Few-Layered Violet Phosphorene Nanostructures as Saturable Absorbers for Stable Soliton Mode-Locking Operations in an Ultrafast Fiber Laser

Two-dimensional (2D) layered nanosheets of violet phosphorene (VP) have great potential in optoelectronic applications owing to their unique electronic, mechanical, and optical properties. Herein, the nonlinear optical (NLO) properties of liquid-phase-exfoliated (LPE) VP nanosheets based on a side-polished D-shaped fiber (DSF) were experimentally investigated by a homemade dual-balance detection fiber system at the near-infrared band. A strong saturable absorption response was observed. The corresponding modulation depth and saturation intensity were determined as ∼1.57 and ∼68.1 MW/cm2, respectively. As an application, a VP-DSF saturable absorber mode-locked erbium-doped fiber laser was realized for the first time, generating ultrashort pulses with a pulse width of 799 fs. Moreover, the stable soliton molecule mode-locking pulses with a pulse width and time interval of 816 fs and 20.5 ps, respectively, were obtained by adjusting the polarization state in the same laser cavity. The experimental results demonstrated the potential use of VP-based nanomaterials in ultrafast photonics applications.