和气体激光器，结构上还是有很大区别的。半导体激光器一般是三层或多层异质结结构，这样由于折射率的的内大外小自然构成了光约束，又由于异质结结构形成的量子井结构（最早的半导体激光器不是量子井结构的，随着MBE的半导体加工技术的应用，单井和多井结构得以实现），对载流子形成了约束，使受激发射大都发生在增益介质的带边，这样就大大提高了激光器的效率。 半导体激光器是电泵浦的，不同于气体激光器或固体激光器的光泵浦。
半导体激光器的工作过程是这样的，由于外加电场的作用，载流子开始移动，由于量子井的存在，载流子开始在量子井中堆积，然后一部分导带的电子会自发跃迁回价带放出一个能量等于带隙宽度（band gap）的光子，这个过程叫自发发射，一部分自发发射的光子会被吸收，再放出两个光子，这个过程叫受激发射，这样自发发射的光子成为了最初的泵浦光，然后不断的发生受激发射，受激发射的光子会在增益介质中不断震荡，不断的使更多的光子受激发射出来，当外加电场强度达到粒子数反转所需强度之后一段时间，便会有稳定的激光输出了。
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这个过程当中有很多很多细节问题，不明白可以问我。
Also known as laser diode laser diode (LD). Into the 1980s, it absorbed the physical development of the semiconductor up-to-date results, the use of quantum well (QW) and strained quantum well (SL-QW) structures, such as novelty, the introduction of the refractive index modulation Bragg launchers, as well as to enhance Bragg modulation transmitter The latest technology, as well as the development of the MBE, MOCVD and the CBE, such as crystal growth technology of the new technology, making new epitaxial growth technology to precisely control crystal growth to the accuracy of atomic layer thick, high-quality growth of quantum wells, as well as strained quantum well materials. As a result, production of the LD, the current threshold of a significant decline in conversion efficiency has been greatly improved the power output doubled, significantly longer service life.A low-power LD
In the field of information technology for the rapid development of low-power LD. For example, for fiber-optic communications and optical switching systems distributed feedback (DFB) and the dynamic single-mode LD, narrow linewidth tunable DFB-LD, such as CD-ROM for information processing technology in the field of visible light Wavelength (such as wavelength of 670nm, 650nm, 630nm The blue-green to red) LD, surface-emitting quantum well, as well as ultra-short laser pulses substantive, which are all treated the development of LD. The development of these devices are: narrow-linewidth single-frequency, high-speed, as well as short-wavelength tunable optical and integrated single-chip, and so on.
B high-power LD
In 1983, a single wavelength of 800nm output power LD more than 100mW, to 1989, 0.1mm-wide LD be reached 3.7W continuous output, and 1cm linear array LD has reached 76W output, the conversion efficiency of 39%. In 1992, the Americans also targets to a new level: 1cm linear array LD CW output power up to 121W, the conversion efficiency of 45%. Now, the output power of 120W, 1500W, 3kW and many other high-power LD have been published. High-efficiency, high power LD array and its rapid development for all-solid-state laser, diode laser that is pumped (LDP) of the rapid development of solid-state laser provides strong.
In recent years, in order to adapt to the EDFA and the EDFL, and other needs of the wavelength of 980nm high-power LD is that there is great development. Fiber Bragg Grating with recently selected frequency for filtering, a significant improvement in the stability of its output, pump effectively improve the efficiency.
And the characteristics of the application: semiconductor diode laser is the most important practical for a class of lasers. Its small size, long life, and a simple injection of current-pumped his way to work with the voltage and current circuit-compatible, which can be integrated with a single. And also can be as high as GHz frequency modulation direct current for high-speed modulation of laser output. As a result of these advantages, the semiconductor diode laser in the laser communications, optical storage, optical gyros, laser printing, as well as radar range, and so on, as well as access to a wide range of applications.
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