1. Classification by working material According to the different state of the working material, all lasers can be divided into the following categories: ①Solid-state lasers (crystal and glass), the working material used in this type of laser can be excited by Radiation metal ions are doped into a crystal or glass matrix to form a luminescent center; ②Gas lasers, the working material they use is gas, and according to the nature of the working particles that actually produce stimulated emission in the gas, It is further divided into atomic gas lasers, ion gas lasers, molecular gas lasers, excimer gas lasers, etc.; ③Liquid lasers, the working materials used in this type of lasers mainly include two types, one is organic fluorescent dye solution, the other is It is an inorganic compound solution containing rare earth metal ions, in which metal ions (such as Nd) act as working particles, and inorganic compound liquids (such as SeOCl) act as a matrix; ④Semiconductor lasers, which are based on certain semiconductor materials The working substance produces stimulated emission. The principle is that through a certain excitation method (electric injection, optical pump or high-energy electron beam injection), between the energy band of the semiconductor material or between the energy band and the impurity energy level, through the excitation of non- Balance the carrier and realize the population inversion, thereby generating the stimulated emission of light; ⑤free electron laser, this is a special type of new laser, the working substance is the directional free electron moving at high speed in the spatially changing magnetic field Beam, as long as the speed of the free electron beam is changed, tunable coherent electromagnetic radiation can be generated. In principle, the coherent radiation spectrum can transition from the X-ray band to the microwave region, so it has a very attractive prospect; ⑥Fiber laser, which refers to Lasers that use rare-earth-doped glass fibers as gain media can be developed on the basis of fiber amplifiers: high power density is easily formed in the fiber under the action of the pump light, resulting in the laser energy level of the laser working material. The number is reversed. When a positive feedback loop (to form a resonant cavity) is properly added, the laser oscillation output can be formed. 2. Classification by excitation mode ①Optical pump lasers. Refers to lasers excited by optical pumps, including almost all solid-state lasers And liquid lasers, as well as a few gas lasers and semiconductor lasers. ②Electrically excited lasers. Most gas lasers are excited by gas discharge (DC discharge, AC discharge, pulse discharge, electron beam injection), and the common semiconductor Lasers are mostly excited by junction current injection, and some semiconductor lasers can also be excited by high-energy electron beam injection. ③Chemical lasers. This refers specifically to lasers that use energy released by chemical reactions to excite working materials. The chemical reaction can be induced by light, discharge and chemical respectively. ④Nuclear pump laser. Refers to a type that uses the energy released by a small nuclear fission reaction to excite working materials. Special lasers, such as nuclear-pumped helium-argon lasers, etc. 3. Classification by operation mode Because of the different working materials, excitation methods and application purposes of the laser, the operation mode and working state are also different, which can be divided into the following main types. ① Continuous laser, its working characteristic is the excitation of the working material and the corresponding laser display, which can be continuously carried out in a continuous manner over a long period of time. The solid-state laser excited by the continuous light source and the gas laser working in the continuous electrical excitation mode And semiconductor lasers fall into this category. Since the overheating effect of the device is inevitably produced during continuous operation, it is necessary to take appropriate cooling measures in most cases. ②Single pulse laser. For this type of laser, the excitation of the working material and the corresponding laser emission are both a single pulse process in terms of time. General solid lasers, liquid lasers and some special gas lasers, All of them are operated in this way. At this time, the thermal effect of the device can be ignored, so special cooling measures may not be taken. (See www.gnlaser.com for the details edited by laser cutting machine above) ③Repetitive pulse laser, this type of device is characterized by a series of repetitive laser pulses. For this reason, the device can be excited by repetitive pulses. Or the excitation is carried out in a continuous manner but the laser oscillation process is modulated in a certain way to obtain a repetitive pulse laser display, which usually requires effective cooling measures for the device.