Laser technology has become one of the irreplaceable technologies in modern life. Whether it is industrial processing, medical beauty, optical fiber communication, or the fiery unmanned driving and intelligent robots in recent years, it is closely related to laser technology.
Unlike traditional high-power lasers, the development of semiconductor lasers is difficult, and the laser industry has a long way to go. The subject of our article today is semiconductor lasers, HTPOW will bring everyone to review its development history and applications.
From theoretical development to laboratory development
The origin of the laser can be traced back to the "Quantum Theory of Radiation" published by Einstein in 1916. Einstein first proposed the theory of stimulated radiation, which provided a theoretical basis for the development of lasers in the future. Forty years later, the topic of whether lasers can be formed from semiconductor materials began to be noticed by physicists. Forty years later, the topic of whether lasers can be formed from semiconductor materials began to be noticed by physicists.
After several years of demonstration and experimentation, homo junction GaAs semiconductor lasers were introduced in 1962. However, since the critical current density of the homo junction semiconductor laser is high, continuous excited excitation cannot be achieved at room temperature, resulting in almost no practicality. Therefore, the research direction of semiconductor lasers points to "continuous stimulated excitation at room temperature".
In order to solve the problem of high critical current density, scientists have proposed the concept of a hetero structure semiconductor laser, which effectively reduces the critical current density by forming a "junction" with a thin layer of semiconductor material with different band gaps. In 1967, single hetero junction semiconductor lasers were introduced. Compared with the homo junction semiconductor laser, the critical current density of the single hetero junction semiconductor laser has been greatly reduced, but it is still at a higher position, failing to achieve the research goal of continuous stimulated excitation at room temperature. Nevertheless, the historical status of single hetero junction semiconductor lasers can not be underestimated. The hetero junction structure and liquid phase epitaxy technology used provide important theoretical basis and technical support for the following research.Stable excitation, improved life, semiconductor lasers to practical applications
The successful use of hetero structures has pointed the way for scientists
Since the critical current density of a single hetero junction semiconductor laser is still high, what is the effect of the double hetero structure?
In September 1969, the Leningrad Ioffe Institute released preliminary research results on double hetero semiconductor lasers (AlxGa1-xAs--GaAs). At the beginning of 1970, Bell Labs successfully reduced the critical current density of double hetero semiconductor lasers, achieving continuous excitation at room temperature, and declaring the introduction of double hetero semiconductor lasers. In May of the same year, the Leningrad Ioffe Institute also successfully achieved continuous stimulated emission of double hetero semiconductor lasers at room temperature.
Continuous stimulated emission at room temperature is the first step toward the practicality of the laser. Solving the problem of being usable at room temperature, it is necessary to consider the problem of durability at room temperature, and the research direction of semiconductor lasers has also turned to "to achieve long life and stability of the device".
International researchers have gradually improved the working life of semiconductor lasers by continuously improving the device structure. In 1977, double-heterogeneous short-wavelength semiconductor lasers were continuously operated for 1×106 hours. Since then, the United States, Japan and other countries have studied the improvement of device structure, improving device stability, reducing losses, etc., and developed AlGaAs-GaAs lasers with CDH, BH, TJS, CDH and other structures, all of which have achieved continuous excitation under the greenhouse. And single-model work.
The emergence of long-life light sources has paved the way for semiconductor lasers to go to practical applications. The researchers found that the wavelength of the semiconductor laser is very compatible with the fiber, which is very suitable for fiber-optic communication. Therefore, the semiconductor laser has been built on the development of optical fiber communication, and it is also advancing the development of the optical communication industry.