Graphene Actively Mode-Locked Lasers

Actively mode-locked lasers offer varying degrees of flexibility for a wider range of applications than their passively modulated counterparts, due to their capability for electrically controlled ultrahigh repetition rate operation. Graphene based electrooptic modulators with unique advantages of broad operation bandwidth and ultrafast speed are suitable for light modulation in various optoelectronic applications. Here, an actively mode-locked laser with a graphene based electrooptic modulator is reported for the first time. The active mode-locking technique combined together with the intracavity nonlinear pulse shortening effect allows the generation of transform-limited 1.44 ps pulses with pulse energy of 844 pJ. The electrically controlled repetition rate of generated pulses, a key performance advantage of active mode-locking, is also demonstrated. These results provide a practical and effective approach for actively mode-locked lasers with broad operation bandwidth and compact footprint, which contributes a new way for applications of two-dimensional (2D) layered materials in ultrafast lasers.