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, NdYVO, 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-modelpressure narrow spectral line width to improve beam The time coherencefurther 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 wattstemperatures as high as several characteristics of Baidulaser threshold current of less than 1 mAmultiple 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.
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