All-Fiber Saturable Absorbers for Ultrafast Fiber Lasers

摘要： The past decade has witnessed tremendous achievements of ultrafast ?ber laser technologies due to rapid developments of saturable absorbers (SAs) based on, in particular, nanomaterials such as 0D quantum dot, 1D carbon nanotubes, 2D layered materials, and 3D nanostructures. However, most of those nanomaterials-based SAs are inevitably absence of the high damage threshold and all-?ber integration, therefore challenging their applications on highly integrated and high-energy pulse generations. Recently, the real all-?ber SAs based on the nonlinear multimodal interference (NLMMI) technique using multimode ?bers are demonstrated to overcome the above limitations. In this review, a detailed summary of the recent advances in NLMMI-based all-?ber SAs is provided, including the fundamental theory, implementation scenarios, and ultrafast ?ber lasers of the all-?ber SAs, covering wide wavelength range of 1, 1.55, and 2 μm. In addition to the state-of-the-art overview, optical rogue waves in the all-?ber SA-based ultrafast ?ber laser are extensively analyzed, which reveals the laser physics behind the dynamics from low-energy to high-energy pulses and directs the design of high-energy ultrafast ?ber lasers. The conclusions and perspectives of the all-?ber SAs are also discussed at the end.