Tungsten diselenide for all-fiber lasers with the chemical vapor deposition method.

Two-dimensional materials have become the focus of research for their photoelectric properties, and are employed as saturable absorption materials. Currently, the challenge is how to further improve the modulation depth of saturable absorbers (SAs) based on two-dimensional materials. In this paper, three kinds of WSe2 films with different thicknesses are prepared using the chemical vapor deposition method. The nonlinear optical responses of the WSe2 films including the nonlinear saturable absorption and nonlinear refractive index are characterized by the double-balanced detection method and Z-scan experiments. Different modulation depths are successfully obtained by controlling the thickness of the WSe2 films. We further incorporate them into an all-fiber laser to generate mode-locked pulses. The mode-locked fiber lasers with a pulse duration of 185 fs, 205.7 fs and 230.3 fs are demonstrated when the thickness of the WSe2 films is measured to be 1.5 nm, 5.7 nm and 11 nm, respectively. This work provides new prospects for WSe2 in ultrafast photonic device applications.