Fig. 1. (a) Schematic of graphene/WS2 heterostructure on sapphire substrate. (b) Raman spectrum of the WS2 sample. (c) Raman spectra of monolayer graphene. (d) PL spectrum measured from graphene/WS2 heterostructure, WS2, and graphene excited by 532 nm solid-state laser at room temperature. (e) Typical open-aperture Z-scan curves with normalized transmission as a function of sample position Z.

Fig. 2. Schematic of the experimental setup for Q-switched waveguide laser. Inset is an optical photograph of the graphene/WS2 heterostructure on sapphire substrate.

Fig. 3. Efficient Q-switched Nd:YVO4 waveguide laser emission. (a) Emission spectrum of Q-switched waveguide laser modulated by graphene/WS2 heterostructure. Insert is the pulse trains of Q-switched pulsed laser. (b) Output power versus the launched power. Inset is the evolution of measured near-field modal profile of the graphene/WS2-based pulsed laser as the increase of launched power.

Fig. 4. Comparison of the parameters of pulsed laser Q-switched by SAs of graphene/WS heterostructure, WS2, and graphene. (a) Repetition rate and pulse duration as a function of launched power. (b) Pulse energy and peak power as a function of launched power.