All-fiber hybrid NPR and NL-MMI mode-locked laser with high-order mode generation

This paper reports an all-fiber mode-locked erbium-doped laser-integrated higher-order mode (HOM) conversion that generates HOMs using a homemade mode-selective coupler and achieves stable mode-locking by combining the nonlinear polarization rotation and nonlinear multimode interference. The laser shows a slope efficiency of 7.9% and achieves stable single-pulse generation at a low turn-on threshold of 69.5 mW. By precisely controlling the pump power and cavity polarization state, this work achieves dynamically reconfigurable high harmonic mode locking up to 12th-order, soliton rain, noise-like pulse. This laser structure will be suitable for photonic systems, particularly in precision laser micromachining and fiber-optic communication networks.