Layer-dependent nonlinear optical properties of 2D SiTe2 for ultrafast laser applications

In this paper, we have systematically investigated the principle of layer-dependent band structure and nonlinear optical properties, as well as the resulting differences in optical modulation for ultrafast laser performance. Ultrasonic liquid-phase exfoliation is employed to synthesize single-layer SiTe 2 nanosheets with a direct-bandgap structure and multilayer SiTe 2 nanosheets with an indirect-bandgap structure. The nonlinear absorption characteristics, revealed by [Formula: see text]-scan and [Formula: see text]-scan measurements, show that single-layer SiTe 2 exhibits a nonlinear absorption coefficient of −6.2[Formula: see text]cm/GW and a modulation depth of 7.6%, while multilayer SiTe 2 demonstrates values of −1.7[Formula: see text]cm/GW, 5.1%, respectively. Using single-layer and multilayer SiTe 2 nanosheets as saturable absorbers, continuous wave mode-locking Yb:GdScO 3 lasers are achieved with pulse widths of 149[Formula: see text]fs and 280[Formula: see text]fs, respectively, at a repetition rate of 63[Formula: see text]MHz. The maximum average output power reaches 381[Formula: see text]mW with a signal-to-noise ratio greater than 65[Formula: see text]dB. As far as we know, this is the first report on the use of SiTe 2 , whose band structure is layer-number-dependent, for ultrafast laser generation. These findings provide significant insights for optimizing the performance of ultrafast lasers.