Recent advances and challenges on dark solitons in fiber lasers

Dark solitons feature local dips on a modulationally stable continuous-wave background. Compared with bright solitons, the dark solitons in fiber lasers are more stable in noise circumstances and not much susceptible to loss. Thus, dark solitons have been widely applied in optics communication, optics sensing, and nonlinear optics fields. Although the mechanism of generation of dark solitons in fiber lasers has been numerically studied in the last almost five decades, the experimental observation of dark solitons from a fiber laser system just started since 2009, and it has attracted much attention. This review mainly describes the generation and propagation of nonlinear Schrodinger equation (NLSE) dark soliton in fiber lasers from both experimental and simulation perspectives, and then summarizes a detailed recent progress of the NLSE dark soliton, domain-wall dark soliton, and cubic-quintic nonlinear Schrödinger equation (CQNLSE) dark soliton. At the end of this review, the practical applications and perspectives of dark soliton fiber laser are also provided.