WS(2) mode-locked ultrafast fiber laser

Graphene-like two dimensional materials, such as WS(2) and MoS(2), are highly anisotropic layered compounds that have attracted growing interest from basic research to practical applications. Similar with MoS(2), few-layer WS(2) has remarkable physical properties. Here, we demonstrate for the first time that WS(2) nanosheets exhibit ultrafast nonlinear saturable absorption property and high optical damage threshold. Soliton mode-locking operations are achieved separately in an erbium-doped fiber laser using two types of WS(2)-based saturable absorbers, one of which is fabricated by depositing WS(2) nanosheets on a D-shaped fiber, while the other is synthesized by mixing WS(2) solution with polyvinyl alcohol, and then evaporating them on a substrate. At the maximum pump power of 600 mW, two saturable absorbers can work stably at mode-locking state without damage, indicating that few-layer WS(2) is a promising high-power flexible saturable absorber for ultrafast optics. Numerous applications may benefit from the ultrafast nonlinear features of WS(2) nanosheets, such as high-power pulsed laser, materials processing, and frequency comb spectroscopy.