Preparation of 2D WS 2 /MoS 2 Heterostructure via S-vacancy Doping and its Application in Ultrafast Laser Modulation

Abstract

Saturable absorbers (SAs) are core components in fiber lasers. In recent years, transition metal dichalcogenides have been widely used as SAs in fiber lasers due to their excellent saturable absorption performance. Here, two-dimensional (2D) WS 2 /MoS 2 heterojunctions with S vacancy defects are fabricated by regulating S vacancies. Based on this, a novel WS 2 /MoS 2based SA is prepared. Experimental results show that SAs achieve stable mode-locking phenomena in erbium-doped fiber lasers (EDFLs) and ytterbium-doped fiber lasers (YDFLs). In EDFLs, the WS 2 /MoS 2 -based SA (5:4) generates 682 fs pulses. In YDFLs, the WS 2 /MoS 2 -based SA (1:1) produces 748 fs pulses. Additionally, the WS 2 /MoS 2 -based SA (5:3) ratio generates dualwavelength pulses in the 1 μm and 1.5 μm bands in fiber lasers. Meanwhile, based on the first-principles calculation, the dielectric constants of WS 2 /MoS 2 heterojunction with S vacancies are summarized, achieving a clever combination of microscopic atomic structure and macroscopic optical properties. The presence of vacancy defects and heterostructures optimizes the optical modulation performance of the WS 2 /MoS 2 -based SA. This study not only provides a universal method for preparing WS 2 /MoS 2 -based SA but also theoretically explains the optimization of optical modulation by the vacancy defects and heterostructures, offering a reference for the development of two-dimensional SAs.