Applications of high-power 2 m thulium fiber lasers in materials processing

Recent advances in the development of high-power laser sources emitting at the wavelength around 2 mm have enabled a novel material processing regime that is currently finding many new industrial and scientific applications, from automotive manufacturing and biomedical engineering to microelectronics and infrared photonics. High output powers and system reliability enabled by a robust fiber laser architecture bring many new opportunities to laser materials processing community, but also many scientific and technical challenges. On the one hand, a large number of new and unique processes have been introduced, from absorber-free welding of transparent polymers and volume-selective micro-processing of semiconductors to local refractive index modifications in infrared optical materials. On the other hand, with a steadily growing selection of commercially available continuous-wave (CW) and pulsed thulium-doped fiber lasers, processing limits for many conventional laser processing techniques such as cutting, drilling, and welding, will need to be reassessed. In addition, the knowledge of materials' response to irradiation at 2 mm is still incomplete for many important classes of materials, and a limited availability of beam delivery equipment optimized for this wavelength makes industrial implementation of thulium fiber lasers challenging. This chapter is aiming at improved understanding of fundamental principles of light-matter interaction at 2 mm, discusses various new applications, and contributes to implementation of thulium fibers lasers as a promising tool for many industrial areas.