Development and application of semiconductor laser industry

　　Semiconductor lasers are commonly known as laser diodes. They are called semiconductor lasers because they use semiconductor materials as working materials . Semiconductor lasers are composed of fiber-coupled semiconductor laser modules, beam combining devices, laser energy transmission cables, power systems, control systems, and mechanical structures. Laser output is achieved under the drive and monitoring of the power system and control system. Let's learn about the relevant content with the editor of Industrial Control.

　  1. Introduction to Semiconductor Lasers

　　Semiconductor lasers are commonly known as laser diodes. They are called semiconductor lasers because they use semiconductor materials as working materials . Semiconductor lasers are composed of fiber-coupled semiconductor laser modules, beam combining devices, laser energy transmission cables, power systems, control systems and mechanical structures. Laser output is achieved under the drive and monitoring of the power system and control system. The common working materials of semiconductor lasers are mainly gallium arsenide (GaAs), cadmium sulfide (CdS), indium phosphide (InP), zinc sulfide (ZnS), etc. There are three main excitation methods according to different working materials: electrical injection, pump type and high-energy electron beam excitation.

　　(1) Electrical injection is a semiconductor laser, which is generally made of working materials such as GaAS, CdS, InP, ZnS, etc. as the main materials to form a semiconductor junction diode. When subjected to electrical injection, the current injected along the forward bias voltage excites the working material, thereby generating stimulated emission in the junction plane area.

　　(2) Punp lasers are generally made of a germanium single crystal (P-type semiconductor single crystal) with holes as carriers or a germanium single crystal (N-type semiconductor single crystal) with electrons as carriers doped with acceptor impurities as the working material, and are pumped by lasers emitted by other lasers to achieve population inversion.

　　(3) High-energy electron beam excited semiconductor lasers are generally similar to pump lasers in the selection of working materials, and also use semiconductor germanium single crystals. However, it is worth noting that the selection of P-type semiconductor single crystals for high-energy electron beam excited semiconductor lasers is mainly based on PbS, CbS and ZnO.

　　There are many types of semiconductor lasers, and there are many ways to classify them according to their chip parameters and packaging methods. Among them, the classification methods of semiconductor lasers with fiber output are mainly as follows:

　　Figure 1 Classification of semiconductor lasers

　　2. Development of semiconductor laser technology

　　Since the invention of the world's first semiconductor laser in 1962, semiconductor lasers have undergone tremendous changes and have greatly promoted the development of other science and technology.

　　In recent years, low-power semiconductor lasers used in the field of information technology have developed rapidly, such as DFB and dynamic single-mode laser diodes used in optical fiber communications, visible light wavelength laser diodes widely used in optical disk processing, and even ultra-short pulse laser diodes, which have made substantial innovative progress.

　　Low-power laser diodes also have the characteristics of high integration, high speed and tunability. The development speed of large-scale high-power semiconductor lasers is also accelerating.

　　In the 1980s, the output power of independent laser diodes was already above 100mW, and the conversion efficiency reached 39%. In the 1990s, Americans once again raised the indicator to a new level, reaching a conversion efficiency of 45%. In terms of output power, it also changed from W to KW level.

　　At present, with the support of research projects, laser technologies such as semiconductor laser chip structure, epitaxial growth and device packaging have made great progress, and the performance of unit devices has also achieved major breakthroughs: electro-optical conversion efficiency is over 70%, the beam divergence angle is very low, the continuous output power of a single bar exceeds kilowatts, and the use of carbon nanometer (CN) heat sinks can increase the cooling efficiency of lasers by 30% compared with traditional semiconductor bar installation technology. The output power of a single tube with a bar width of 100μm reaches 24.6W, and the high-power continuous working life is as long as tens of thousands of hours.

　　High-efficiency and high-power semiconductor lasers have also rapidly developed into all-solid-state lasers, thus giving LDP solid-state lasers new development opportunities and prospects.

　　3. Semiconductor Laser Market Size

　　Semiconductor lasers have the advantages of small size, light weight, long life, high operational reliability, low energy consumption, high electro-optical conversion efficiency, easy large-scale production and low price. They are widely used in CD laser players, fiber optic communications, optical storage, laser printers, etc., covering the entire field of optoelectronics.

　　With the continuous development and breakthrough of technology, semiconductor lasers are developing in the direction of shorter emission wavelength, higher emission power, ultra-small size and long life to meet the needs of various applications, and the product variety is becoming increasingly rich. It has also been widely used in laser processing, 3D printing, laser radar, laser ranging, military, medical and life sciences. In addition, by coupling into optical fiber for transmission, high-power direct semiconductor lasers have been widely used in the fields of cutting and welding.

　　At present, the global semiconductor laser market is large, with an increase in value from US$3.54 billion in 2012 to US$5.31 billion in 2017, with a compound annual growth rate of 8.4%.

　　Figure 2 Global semiconductor laser market size and growth rate from 2012 to 2017 (Unit: 100 million US dollars)

　　4. Application of semiconductor lasers

　　1. Application of semiconductor lasers in optoelectronics

　　(1) Fiber-optic communication. Semiconductor lasers are the only practical light source for fiber-optic communication systems, and fiber-optic communication has become the mainstream of contemporary communication technology.

　　(2) Optical disc access. Semiconductor lasers have been used in optical disc storage. Their greatest advantage is that they can store a large amount of sound, text, and image information. The use of blue and green lasers can greatly increase the storage density of optical discs.

　　(3) Spectral analysis. Far-infrared tunable semiconductor lasers have been used for environmental gas analysis, monitoring of air pollution, automobile exhaust, etc. In industry, they can be used to monitor the process of vapor deposition.

　　(4) Optical information processing. Semiconductor lasers have been used in optical information processing systems. Two-dimensional arrays of surface-emitting semiconductor lasers are ideal light sources for optical parallel processing systems and will be used in computers and optical neural networks. 5) Laser microprocessing. With the help of high-energy ultrashort light pulses generated by Q-switched semiconductor lasers, integrated circuits can be cut and punched.

　　(5) Laser alarm. Semiconductor laser alarms have a wide range of uses, including anti-theft alarms, water level alarms, vehicle distance alarms, etc.

　　(6) Laser printers. High-power semiconductor lasers have been used in laser printers. The use of blue and green lasers can greatly improve printing speed and resolution.

　　(7) Laser barcode scanner. Semiconductor laser barcode scanners have been widely used in the sale of goods and the management of books and archives.

　　8) High-definition laser TV. In the near future, semiconductor laser TVs without cathode ray tubes will be available on the market. They use red, blue and green lasers and are estimated to consume 20% less power than existing TVs.

　　2. Application of semiconductor lasers in material processing

　　Semiconductor lasers are mostly used for material cutting and circuit board processing. Due to the high stability and high efficiency of lasers, they can easily and accurately cut industrial materials, and low-wavelength ultraviolet lasers are also well used in the processing of high-frequency circuit boards.

　　(1) Pump sources for fiber lasers and solid-state lasers

　　At present, the largest application of semiconductor lasers is as pump sources for fiber lasers and solid-state lasers. As a pump source for fiber lasers, increasing the unit power of semiconductor lasers can fundamentally simplify the structure of the pump system or increase the pump power level. As the output power of fiber lasers and solid-state lasers increases, higher requirements are also placed on the power of semiconductor pump sources.

　　(2) Metal cutting

　　Due to the limitation of beam quality, traditional semiconductor lasers are difficult to be used directly for metal cutting. In recent years, with the improvement of semiconductor coupling technology and the gradual maturity of new beam combining technology, some semiconductor lasers with fiber output above kilowatt level can meet the beam quality requirements of cutting. In addition, due to the diversity of semiconductor laser wavelengths, the wavelength of short-wavelength semiconductor lasers is very close to the maximum wavelength absorption of aluminum. In the automotive industry, high-power semiconductor lasers are very suitable for welding aluminum materials for car bodies. Semiconductor lasers with laser output powers of 2KW to 6KW have been widely used in the production process of the automotive industry.

　　(3) Plastic welding

　　Laser welding using small and medium power semiconductor lasers improves the traditional methods of thermoplastic welding. For example, ultrasonic welding can directly plasticize the connection area before pressing. Laser can achieve light-penetrating laser welding, forming a uniform melt in the connection area and avoiding the fuzzing caused by friction. Semiconductor laser plastic welding is widely used in the sealing welding of sensors or plastic boxes in the automotive industry, and can also be used for the edging of wooden products or the processing of fiber-reinforced synthetic materials.

　　(4) Laser cladding

　　Laser cladding, also known as laser cladding or laser melting, is a surface modification technology that forms a metallurgically bonded cladding layer on the surface of the base material by adding cladding material to the surface of the base material and using a high-energy-density laser beam to melt it together with a thin layer on the surface of the base material. Semiconductor lasers can be used in the cladding process to reduce the mixing of powder and collective materials and reduce heat input, further improving the economic benefits of the cladding process.

　　(5) Laser soldering

　　Soldering is a welding method that uses low-melting-point metal solder to melt and then penetrate and fill the gaps at the joints of metal parts. The solder is usually a tin-based alloy. At present, semiconductor lasers with an output power of 100W have been promoted and applied in soldering. With the further reduction of semiconductor laser prices, the continuous increase in labor costs, and the advancement of intelligent manufacturing and precision manufacturing, it is expected that laser soldering will gradually replace traditional soldering irons in the future and be widely used.

　　3. Application of semiconductor lasers in military

　　Low-power semiconductor lasers are widely used in laser guidance and laser ranging due to their small size, long life and easy modulation. They are simple and easy to use, and have achieved good results. The development of high-power semiconductor lasers has also made them shine in the military field, and laser radar, laser simulation and deep-sea optical communications have all been greatly developed.

　　The military applications of semiconductor lasers mainly include: high-energy laser weapon pump sources, high-power semiconductor laser beam combination and direct application; laser guidance, which allows missiles to fly in the laser beam until they destroy the target. Semiconductor laser guidance is mostly used for surface-to-air missiles, air-to-air missiles, surface-to-surface missiles, etc.; laser ranging, which is mainly used in anti-tank weapons and aviation, aerospace and other fields; laser radar, which is used to monitor targets, accurately locate incoming targets, and track terrain for helicopters and cruise missiles, etc. Guidance and ranging applications are mainly based on high-power pulsed semiconductor lasers, with wavelengths concentrated around 904nm. In recent years, based on human eye safety considerations, there has been a trend towards longer wavelengths.

    The above is an introduction to the development and application of semiconductor laser industry in industrial control. If you want to know more related information, please pay more attention to eeworld. eeworld Electronic Engineering will provide you with more complete, detailed and updated information.