We investigated nonlinear optical characteristics of Tungsten disulfide (WS2) films and experimentally demonstrated their high potential for application as nonlinear saturable absorbers in passively mode-locked fiber lasers. Side polished fiber (SPF) was fabricated and WS2 film was overlaid to provide an efficient evanescent field interaction. The WS2 film was prepared using two methods: liquid phase exfoliation to form few-layer nano-sheets, and chemical vapor deposition (CVD) to grow uniform multilayer WS2 on a SiO2 substrate. Two SPF saturable absorbers were prepared by either spin coating WS2 solution or lifting off the multilayer CVD WS2 on SPF. An all-fiber ring cavity was built and the WS2 film overlaid on SPF was employed as a mode locker along with Er-doped fiber as a gain medium. Using the spin-coated WS2 SPF, stable soliton-like pulses were generated with a spectral width of 5.6 nm and 467 fs pulse duration. The fiber laser cavity containing CVD WS2 SPF generated a transform-limited soliton pulse train with a spectral width of 8.23 nm and a pulse duration of 332 fs. Our study confirmed a high potential of WS2 film as a novel 2-D nonlinear optical material for laser applications.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics