Design and application of the hottest fiber laser

Design and application of fiber lasers

in the past few years, China's plastic machinery enterprises have increased the development of emerging markets for extruders. Optical devices are widely used in the telecommunications industry, which can make the mean time between failures of high-quality single-mode low-power systems reach about 25 years, ensuring that once the communication technology is installed, it can be done once and for all, and there is no need to worry about it at all. With the collapse of the telecommunications market in the late 1990s, fiber laser manufacturers have shifted their focus to meet the needs of industrial manufacturing, military, medical and aerospace fields. This transformation from telecommunications to other industries requires corresponding high-power and low-power laser technology, focusing on meeting certain operational and performance goals, so as to occupy a part of the market share of laser material processing worth billions. At present, there are a surprising variety of fiber laser technologies on the market, which can meet the needs of various industrial applications. Low power Single-Mode Systems with power levels less than 200W are being increasingly used in microprocessing, marking and medical applications. At the same time, this technology is also developing rapidly towards high power levels without damaging optical fibers. In addition, it also opens up a new world for the application of laser material processing

all manufacturers have introduced fiber laser systems and components. The output power of the commercial product series launched by GSI is as high as 200W, up to 2 kW next year, while the output power of IPG products is less than 10kW. Manufacturers such as IMRA, spectrum physics Inc, synchronous Inc and optigain Inc are mainly engaged in low-power and short pulse fields. Obviously, single-mode fiber lasers have taken the lead in occupying part of the market share of other low-power laser technologies, competing with existing CO2 and lamp pumped nd:yag technologies. This paper will focus on the recent development of high-power fiber laser technology, and discuss what new opportunities the existing relevant technical standards will bring to today's manufacturing industry, which constantly puts forward higher requirements for technology

fiber laser design

high power fiber laser is compact and reliable, which is superior to lamp pumped nd:yag laser in beam quality and power conversion efficiency (about 20%). The fiber laser has one and another latent defect: the long fiber laser cavity (about 12 meters) distributes the pump energy along the whole length direction. High efficiency can reduce thermal management problems, and waste heat can be dissipated along the entire optical fiber. Most rare earth doped silicon fiber lasers are composed of ER or Yb dopants with an output of about 1550nm and 1060nm respectively. Compared with 1550nm output, 1060nm output can achieve higher efficiency. The distribution of transverse electromagnetic modes is controlled by the guided wave characteristics of the core. Narrow optical fibers with a width of tens of microns can achieve single-mode operation, while higher core suppliers need to choose the appropriate material diameter according to material performance, material certification and other requirements to produce higher-order modes

in the process of designing a stable and reliable fiber laser system, a series of other fiber-based components can build a monolithic "all fiber" laser cavity. Other literature has extensively discussed the advantages of all fiber design, two of which are the absence of optical alignment and exposed optical surfaces. The most important of these functional elements are pump combiner and Bragg grating reflector. Figure 1 is the schematic diagram of this kind of fiber laser cavity we designed. The output fiber adopts a single-mode core with a diameter of less than 10 microns, which can ensure high-quality beam output. This architecture aims to generate up to 500W output power in the structure of water-cooled heat sink, and achieve the overall service life of the diode of 100000 hours. At the same time, it can generate up to 120W output power by forced air cooling when the indoor air temperature reaches 35 ℃, and Zhang Jianping can show that the reliability is equivalent to that of the diode

the performance and reliability of fiber laser system depend on the pump laser diode. In the past decade, multi-mode diode pump sources that can generate several watts of output power in the wavelength range of 900 ~ 980nm have been commercially available. Some pump sources have extremely high reliability, and their mean time between failures under normal working conditions has exceeded 500000 hours. Combined with appropriate redundancy, such pump sources with MTBF of more than 100000 hours can be used to build fiber lasers with output power of hundreds of watts

application in micromachining

for micromachining processes that require excellent mode quality and high focusing performance to achieve small body sizes, these new lasers can be commercially applied. For many years, pulsed nd:yag laser has been the first choice for metal precision cutting, precision welding and drilling. At the wavelength of 1 micron, compared with the same carbon dioxide laser, its focusing optical lens is smaller and simpler, and smaller spot size can be achieved. The demand of ultra precision micromachining for more efficient, compact and high beam quality lasers has promoted the rapid growth of fiber laser development. These lasers work near the IR spectral region, have many advantages over traditional lasers, and have greater potential in realizing new micromachining applications

the medical industry is one of the most important application fields of laser micro cutting. Fiber laser is gradually replacing pulse lamp pump nd:yag laser. Medical devices are generally small for the following two basic reasons: first, they usually need to be installed in a narrow area; Second, its production materials are expensive, reducing size means reducing cost. Lasers that can work in areas of only a few microns are ideal solutions for sophisticated and expensive equipment. The most demanding application for micro cutting in the medical equipment industry may be stent cutting. A stent is a slender, lattice shaped metal tube that is permanently inserted into an artery. It helps dilate arteries and dredge blood flow. This cylindrical metal stent inserted into the diseased coronary artery can restore full blood circulation. The materials used for the support include 316L stainless steel or nickel titanium alloy (shape memory alloy). The typical diameter of the tube is 1 ~ 10mm, and the wall thickness is about 100 microns. The key is that the notch width should be small (20 ~ 30 microns), which requires fiber lasers to provide high beam quality and laser power stability. Laser cutting must have high surface quality, small heat affected area and no residue. Figure 2 is the SEM micrograph of a typical scaffold after cutting and cleaning with an ultrasonic cleaner. Ultra high profile accuracy can be achieved by using 100W fiber laser（