Lasers can be classified by pumping method, gain medium, operating method, output power, and output wavelength. 1) According to the pumping method: it can be divided into electrical pumping, optical pumping, chemical pumping, heat pumping, and nuclear pumping lasers. Electrically pumped lasers refer to lasers that are excited by current (gas lasers are mostly excited by gas discharge, while semiconductor lasers are mostly excited by current injection); optically pumped lasers refer to lasers that are excited by optical pumping (almost all solid-state lasers are excited by gas discharge). Lasers and liquid lasers are all optically pumped lasers, and semiconductor lasers are the core pumping source of optically pumped lasers); chemically pumped lasers refer to lasers that use the energy released by chemical reactions to excite working substances. 2) According to the operation mode: it can be divided into continuous laser and pulsed laser. The number of particles at each energy level in the CW laser and the radiation field in the cavity have a stable distribution. Its working characteristic is that the excitation of the working material and the corresponding laser output can be continuously and stably carried out in a continuous manner within a long time range, but the thermal effect. Obvious; pulsed laser refers to the time that the laser power is maintained at a certain value, and outputs the laser in a discontinuous manner. The main features are high peak power, small thermal effect, and good controllability. According to the pulse time length, it can be further divided into milliseconds, microseconds, nanoseconds, picoseconds and femtoseconds. The shorter the pulse time, the higher the single pulse energy, the narrower the pulse width, and the higher the machining accuracy. 3) According to output power: divided into low power (0-100W), medium power (100-1,000W), high power (above 1,000W), different power lasers are suitable for different application scenarios. 4) According to wavelength: it can be divided into infrared laser, visible light laser, ultraviolet laser, deep ultraviolet laser, etc. Substances with different structures can absorb different wavelengths of light, so lasers with different wavelengths are required for fine processing of different materials or different application scenarios. Infrared lasers and ultraviolet lasers are the two most widely used lasers: infrared lasers are mainly used in "thermal processing", heating and vaporizing (evaporating) substances on the surface of materials to remove materials; In the fields of wafer cutting, plexiglass cutting/drilling/marking, etc., high-energy ultraviolet photons directly destroy the molecular bonds on the surface of non-metallic materials, so that the molecules are separated from the object. For "cold processing", UV lasers have irreplaceable advantages in the field of micromachining. Due to the high energy of ultraviolet photons, it is difficult to generate a certain high-power continuous ultraviolet laser through an external excitation source. Therefore, ultraviolet lasers are generally generated by the nonlinear effect frequency conversion method of crystal materials. Therefore, the ultraviolet lasers widely used in the industrial field are mainly solid ultraviolet lasers. laser. 5) By gain medium: solid state (solid, optical fiber, semiconductor, etc.), gas, liquid, free electron laser, etc. Lasers are divided into: ① liquid lasers and gas lasers, due to low efficiency and the need for high-frequency replacement of working materials and maintenance, currently only use their special properties and apply in niche markets; ② current technology of free electron lasers It is not enough. Although it has the advantages of continuously adjustable frequency and wide spectrum range, it is difficult to be widely used in the short term. ③Solid-state lasers are currently the most widely used and have the highest market share. They are usually divided into solid-state lasers with crystals as working materials and fiber lasers with glass fibers as working materials (in the past 20 years, due to the consideration of electro-optical conversion efficiency and beam quality, they have achieved vigorous development. ), currently a small number of lamps such as xenon flash lamps are used as pump sources, and most of them use semiconductor lasers as pump sources. Semiconductor lasers are laser diodes that use semiconductor materials as the laser medium and use current injection into the active region of the diode as the pumping method (light is generated by electron stimulated radiation). It has the characteristics of high electro-optical conversion efficiency, small size and long life. Although it is also a kind of solid-state laser, the light directly generated by semiconductor lasers is limited in the field of direct application due to the poor beam quality. multiple scenes.
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