Passively Q-Switched and Mode-Locked Laser Generation in 3μm Fluoride Fibers Based on Tellurium/Graphene Heterojunction Saturable Absorber

Faced with the problem that the low modulation depth and saturation intensity of mid-infrared saturable absorbers (SAs) make it difficult to achieve higher pulse energy passively [Formula: see text]-switched, this paper successfully produced [Formula: see text]-switched and mode-locked mid-infrared 3[Formula: see text][Formula: see text]m lasers in fluoride fiber lasers using tellurium/graphene (Te/G) heterojunctions as SAs. Stable [Formula: see text]-switched pulses are achieved at low pump power, with a maximum repetition rate of 106.3[Formula: see text]kHz and a shortest pulse width of 2.36[Formula: see text][Formula: see text]s. The corresponding maximum output power reaches 63.1[Formula: see text]mW, with a slope efficiency of 25.5%, and the corresponding pulse energy is 0.594[Formula: see text][Formula: see text]J. Moreover, as the pump power increases, the laser enters the continuous-wave mode-locked state. The maximum average output power of the [Formula: see text]m mode-locked laser reaches 149.3[Formula: see text]mW at 1.19[Formula: see text]W, with a slope efficiency of 10.3%. This represents the first successful demonstration of passively [Formula: see text]-switched and mode-locked laser in fluoride lasers operating in the mid-infrared [Formula: see text]m region using Te/G heterojunction SA. The experimental results demonstrate that heterojunctions are an effective method to improve nonlinearity, which is a promising approach to achieve high-efficiency pulsed laser.