Since the advent of the first solid-state pulsed ruby laser, the development of lasers has been very rapid, and lasers with various working materials and operating modes have continued to appear. Lasers are classified in various ways:
1. According to the operation mode, it is divided into: continuous laser, quasi-continuous laser, pulse laser, and ultra-short pulse laser.
The laser output of the continuous laser is continuous and is widely used in the fields of laser cutting, welding and cladding. Its working characteristic is that the excitation of the working substance and the corresponding laser output can be continued in a continuous manner over a long period of time. Since the overheating effect of the device is often unavoidable during continuous operation, appropriate cooling measures must be taken in most cases.
Pulse laser has a large output power and is suitable for laser marking, cutting, ranging, etc. Its working characteristics include laser energy compression to form narrow pulse width, high peak power, and adjustable repetition frequency, mainly including Q-switching, mode locking, MOPA and other methods. Since the overheating effect and edge chipping effect can be effectively reduced by increasing the single pulse power, it is mostly used in fine processing.
2. According to the working band, it is divided into: infrared laser, visible light laser, ultraviolet laser, and X-ray laser.
Mid-infrared lasers are mainly 10.6um CO2 lasers that are widely used;
Near-infrared lasers are widely used, including 1064~1070nm in the field of laser processing; 1310 and 1550nm in the field of optical fiber communication; 905nm and 1550nm in the field of lidar ranging; 878nm, 976nm, etc. for pump applications;
Since visible light lasers can frequency-double 532nm through 1064nm, 532nm green lasers are widely used in laser processing, medical applications, etc.;
UV lasers mainly include 355nm and 266nm. Since UV is a cold light source, it is mostly used in fine processing, marking, medical applications, etc.
3. According to the working medium, it is divided into: gas laser, fiber laser, solid laser, semiconductor laser, etc.
3.1 Gas lasers mainly include CO2 lasers, which use CO2 gas molecules as the working medium. Their laser wavelengths are 10.6um and 9.6um.
main feature:
-The wavelength is suitable for processing non-metal materials, which makes up for the problem that fiber lasers cannot process non-metals, and has different characteristics from fiber laser processing in the processing field;
-The energy conversion efficiency is about 20%~25%, the continuous output power can reach the level of 104W, the pulse output energy can reach the level of 104 Joules, and the pulse width can be compressed to the nanosecond level;
-The wavelength is right in the atmospheric window and is much less harmful to the human eye than visible light and 1064nm infrared light.
It is widely used in material processing, communications, radar, induced chemical reactions, surgery, etc. It can also be used for laser-induced thermonuclear reactions, laser separation of isotopes, and laser weapons.
3.2 Fiber laser refers to a laser that uses rare earth element-doped glass fiber as the gain medium. Because of its superior performance and characteristics, as well as cost advantages, it is currently the most widely used laser. Features are as follows:
(1) Good beam quality: The waveguide structure of the optical fiber determines that the fiber laser is easy to obtain single transverse mode output, is little affected by external factors, and can achieve high-brightness laser output.
(2) The output laser has many wavelengths: This is because the energy levels of rare earth ions are very rich and there are many types of rare earth ions;
(3) High efficiency: The overall electro-optical efficiency of commercial fiber lasers is as high as 25%, which is beneficial to cost reduction, energy conservation and environmental protection.
(4) Good heat dissipation characteristics: glass material has an extremely low volume-to-area ratio, fast heat dissipation, and low loss, so the conversion efficiency is high and the laser threshold is low;
(5) Compact structure and high reliability: There is no optical lens in the resonant cavity, which has the advantages of adjustment-free, maintenance-free and high stability, which is unmatched by traditional lasers;
(6) Low manufacturing cost: Glass optical fiber has low manufacturing cost, mature technology and the advantages of miniaturization and intensification brought about by the windability of the optical fiber.
Fiber lasers have a wide range of applications, including laser fiber communications, laser space long-distance communications, industrial shipbuilding, automobile manufacturing, laser engraving, laser marking, laser cutting, printing rollers, military defense and security, medical equipment and equipment, and as pumps for other lasers Pu Yuan and so on.
3.3 The working medium of solid-state lasers is insulating crystals, which are generally excited by optical pumping.
YAG lasers (rubidium-doped yttrium aluminum garnet crystal) commonly use krypton or xenon lamps as pump lamps, because only a few specific wavelengths of pump light will be absorbed by Nd ions, and most of the energy will be converted into heat energy. Usually YAG Laser energy conversion efficiency is low. And the slow processing speed is gradually replaced by fiber lasers.
New solid-state laser, a high-power solid-state laser pumped by a semiconductor laser. The advantages are high energy conversion efficiency, the electro-optical conversion efficiency of semiconductor lasers is as high as 50%, which is much higher than that of flash lamps; the reactive heat generated during operation is small, the medium temperature is stable, and it can be made into a fully cured device, eliminating the influence of vibration, and the laser spectrum line is narrower , better frequency stability; long life, simple structure and easy to use.
The main advantage of solid-state lasers over fiber lasers is that the single pulse energy is higher. Combined with ultra-short pulse modulation, the continuous power is generally above 100W, and the peak pulse power can be as high as 109W. However, because the preparation of the working medium is more complicated, it is more expensive.
The main wavelength is 1064nm near-infrared, and 532nm solid-state laser, 355nm solid-state laser, and 266nm solid-state laser can be obtained through frequency doubling.
3.4 Semiconductor laser, also known as laser diode, is a laser that uses semiconductor materials as its working substance.
Semiconductor lasers do not require complex resonant cavity structures, so they are very suitable for miniaturization and lightweight needs. Its photoelectric conversion rate is high, its life is long, and it does not require maintenance. It is often used in pointing, display, communication ranging and other occasions. It is also often used as a pump source for other lasers. Laser diodes, laser pointers and other familiar products all use semiconductor lasers.