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Laser Machining of Metals
Published in V. K. Jain, Advanced Machining Science, 2023
It has been six decades since the invention of lasers. The machine tool industry has slowly replaced conventional machining processes with laser-based processes. The last decade has seen a dramatic rise in the use of lasers in machining, driven by the development of fiber lasers and their ability to deliver a laser beam conveniently using fiber optics. However, the effective application of lasers in machining requires a great deal of understanding of its several process parameters. Laser interaction with matter is very complex and depends on the pulse duration and laser intensities. Material removal is usually followed by the formation of an intense plasma, which can further interact with the laser and makes the process phenomena even more complex. The use of physics-based models is seen as an approach to optimize the process mainly because of the small length scales and short time scales at which it happens. Laser interaction with matter is highly non-linear with picosecond and femtosecond pulses. This still continues to attract the attention of many researchers to understand the physics of the process. Due to the complex nature of the laser beam machining process, future research in laser beam machining could be driven by the use of data-driven models for process optimization. The breakthrough in laser machining could be in the use of machine-learning algorithms. This could pave the way for creating smart laser beam machining systems.
Novel Mode-Locked Fiber Lasers with Broadband Saturable Absorbers
Published in Sam Zhang, Jyh-Ming Ting, Wan-Yu Wu, Functional Thin Films Technology, 2021
The fiber laser is arguably one of the greatest inventions of the 20th century. The fiber laser has greatly improved people’s lives and promoted social progress. T. H. Maiman produced the world’s first solid-state laser in 1960, and then, fiber lasers were also proposed [1–4]. In the 1980s, the emergence of diode pump lasers brought a new generation of fiber lasers with the advantages of intense and fast heat dissipation, low loss, and high conversion efficiency. Also, the characteristic high output power reaches the order of 10,000 W, which makes the application of fiber lasers suitable in various fields. Depending on the different rare-earth ions that are doped in fiber lasers, the working wavelengths of the lasers cover the wavelength range from near infrared to mid-far infrared [5–8]. Among these lasers, the mid-infrared laser can affect the vibrational energy spectrum of most gases and organic molecules, and it is often used in precision laser spectroscopy, identification of gas, and organic molecular structure dynamics. Lasers also play an irreplaceable role in the fields of lidar, industrial manufacturing, laser-marking welding, molecular optical spectroscopy, laser medical treatment, environmental monitoring, military countermeasures, space communications, semiconductor micromachining, and terahertz generation.
Ultrafast Fiber Lasers
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
A fiber laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, and thulium. Fiber nonlinearities, such as stimulated Raman scattering or four wave mixing, can also provide gain and thus serve in effect as gain media. Unlike most other types of lasers, the laser cavity in a fiber laser is constructed monolithically by fusion splicing the different types of fibers; most notably fiber Bragg gratings replace conventional dielectric mirrors to provide optical feedback. To pump fiber lasers, semiconductor laser diodes or other fiber lasers are used almost exclusively. Fiber lasers can have several-kilometers-long active regions and provide very high optical gain. They can support kilowatt level continuous output power because the fiber’s high surface area-to-volume ratio allows efficient cooling. The fiber waveguiding properties reduce or remove completely thermal distortion of the optical path, thus resulting in typically diffraction-limited high-quality optical beams. Fiber lasers also feature compact layout compared to rod or gas lasers of comparable power, as the fiber can be bent to small diameters and coiled. Other advantages include high vibrational stability, extended lifetime, and maintenance-free turnkey operation.
Fiber laser microcutting on duplex steel: parameter optimization by TOPSIS
Published in Materials and Manufacturing Processes, 2022
C Gopinath, Poovazhagan Lakshmanan, Sarangapani Palani
The schematic diagram of a fiber laser cutting (FLC) machine is presented in the Fig. 1(a). The FLC has four main units, which include source unit, control system unit, cooling unit, and workstation. The workstation controls the three-axis motion and alignment of the work piece in the FLC process. The machining factors are controlled by the integrated computer in the FLC system. The FLC machine used in this work is yttrium-doped optical fiber laser MLS20. The machine operates with a power of 20 W, a wavelength of 1064 nm, and a frequency of 60 kHz. Generally, fiber laser uses an optical fiber to generate and transmit photons. The DSS2205 sheet of size 50 mm × 50 mm × 0.44 mm was chosen as the work material. Figure 1(b) displays the DSS2205 work sample with microholes cut on it by a FLC machine with a 100 µm spot beam diameter.
Optimizing the pump wavelength to improve the transverse mode instability threshold of fiber laser by 3.45 times
Published in Journal of Modern Optics, 2021
Yingchao Wan, Baolai Yang, Peng Wang, Xiaoming Xi, Hanwei Zhang, Xiaolin Wang
Fiber lasers are widely used in industrial processing, biological medical treatment, fundamental research and other fields due to their excellent beam quality, flexible operation, convenient thermal management, compact structure and other advantages [1–3]. For the past two decades, with the progress of the high brightness pump source and the technological level of various fiber devices, the power of fiber lasers has been rapidly improved [4–6]. However, transverse mode instability (TMI) in fiber lasers has been recently found to present a serious limiting for the power scaling in a good-quality laser beam [7]. TMI refers to the phenomenon that the output laser mode changes abruptly when the laser power exceeds a certain threshold value and causes beam quality degradation [8]. It is generally believed that the TMI is the mode coupling caused by the thermally induced refractive index grating caused by the quantum defect and other thermal effects in the laser conversion process, which is also a kind of TMI phenomenon that has been widely studied at present [9–11]. When TMI appears, the fiber laser will come out the decrease of optical-to-optical (O-O) conversion efficiency, the abnormal temperature increase of the cladding stripper and the fluctuation in the time–frequency domain, which may destroy the normal operation of the laser.
Effect of additives on a surface textured piston ring–cylinder liner system
Published in Tribology - Materials, Surfaces & Interfaces, 2019
Several techniques have been used to create a texture pattern, such as Photochemical texturing [18], abrasive jet machining [19,20], embossing [21], and Laser surface texturing (LST). Among all the techniques, the LST method is the most commonly used technique to form a texturing pattern of required shapes and sizes. LST is mostly carried out using Nd3 +: YAG laser system. However, the fibre laser system has certain advantages over Nd3 +: YAG laser system. In the fibre laser system, the laser is generated within a fibre and hence mirror alignment is not required. The service life of a fibre laser system is around 25,000 laser hours. While, Nd3 +: YAG laser system comprises of expensive pump diodes, which need to be replaced after 8000 to 15000 laser hours. However, beam quality of Nd3 +: YAG laser is better than fibre laser.