Hexagonal boron nitride: a rising nonlinear optical material for dual-wavelength soliton generation

Abstract: The hexagonal boron nitride (h-BN) nanosheets are synthesized by the liquid-phase exfoliation method and transferred onto the microfiber by optical deposition method. The h-BN-deposited microfiber exhibits dual-function, that is, saturable absorption and high-nonlinearity. To check the laser performance by using the proposed h-BN device, it is inserted into an erbium-doped fiber laser (EDFL). In experiment, we demonstrate a tunable, switchable dual-wavelength soliton pulse by properly adjusting the pump power and the polarization state in the EDFL. The dual-wavelength soliton laser has a pump threshold of 50 mW at 976 nm, pulse energy of up to 3.4 nJ, peak power of about 2.62 kW, and pulse duration of about 1.3 ps. Additionally, we also demonstrate switchable operation of single-wavelength soliton pulse located at 1531.5 and 1557.5 nm, respectively. Our finding unambiguously implies that apart from its fantastic electric and thermal property, h-BN nanosheets may also possess attractive optoelectronic property for nonlinear photonics, such as mode-locker, Q-switcher, optical limiter and so on.