The origin and development of laser devices

In 1960, Maimen invented the ruby ​​laser. The main difference between laser and ordinary light is that the optical frequency of laser is very simple and has linear spectrum. It is called coherent light in optics and is most suitable for optical fiber communication light source. The light frequency of ordinary light is very messy, it contains many wavelengths. The light frequency of ordinary light is very messy, it contains many wavelengths. The characteristic of coherent light is that the light energy is concentrated, the divergence angle is very small, and it is similar to parallel light. After the invention of the ruby ​​laser, various lasers were born: gas lasers, such as helium-neon lasers; solid-state lasers, such as YAG iridium aluminum garnet lasers; chemical lasers; dye lasers, etc. Among them, the semiconductor laser is the most suitable light source for optical fiber communication. It is small in size, high in efficiency, and its wavelength is compatible with the low loss window of optical fiber. However, the manufacturing process of semiconductor lasers is very complicated. It is necessary to epitaxially grow 5 layers of doped semiconductors on extremely high-purity and defect-free substrate materials, and then lithographically engrave micron-sized optical waveguides on it. Compared with optical fibers, it is more difficult. Nothing less. At the end of the 1970s, a long-life semiconductor laser with continuous working at room temperature was finally made. In 1976, the world’s first practical optical fiber communication line was established from Atlanta to Washington. At this time, the semiconductor laser has not passed the test, and the light source is a semiconductor light-emitting tube. In the early 1980s, single-mode fibers and lasers had matured, and since then the superiority of large-capacity optical fiber communications has gradually been brought into play.
The light emitted by the semiconductor laser has a pure spectrum, concentrated energy, and a very thin beam, which can efficiently shoot into a single-mode fiber with a core diameter of only 8 microns. Today’s high-speed optical fiber communication system uses semiconductor lasers as light sources.