What Kinds Of Lasers Are There? (Part 1)

Lasers is known as "the most accurate ruler", "the fastest knife", and "the brightest light", and is one of the four major inventions of 20th-century computer technology, atomic energy technology, and semiconductor technology. At present, the laser is widely used in all walks of life because of its very advantageous characteristics, including sheet metal cutting, industrial manufacturing, food medical, aerospace, and so on. With the vigorous development of the high-tech manufacturing industry represented by new energy vehicles, laser technology has gained a broader space for play.

As the core component of all laser applications, the laser is the most important part of all laser applications. And there are many types of lasers. Below, it will be classified from several aspects such as laser working material, excitation mode, operation mode, output wavelength range, etc.

1. Classified by work material

According to the different states of the working material, all lasers can be divided into the following categories:

①solid (crystal and glass) lasers, the working substance used by such lasers is made by incorporating metal ions that can produce stimulated radiation into a crystal or glass matrix to form a luminous center;

② Gas lasers, the working substance they use is gas, and according to the difference in the nature of the working particles that really produce stimulated emission in the gas, it is further divided into atomic gas lasers, ionic gas lasers, molecular gas lasers, excimer gas lasers, etc.;

③ Liquid lasers, the working substances used by this type of laser mainly include two categories, one is an organic fluorescent dye solution, the other is an inorganic compound solution containing rare earth metal ions, in which metal ions (such as Nd) play the role of working particles, and inorganic compound liquids (such as SeOCl) play the role of the matrix;

④ Semiconductor lasers, this kind of laser is a certain semiconductor material as a working substance to produce stimulated emission, the principle is through a certain excitation method (electric injection, optical pump, or high-energy electron beam injection), between the energy bands of semiconductor materials or between the energy bands and impurity levels, by stimulating non-equilibrium carriers to achieve the number of particles inversion, The stimulated emission of light is produced.

⑤Free electron laser, this is a special type of new laser, the working substance for the high-speed movement of the directional free electron beam in the spatial periodic change of the magnetic field, as long as the speed of the free electron beam can be changed to produce tunable coherent electromagnetic radiation, in principle, the coherent radiation spectrum can be transitioned from the X-ray band to the microwave region, so it has a very attractive prospect.

2. Classified by motivation

① Optical pump laser. It refers to lasers excited by optical pumping, including almost all solid lasers and liquid lasers, as well as a few gas lasers and semiconductor lasers.

② Electrically excited laser. Most gas lasers are excited by gas discharge (DC discharge, AC discharge, pulse discharge, electron beam injection), while most common semiconductor lasers are excited by junction current injection, and some semiconductor lasers can also be excited by high-energy electron beam injection.

③ Chemical laser. This is a laser that uses the energy released by the chemical reaction to stimulate the working substance, and the chemical reaction produced can be triggered by light, electric discharge, and chemical initiation respectively.

④ Nuclear pumped laser. It refers to a class of special lasers that use the energy released by small nuclear fission reactions to excite working substances, such as nuclear-pumped helium-argon lasers.

3. Classified by mode of operation

Due to the different working substances, excitation methods, and application purposes used by the laser, it's operation mode and working state are also correspondingly different, which can be divided into the following main types.

① Continuous lasers, whose work is characterized by the excitation of the working substance and the corresponding laser output, can be continued in a continuous manner within a long time range, solid lasers excited by continuous light sources and gas lasers and semiconductor lasers working in a continuous electrical excitation mode are of this class. Due to the inevitable overheating effect of the device during continuous operation, most of them need to take appropriate cooling measures.

② Single-pulse lasers, for such lasers, the excitation of the working substance and the corresponding laser emission are a single-pulse process from the time point of view, general solid lasers, liquid lasers, and some special gas lasers, all operate in this way, at this time the thermal effect of the device can be ignored, so special cooling measures can not be taken.

③ Repeated pulse laser, this type of device is characterized by its output for a series of repeated laser pulses, for this reason, the device can be stimulated by repeated pulses, or in a continuous way to stimulate but in a certain way modulated laser oscillation process, in order to obtain repeated pulse laser output, usually also requires the device to take effective cooling measures.

④ Tunable laser, which specifically refers to the use of a certain switching technology to obtain a higher output power of the pulse laser, its working principle is in the working substance after the formation of the particle number reversal state does not make it produce laser oscillation (the switch is in the off state), the number of particles accumulated to a high enough degree, suddenly turn on the switch. Thus, very strong laser oscillation and high-power pulse laser output can be formed in a short time (such as 10 to 10 seconds)

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