1958, American scientists Schawlow and Townes put forward the "laser principle", that is, when a substance is excited by energy with the same natural oscillation frequency as its molecule, it will produce this kind of non-divergent strong light-laser. He published a paper for this and won the 1964 Nobel Prize in Physics.

1960 On July 7th, Theodore Mayman announced the birth of the world's first laser. Maiman's plan is to use high-intensity flash tubes to excite rubies.

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The color of laser depends on the wavelength of laser, and the wavelength depends on the active substance that emits laser, that is, the substance that can generate laser after being stimulated. Stimulating ruby can produce a deep rose laser beam, which is used in medical fields, such as treating skin diseases and surgery.

Argon is one of the most precious gases, which can produce blue-green laser beams. It has many uses, such as laser printing, and it is also indispensable in microsurgery. The laser produced by semiconductor can emit infrared light, so our eyes can't see it, but its energy can just "interpret" the optical disk and can be used for optical fiber communication. But some lasers can adjust the wavelength of the output laser.

Laser has many characteristics: first, laser is monochromatic, or single frequency. Some lasers can produce lasers with different frequencies at the same time, but these lasers are isolated from each other and used separately.

Secondly, the laser is coherent light. The characteristic of coherent light is that all its light waves are synchronous, and the whole beam of light is like a "wave train". Thirdly, laser is highly concentrated, that is, it needs a long distance to disperse or converge.

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