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Homojunction and heterojunction lasers. History of the development of semiconductor lasers. Early 1960s, the semiconductor laser is a homojunction laser, it is a material produced by the pn junction diode. Positive current injection, electronic to the P region into the hole to a "one district into a result, the reversal of the carrier distribution in the pn junction depleted region, due to electronic migration speed is faster than the migration speed of the hole radiation in the active region, composite, and the emitted fluorescent. Light, under certain conditions the laser. This is the work of one kind only in pulses semiconductor lasers. Especially when the customer goes for sporting or camping outdoors,  china laser pointer are good tools for the customer.
The second phase of development of the semiconductor laser heterostructure semiconductor lasers, which is composed of two different band gap semiconductor thin layers of material. Such as of GaAs. The GaAIAs the composition, the first there is a single-heterostructure lasers (1969). Single-heterostructure injection lasers (SHLD) is the use of heterojunction barrier limiting the injected electrons within the GaAsP-P-N junction area, thereby reducing the threshold current density, and its values than homojunction lasers reduce an order of magnitude, the single-heterojunction lasers still can not work continuously at room temperature. In 1970, a laser wavelength of 9000A, the room temperature continuous dual the heterojunction caAs-GaAlAs (gallium arsenide, gallium aluminum arsenide) laser. There is still a kind of multiple function charger of china laser pointer.
The birth of the double heterostructure laser (DHL), continue to broaden the available band, gradually increase the line width and tuning performance, its structure is characterized by growth in the P-type and n-type material between only 0. 2tt. m thick and doped with a thin layer of narrow bandgap materials, so the Note A. 00 carrier is limited in the region (active region), and therefore less current injection can be achieved reversal of the carrier number. In the semiconductor laser device. More mature, better performance, wider application of electrically injected GaAs diode laser with double heterostructure. As heterojunction laser research and development, coupled as MBE, MOCVD technology achievements. The customer who uses it is very satisfied with this kind of china laser pointer.
Thus, in 1978 the world's first semiconductor quantum well lasers (QWL), it substantially improved the variety of properties of semiconductor lasers. Later, due by MOCVD, MBE growth techniques mature, to grow high-quality ultra-fine thin layer of material, after they successfully developed a more favorable performance of quantum well lasers, quantum well semiconductor lasers with double heterostructure (DH ) lasers, compared with a low threshold current, high output power, frequency response, narrow spectral line and temperature stability and high optical conversion efficiency of a number of advantages. From the late 1970s, semiconductor lasers significantly towards the development of two directions, one is based on laser transmission of information for the purpose of information. The customer can buy the disposable type or rechargeable type battery of china laser pointer according to the actual need.
The other is to improve power laser optical power for the purpose. Pumped solid state lasers and other applications driven by high power semiconductor lasers (continuous output power in 100mw above, the pulse output power of 5W more than can be known that the high power semiconductor lasers) in the 1990s achieved a breakthrough in , marked by a significant increase in the output power of semiconductor lasers, foreign-kilowatt high-power semiconductor lasers have been commercialized, domestic sample device output has reached 600W. The band extended from the laser point of view, the first infrared semiconductor laser, followed by a large number of red semiconductor laser 670hm into applications. It is the multiple function charger of green laser pointer.