Multi-wavelength mode-locked fiber laser based on bend-induced-birefringence comb filter effect

Multi-wavelength fiber lasers have emerged as a promising source for the application in wavelength division multiplexing communication and terahertz wave generation due to their high efficiency and robustness. This paper introduces a section of bent long single-mode fiber (SMF) into the semiconductor saturable absorption mirror and nonlinear polarization rotation hybrid mode-locked Er-doped fiber laser to enhance intra-cavity birefringence to realize wavelength interval tunable dual-wavelength mode-locking and stationary triwavelength mode-locking. Dual-wavelength mode-locking has variable wavelength intervals within 11.502 nm-29.541 nm. Tri-wavelength mode-locking can be switched pair-to-pair by adjusting the intra-cavity polarization state. The bent-SMF-induced optimized birefringence comb filter effect is responsible for multiwavelength mode-locking. Such compact multi-wavelength mode-locked fiber lasers with flexible outputs can meet many applications.