Intracavity Optical Deposition of Graphene Saturable Absorber for Low-Threshold Passive Mode-Locking of a Fiber Laser

A compact, intracavity optical deposition of graphene saturable absorber (SA) for low-threshold passively mode-locked fiber laser is proposed and demonstrated. The optical deposition is implemented in the laser cavity by using a slot collimator. Utilizing the fabricated graphene SA, the fiber laser achieves self-starting, passively mode-locked operation at a low threshold of 32 mW pump power, delivering a 13.1-MHz 2.36-ps pulse train.