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.