Demonstration of passively Q-switched and mode-locked operations through dispersion control in Er-doped fiber lasers with a cylindrite-based saturable absorber

Abstract

Two-dimensional (2D) materials have been extensively investigated in the fields of electronics, biology, and chemistry. Especially in the field of optoelectronics, profiting from 2D layered materials-based photonic devices, such as optical switchers, optical modulators, and optical polarizers, new research areas of ultrashort pulse lasers have been opened up. Cylindrite is a kind of sulfosalt mineral with highly anisotropic optical responses. Two isotropic layers, a SnS2-like layer and a PbS-like layer, are stacked together to form a natural van der Waals heterostructure. Thin cylindrite flakes can be obtained through both mechanical exfoliation (ME) and liquid-phase exfoliation (LPE) methods. In this work, cylindrite nanosheets are prepared successfully by the LPE method. Nonlinear optical absorption properties are studied firstly in advance of exploring the potential of cylindrite as optical modulators. Dispersion management is realized by increasing the length of single-mode fiber. And with the intracavity net dispersion (IND) changing from −0.24 ps2 to −4.47 ps2, both Q-switched and mode-locked operations could be observed in a cylindrite-based Er-doped fiber laser (EDFL) in turn. Q-switched pulses outputs are obtained when the IND are about −0.24 ps2 and -0.68 ps2. The maximum average output power is 1.71 mW. The obtainable maximum single pulse energy is 53.89 nJ. Mode-locked operations are demonstrated when the IND are about −0.91 ps2, -2.01 ps2, -3.44 ps2, and -4.47 ps2. Besides, a double-ended pumped mode-locked EDFL with a signal-to-noise ratio of about 51 dB can also be obtained. This work reveals the nice nonlinear optical properties of the cylindrite-based saturable absorber and indicates that the cylindrite-based optical modulator holds tremendous potential and feasibility in the field of ultrashort pulse fiber lasers.