High-Order Mode Mode-Locked Fiber Laser Based on Few-Mode Saturable Absorber

We presented two kinds of high-order mode (HOM) mode-locked fiber lasers based on few-mode (FM) saturable absorbers for direct HOM oscillation. One is a ring fiber laser based on a carbon nanotube (CNT) saturable absorber (SA), in which the combination of a long period fiber grating (LPFG) and a mode selective coupler (MSC) is used for the cycle of mode conversion between LP
₀₁
and LP
₁₁
modes. The other is a linear-cavity laser using a FM-based SESAM with the HOM oscillation, in which a MSC is used for mode conversion inside the cavity. The presented mode-locked fiber lasers can achieve the saturable absorption of the HOM and the cylindrical vector beams (CVBs). And we also compared the nonlinear saturation absorption characteristics of two SAs operating at LP
₀₁
and LP
₁₁
modes.