What Is A Semiconductor Lasers?（Part Ⅱ）

Semiconductor Lasers belongs to a kind of solid-state laser, is a semiconductor material as the laser medium, to current injection diode source region as the pumping mode of laser diode (electron excited radiation to produce light). Among all kinds of lasers, the semiconductor laser has the best energy conversion efficiency (the electro-optical conversion efficiency of high-power semiconductor laser components directly applied can reach up to 60-70%). It can be used as the core pump source of fiber laser, solid laser, and other kinds of optical pumping laser, and promote the rapid development of fiber laser and solid laser technology. (Continue with Part Ⅰ)

3. Development history of semiconductor laser

The semiconductor laser in the early 1960s is a homogeneous junction laser, which is a pn junction diode made on a kind of material. Under the forward current injection, electrons are continuously injected into the P-zone and holes are continuously injected into the N-zone. As a result, the reversal of carrier distribution is realized in the original pn junction depletion region. Since the electron migration speed is faster than the hole migration speed, radiation and recombination occur in the active region, emitting fluorescence, and laser occurs under certain conditions. This is a kind of semiconductor laser that can only work in the form of a pulse. The second stage in the development of the semiconductor laser is the heterostructure semiconductor laser, which consists of two thin layers of semiconductor materials with different bandgaps, such as GaAs and GaAlAs. The single heterostructure laser appeared first (1969). In order to reduce the threshold current density of GaAsP-N junction, the value of SHLD is one order of magnitude lower than that of homogeneous junction laser, but the SHLD still cannot operate continuously at room temperature.

Since the late 1970s, the semiconductor laser has been developing in two directions, one is the information laser for the purpose of transmitting information, and the other is the power laser for the purpose of improving optical power. Driven by the application of pumped solid state laser, high power semiconductor laser (continuous output power above 100mw, pulse output power above 5W, can be called high power semiconductor laser).

Breakthrough progress has been made in the 1990s, marked by a significant increase in the output power of semiconductor lasers. High-power semiconductor lasers of kilowatt levels have been commercialized abroad, and the output of domestic sample devices has reached 600W. If from the point of view of the expansion of the laser band, the first infrared semiconductor laser, followed by a large number of 670nm red semiconductor laser into the application, and then, wavelength 650nm, 635nm came out, blue light, the blue light semiconductor laser has been successfully developed, 10mW violet and even ultraviolet semiconductor laser, It is also under development. In the late 1990s, surface-emitting lasers and vertical-cavity surface-emitting lasers have been developed rapidly, and many applications in ultra-parallel optoelectronics have been considered. 980nm, 850nm, and 780nm devices have been used in optical systems. At present, vertical-cavity surface-emitting lasers have been used in gigabit Ethernet high-speed networks.

4. The application of semiconductor laser

The semiconductor laser is mature earlier, with faster progress of a class of lasers, because of its wide wavelength range, simple production, low cost, easy mass production, and because of small size, lightweight, long life, therefore, varieties of rapid development, a wide range of application, has more than 300 kinds.

1) Application in industry and technology

① Optical fiber communication. The semiconductor laser is the practical light source of an optical fiber communication system. Optical fiber communication has become the mainstream of contemporary communication technology.

②Optical disc access. Semiconductor lasers are already used in optical disk memory, which has the advantage of storing a large amount of information about sound, text, and pictures. Using blue and green lasers can greatly improve the storage density of CDs.

③Spectral analysis. Far infrared tunable semiconductor laser has been used in environmental gas analysis, monitoring air pollution, automobile exhaust, and so on. It can be used in industry to monitor the process of gas deposition.

④Optical information processing. Semiconductor lasers have been used in optical information systems. Surface emission semiconductor laser two-dimensional array is an ideal light source for optical parallel processing systems, which will be used in computers and optical neural networks.

⑤Laser microfabrication. With the help of the high-energy ultra-shire laser produced by the Q switch semiconductor laser, the integrated circuit can be cut, punched, etc.

⑥ Laser alarm. Semiconductor laser alarm is widely used, including burglar alarm, water level alarm, car distance alarm, etc.

⑦Laser printer. High power semiconductor lasers are already used in laser printers. Using blue and green lasers can greatly improve printing speed and resolution.

⑧ Laser bar code scanner. Semiconductor laser barcode scanners have been widely used in the sale of goods, as well as books and archives management.

⑨Pump the solid-state laser. This is an important application of high-power semiconductor lasers, which can be used to replace the original atmosphere lamp and form an all-solid-state laser system.

⑩ High-definition laser television. In the near future, semiconductor laser television sets without cathode-ray tubes could be put on the market, using red, blue, and green lasers that are estimated to consume 20 percent less power than existing sets.

2) Applications in medical and life science research

① Laser surgery. Semiconductor lasers have been used for soft tissue excision, tissue bonding, coagulation, and vaporization. General surgery, plastic surgery, dermatology, urology, obstetrics, gynecology, etc., are widely used in this technology.

②Laser dynamic therapy. The photosensitive substances that have an affinity to the tumor are selectively gathered in the cancer tissue, and the cancer tissue is irradiated by the semiconductor laser to produce reactive oxygen species, aiming to make it necrotic without damaging the healthy tissue.

③ Life science research. "Optical tweezers", which use semiconductor lasers to snatch live cells or chromosomes and move them wherever they want, have been used to improve cell synthesis, cell interactions, and forensic diagnostics

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