We propose and demonstrate the cascaded multi-wavelength mode-locked erbium-doped fiber laser (EDFL) based on ultra-long-period gratings (ULPGs) for the first time, to the best of our knowledge. Study found that the ULPG can be used as both a mode-locker for pulse shaping and a comb filter for multi-wavelength generation simultaneously. Using the dual-function of ULPG, three-, four-, five-, six-, and seven-wavelength mode-locked pulses are obtained in EDFL, seven of which are the largest number of wavelengths up to now. For the four-wavelength soliton pulses, their pulse width is about 7.8 ps. The maximum average output power and slope efficiency of these pulses are 8.4 mW and 2.03%, respectively. Besides the conventional pulses, hybrid soliton pulses composed of a four-wavelength pulse and single soliton are also observed. Finally, the effect of cavity dispersion on the multi-wavelength mode-locked pulses is also discussed. Our findings indicate that apart from common sensing and filtering, the ULPG may also possess attractive nonlinear pulse-shaping property for ultrafast photonics application.

Ultrafast lasers play an important role in a variety of applications ranging from optical communications to medical diagnostics and industrial materials processing. Graphene and other two-dimensional (2D) noncarbon materials, including topological insulators (TIs), transition metal dichalcogenides (TMDCs), phosphorene, bismuthene, and antimonene, have witnessed a very fast development of both fundamental and practical aspects in ultrafast photonics since 2009. Their unique nonlinear optical properties enable them to be used as excellent saturable absorbers (SAs) that have fast responses and broadband operation, and can be easily integrated into lasers. Here, we catalog and review recent progress in the exploitation of these 2D noncarbon materials in this emerging field. The fabrication techniques, nonlinear optical properties, and device integration strategies of 2D noncarbon materials are first introduced with a comprehensive view. Then, various mode-locked/Q-switched lasers (e.g., fiber, solid-state, disk, and waveguide lasers) based on 2D noncarbon materials are reviewed. In addition, versatile soliton pulses generated from the mode-locked fiber lasers based on 2D noncarbon materials are also summarized. Finally, future challenges and perspectives of 2D materials-based lasers are addressed.