Lasers are another major invention of mankind since the 20th century, following nuclear energy, computers, and semiconductors. They are characterized by high brightness, pure color, and high energy, and are known as "the fastest knife", "the most accurate ruler", and "the brightest light". They are widely used in marking, welding, cutting and other fields. A laser is a component used to generate laser light and is the core component in laser equipment. The value of a laser accounts for 20%-40% of the total value of a complete set of laser processing equipment, or even higher. So, what are the types of lasers? What are the different applications of different types of lasers? 1. Types of Lasers There are many types of lasers, with various classification standards, but the most common ones are based on gain medium, operation mode, pumping method, and output wavelength. According to the different gain media, lasers can be divided into solid-state, gas, liquid lasers, etc. From these types, different lasers have different performance characteristics, but solid-state lasers have more significant advantages. Solid-state lasers have good stability, high power, low later maintenance costs, and a wide range of application scenarios. Liquid lasers have a large adjustable range of laser wavelengths, but their low power upper limit and high maintenance costs limit their large-scale application; gas lasers are difficult to achieve high-power output, and their application space is difficult to expand continuously. Let's take a look at the specific classifications. (1) Solid-state lasers are generally small in size, robust, have high pulsed radiation power, and have a wide range of applications. For example: Nd:YAG lasers. Nd (neodymium) is a rare earth element, and YAG stands for yttrium aluminum garnet, whose crystal structure is similar to that of ruby. There are also Tm:YAG, Ho:YAG, and so on. (2) Semiconductor lasers are small in size, light in weight, long in service life, and simple in structure, making them particularly suitable for use in airplanes, warships, vehicles, and spacecraft. The wavelength of semiconductor lasers can be changed by external electric fields, magnetic fields, temperature, pressure, etc., and they can directly convert electrical energy into laser energy, so they have developed rapidly. (3) Gas lasers are those that generate coherent light by releasing electric current through gas. They have good monochromaticity and coherence, with laser wavelengths reaching thousands of types, and are widely used. Gas lasers have simple structures, low cost, and easy operation. They are widely used in industry, agriculture, medicine, precision measurement, holography, and other fields. Gas lasers have various excitation methods such as electrical energy, thermal energy, chemical energy, light energy, and nuclear energy. (4) Dye lasers, which use liquid dyes as the working substance, came out in 1966 and are widely used in various scientific research fields. At present, about 500 kinds of dyes that can generate lasers have been found. These dyes can be dissolved in alcohol, benzene, acetone, water, or other solutions. They can also be contained in organic plastics to appear in solid form or sublimated into vapor to appear in gaseous form. Therefore, dye lasers are also called "liquid lasers". The prominent feature of dye lasers is that their wavelengths are continuously adjustable. There are many types of dye lasers, which are low in price, high in efficiency, and their output power can be comparable to that of gas and solid-state lasers. They are used in spectroscopic spectroscopy, photochemistry, medical treatment, and agriculture. (5) Chemical lasers: Some chemical reactions produce enough high-energy atoms, which can release large energy and be used to generate laser action. This is mainly used in weapons. For example, hydrogen fluoride lasers can provide continuous output power in the megawatt range. (6) Free electron lasers are more suitable for generating high-power radiation than other types. Their working mechanism is different: they obtain high-energy electron beams of tens of millions of volts from accelerators, and form energy levels of different energy states through periodic magnetic fields to generate stimulated radiation. (7) Excimer lasers (which actually belong to gas lasers) are ultraviolet gaseous lasers. Lasers generated when molecules formed by a mixture of excited inert gases and another gas (inert gas or halogen) transition to their ground state are called excimer lasers. Excimer lasers are low-energy lasers with no thermal effect. They are pulsed lasers with strong directionality, high wavelength purity, and high output power. The photon energy wavelength range is 157-353 nanometers, and the pulse time is tens of nanoseconds, belonging to ultraviolet light. The most common wavelengths are 157 nm, 193 nm, 248 nm, 308 nm, and 351-353 nm. (8) Fiber lasers use gain media (rare earth elements) in optical fibers to provide amplification of optical signals. There are two types of fiber lasers: single-end pumped and double-end pumped, and the latter can achieve higher output power. The coherent synthesis technology under research can further expand the output power. (8) Classified by continuity, there are continuous lasers and pulsed lasers (Pulsed laser and Ultrashort pulsed laser). Pulsed lasers include nanosecond (10e-6 seconds), picosecond (10e-9 seconds), femtosecond (10e-12 seconds), and even attosecond (10e-15 seconds) lasers. Continuous lasers, longer pulsed lasers, and ultrashort pulsed lasers have very different thermal effects when acting on the target surface. (9) Quantum dot lasers are semiconductor lasers with a three-dimensional quantum confinement structure for injected carriers. Quantum dot lasers have the characteristics of high output spectral purity, high conversion efficiency, low threshold current, strong interference, high modulation rate, good temperature stability, excellent anti-reflection, and high communication confidentiality. Their comprehensive performance is better than that of traditional semiconductor lasers, as well as quantum well lasers and quantum wire lasers. They have great application prospects and can play an important role in new-generation optical communication technology and optical interconnection technology. (10) There are many other types of lasers, such as Raman lasers, metal-vapor lasers, etc. For different applications, there will be many subdivided technologies. As the foundation of Industry 4.0, lasers will play an increasingly important role. So, what are the specific applications of these lasers in modern industry and technology? Let's briefly talk about the applications of solid-state lasers, semiconductor lasers, quantum dot lasers, and fiber lasers. 2. Applications of Different Lasers Solid-state Lasers The gain medium of solid-state lasers is laser crystals or doped glass. It is the earliest type of laser. Since the first ruby laser was born in 1960, more than 60 years have passed, and today its technology has basically matured. Moreover, its wavelength coverage is wide, basically covering from ultraviolet to infrared. Benefiting from the wide wavelength selection range, as well as the advantages of narrow pulse width and high peak power, solid-state lasers are widely used in micro-nano processing fields (with processing accuracy reaching the micron and nanometer levels). However, domestic solid-state lasers started relatively late, and due to factors such as technological development constraints, their large-scale application is relatively limited, mostly used in cutting-edge scientific research in environmental, medical, military and other fields. Semiconductor Lasers Semiconductor lasers can be widely used in military and civilian fields, such as communication, display, storage, energy, laser processing, instruments and meters, radar, weapons, etc., and the market scale continues to expand. It is estimated that from 2020 to 2025, the global semiconductor laser market will grow at a compound annual growth rate of about 9.6%, and the market scale will reach more than 25.1 billion yuan by 2025. China's semiconductor laser market is developing rapidly, with demand growing faster than the global average. Quantum Dot Lasers According to the "2022-2026 Quantum Dot Laser Industry In-depth Market Research and Investment Strategy Suggestions Report" released by the New Thinking Industry Research Center, with the rapid development of information technology, the market's requirements for information transmission capacity and transmission security are constantly increasing, and the industrial field's requirements for the photoelectric conversion efficiency and energy consumption of lasers are also rising. In high-end fields, traditional semiconductor lasers can no longer meet the demand, and new quantum dot lasers with better performance have attracted attention. Quantum dot lasers can be used in high-speed optical communication, quantum communication, flat panel display, industrial manufacturing, laser weapons and other fields, especially in quantum communication, where quantum dot lasers play an important role and are expected to replace traditional semiconductor lasers in the future. In terms of quantum dot laser research, China's quantum dot research is at the international advanced level. As early as 2003, researchers from the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, had mastered an effective method to control the laser wavelength in the range of 800-1300 nanometers and developed a temperature-continuous lasing quantum dot laser. In addition to China, in 2019, scientists from Nanyang Technological University in Singapore developed a method to make colloidal quantum dots generate lasers under the action of an electric field; in 2020, a research team from the University of California, Santa Barbara, USA, prepared Si-based quantum dot lasers by growing a GaAs buffer layer directly on a Si substrate using the MOCVD method. Analysts from New Thinking Industry said that in terms of the industrialization development of quantum dot lasers, at present, Huagong Tech is in a leading position in China's market, with the qualification for industrialized production of quantum dot lasers, and its subsidiary Huagong Zhengyuan has an independent semiconductor quantum dot laser chip production line. Due to high technical barriers, at this stage, the number of quantum dot laser manufacturers in China and the global market is small. With the continuous expansion of the quantum communication industry scale, these leading enterprises will have great development space in the future. Fiber Lasers Fiber lasers use doped optical fibers as the gain medium. They have many advantages such as good beam quality, high output power, good heat dissipation, excellent stability, small weight and volume, simple structure, and easy industrial production. They are the optimal solution for most laser application fields at present, mainly used in macro processing fields (generally processing with a scale of more than millimeters). The various advantages of fiber lasers have brought them a wide range of downstream application spaces. They have been widely used in industrial fields such as marking, cutting, and welding, and are gradually replacing other lasers. Specifically, their applications are as follows. Automotive Industry In the automotive industry, laser technology is mainly used for body tailor-welding, welding, and component welding. Laser tailor-welding refers to, in the design and manufacturing of car bodies, selecting steel plates of different specifications according to different design and performance requirements of the car body, and completing the manufacturing of a certain part of the car body through laser cutting and assembly technology, such as the front windshield frame, door inner panel, body floor, center pillar, etc. Laser tailor-welding has the advantages of reducing the number of parts and molds, reducing the number of spot welds, optimizing material usage, reducing part weight, lowering costs, and improving dimensional accuracy, and has been adopted by many major automobile manufacturers and parts suppliers. Laser welding is mainly used for welding the body frame structure, such as the welding of the roof and the side body. The traditional resistance spot welding method has gradually been replaced by laser welding. With laser welding technology, the width of the joint surface between workpieces can be reduced, which not only reduces the amount of sheet metal used but also improves the rigidity of the car body. When laser welding components, there is almost no deformation at the welding part, the welding speed is fast, and no post-welding heat treatment is required. Laser-welded components have been widely used, commonly in transmission gears, valve tappets, door hinges, etc. Aerospace In the manufacturing of aerospace equipment, the shell is made of special metal materials with high strength, high hardness, and high temperature resistance. Ordinary cutting methods are difficult to process the materials, and laser cutting is an efficient processing method. It can be used to cut and process aircraft skins, honeycomb structures, frames, wing spars, tail fairings, helicopter main rotors, engine casings, and flame cylinders. Due to the characteristics of high precision, fast processing speed, small thermal impact, and no mechanical effect, laser cutting is applied in many aspects of aero-engine manufacturing. From the air intake to the exhaust nozzle of modern aero-engines, laser cutting technology is needed. The adoption of modern laser cutting technology has solved many problems such as the cutting of difficult-to-process materials for aero-engines, the efficient processing of large thin-walled parts with group holes, the high-precision cutting of part blade holes, and the processing of special surface parts. It has effectively promoted the development of modern aerospace vehicles towards high performance, lightweight, long life, short cycle, low cost, etc., and added a lot of impetus to the development of the modern aerospace industry. For a long time, the connection between aircraft structural parts has been using the backward riveting process, mainly because the aluminum alloy materials used in aircraft structures are heat-treated strengthened aluminum alloys (i.e., high-strength aluminum alloys). Once fusion welded, the heat treatment strengthening effect will be lost, and intergranular cracks are difficult to avoid. The adoption of laser welding technology has overcome such problems, greatly simplified the manufacturing process of the aircraft fuselage, significantly reduced the fuselage weight and cost, and laser welding technology is a technological revolution in the aircraft manufacturing industry. Sheet Metal Processing The sheet metal industry is one of the most important application markets for laser processing, and the transformation of processing technology is imperative, which provides a broad space for the application of laser cutting machines, laser welding machines, laser marking machines and other laser equipment in the sheet metal industry. Most manufacturing industries involve sheet metal processing, such as machinery, electrical, instruments, kitchen and bathroom, etc. Therefore, fiber lasers play an important role in the sheet metal industry. Laser cutting machines are a technological revolution in sheet metal processing and one of the common means of sheet metal processing at present. Laser cutting machines have high flexibility, fast cutting speed, high production efficiency, and short product production cycle, which have won a broad market for customers. At present, most of the processing in the medium and thin plate fields on the market uses fiber laser cutting machines. Their characteristics of high efficiency and high precision make them widely praised, and they have even replaced part of the plasma and flame markets in the thick plate field. With the increasing requirements for welding strength and appearance of sheet metal welding, especially for parts with high added value and high welding quality requirements, traditional welding methods will inevitably bring problems such as workpiece deformation due to large heat input, requiring a lot of grinding and forming methods, leading to increased costs. Laser welding has extremely high energy density and extremely low heat-affected zone, which not only significantly improves welding efficiency but also improves quality and reduces post-processing time. Therefore, the application of laser welding in modern sheet metal manufacturing is becoming more and more popular. Conclusion With excellent comprehensive performance, fiber lasers have quickly achieved volume growth in the industrial laser market and now occupy more than half of the industrial laser market. With the continuous development of traditional substitution and emerging application scenarios, the global market share of fiber lasers is expected to further increase. Source: Industry Observation, Fiber Upgrade, New Thinking Network