Over the past 50 years, fiber lasers have seen progressive development, which has promoted scientific and technological advances in a wide range of areas. The attractive characteristics of fiber lasers, including compactness, easy thermal management, reliable beam quality, low cost of maintenance, and so forth, facilitate their applications in telecommunications, environmental monitoring, medical diagnosis and treatment, material processing, and defense. The extensive research and development on fiber lasers, therefore, make a lasting impact on our daily life.

The performance improvement on fiber lasers with regard to the operating wavelength range, laser output power, temporal and spatial evolution, and practical integration with compact system design has been driven by the joint developments in fiber materials, laser system design, and applications. New host material glasses, such as fluoride, tellurite, and chalcogenide glasses, have been developed to extend the operating wavelength of fiber lasers from near infrared to mid-infrared. Nonlinear processes, such as four-wave mixing, have been employed for harmonic generation in fiber systems, allowing for the achievement of wavelength inaccessible by conventional laser technology. On the other hand, the nonlinear effects, such as SBS and SRS, are still the dominant limitation toward high power fiber amplifiers, where different strategies have been proposed to break through the bottleneck. Intensive investigation on coherent beam combining provides substantial potential in brightness and power scaling. This feature issue focuses on some of the most recent advances in fiber lasers and their applications. The feature will bring together new achievements on fiber lasers, ranging from fiber material and structure design to fundamental principle exploration in fiber lasers to practical applications of fiber laser systems.

We hope this feature issue provides a reference for scientists, engineers, and practitioners who are interested in the cutting-edge progress on fiber lasers and their applications, and may push forward new developments and discoveries in this exciting field.