Transition-metal dichalcogenides heterostructure saturable absorbers for ultrafast photonics

In this Letter, high-quality WS₂ film and MoS₂ film were vertically stacked on the tip of a single-mode fiber in turns to form heterostructure (WS₂-MoS₂-WS₂)-based saturable absorbers with all-fiber integrated features. Their nonlinear saturable absorption properties were remarkable, such as a large modulation depth (∼16.99%) and a small saturable intensity (6.23  MW·cm^-2). Stable pulses at 1.55 μm with duration as short as 296 fs and average power as high as 25 mW were obtained in an erbium-doped fiber laser system. The results demonstrate that the proposed heterostructures own remarkable nonlinear optical properties and offer a platform for adjusting nonlinear optical properties by stacking different transition-metal dichalcogenides or modifying the thickness of each layer, paving the way for engineering functional ultrafast photonics devices with desirable properties.