Mid-Infrared Laser Sources and Their Applications in Materials Processing

This review focuses on recent advances in mid-infrared (MIR) laser technology in materials processing, with an emphasis on fiber Bragg gratings (FBGs) fabricated by femtosecond lasers. The plane-by-plane femtosecond writing technique enables precise, highly stable FBGs directly within fluoride glass fibers, forming compact, wavelength-selective laser cavities. These advances have led to the development of high-efficiency MIR fiber lasers operating near 2.8–2.92 μm, offering strong material absorption that facilitates cutting, surface modification, and fusion splicing with minimal thermal damage. Polymer and glass materials, which often pose challenges for traditional near-infrared (NIR) lasers, can be processed more effectively with MIR sources. Although FBGs are integral to many MIR laser architectures, certain systems such as 2.92 μm Er:YAP lasers have been realized without FBGs. MIR fiber lasers present a promising platform for photonic manufacturing, addressing the growing demand for precise and efficient processing across a variety of advanced materials. Continued innovations in FBG fabrication, fiber integration techniques, and thermal management are expected to further expand the capabilities and applications of MIR laser technologies.