Graphene Q-switched Er,Yb:GdAl₃(BO₃)₄ laser at 1550  nm

A single-layer graphene saturable absorber is employed for passive Q-switching of an Er, Yb:GdAl₃(BO₃)₄ (Er,Yb:GdAB) compact laser, representing the first Er-doped oxoborate laser Q-switched by graphene. This laser is based on a c-cut 1.8 at. % Er³⁺, 15 at. % Yb³⁺:GdAB crystal diode-pumped at 0.976 μm. It generates a maximum average output power of 360 mW at 1.55 μm with a slope efficiency of 23% (with respect to the incident power). Stable ∼1  μJ/130  ns pulses are achieved at a repetition rate of 400 kHz. This result represents, to the best of our knowledge, the shortest pulse duration ever achieved in bulk Er lasers Q-switched by 2D materials. Graphene is a promising material for generating nanosecond pulses at high repetition rates (MHz range) in Er-doped oxoborate lasers emitting in the eye-safe range at 1.5-1.7 μm.