Black phosphorus: broadband nonlinear optical absorption and application

Black phosphorus (BP), 2D layered material with layered dependent direct bandgap (0.3 eV (bulk), 2.0 eV (single layer)) that has gained renewed attention, has been demonstrated as an extremely appropriate optical material for broadband optical applications from infrared to mid-infrared wavebands. Herein, by coupling multi-layer BP films with microfiber, we fabricated a nonlinear optical device with long light-matter interaction distance and enhanced damage threshold. Through taking full advantage of its fine nonlinear optical absorption property, we obtained stable mode-locking (51 ps) and Q-switched mode-locking states in Yb-doped or Er-doped (403.7 fs) all-fiber lasers and the single-longitudinal-mode operation (53 kHz) in an Er-doped fiber laser with enhanced power tolerance, using the same nonlinear optical device. Our results showed that BP could be a favorable nonlinear optical material for developing BP-enabled wave-guiding photonic devices, and revealed new insight into BP for high optical power unexplored optical devices.