Infrared Saturable Absorption Properties of Tungstenene Nanosheets for Passively Q-Switched 1.9 μm Solid-State Laser

Tungsten is a transition-metal element that belongs to the VIB group and is one of the 90 naturally occurring elements. In this paper, we prepared tungstenene nanosheets by liquid-phase exfoliation and first demonstrated their nonlinear saturable absorption properties at a 2 μm waveband. The high-performance 1.9 μm passively Q-switched lasers were realized with tungstenene as a saturable absorber, which exhibited the advantages of high repetition rate, short pulse width, and high peak power. Under a pulse pumping mode with a repetition rate of 10 Hz, the single-pulse energy and peak power reached 87.96 μJ and 605.81 W, respectively, which are superior to all two-dimensional (2D) saturable absorbers reported before. These results have shown that tungstenene can be used as a high-quality optical modulator for a 2 μm laser.