This paper emphasizes on overviewing the developing progress of the state-of-the-art carbon nanomaterial-based saturable absorbers for passively mode-locked fiber lasers, including carbon nanotube (CNT), graphene, graphite and other carbon nanomaterials. With reviewing the performances of these proposed candidates, the characteristic parameters required for initiating and stabilizing the passive mode-locked fiber lasers are summarized for comparison and discussion. At first, the basic characteristics such as saturation intensity and self-amplitude-modulation (SAM) coefficients of the CNT material with different-wall types are discussed in detail. In comparison, the single-wall CNT possesses optical nonlinearity better than double-wall CNT, whereas the doublewall CNT exhibits wavelength tenability and the multi-wall CNT fails to initiate mode-locking. Subsequently, different graphene saturable absorbers with slightly changing their optical properties made by various fabrication technologies are introduced to take over the role of typical CNT saturable absorber. The detailed analyses on graphene saturable absorber for developing various types of passively mode-locked fiber lasers are overviewed. At last, other new-aspect graphite and carbon nanomaterials related saturable absorbers have emerged because they reveal similar optical nonlinearity with graphene but exhibit cost-effectiveness and easy-production. When changing saturable absorber from graphene to other carbon nanomaterials, the modulation depth is decreased but the saturation intensity is concurrently enlarged because of the disordered structure with increased interlayer spacing and reduced graphene content. At the current stage, selecting carbon nanomaterials with high nonlinear absorbance and low saturated intensity for large SAM coefficient is the golden rule for passively mode-locked the fiber lasers in future academic and industrial applications.

本文着重概述用于无源锁模光纤激光器的基于碳纳米材料的可饱和吸收剂的最新技术进展，包括碳纳米管（CNT），石墨烯，石墨和其他碳纳米材料。通过审查这些候选的性能，总结了用于启动和稳定无源锁模光纤激光器所需的特征参数，以进行比较和讨论。首先，详细讨论了不同壁类型的CNT材料的基本特性，例如饱和强度和自振幅调制（SAM）系数。相比之下，单壁CNT的光学非线性要好于双壁CNT，而双壁CNT表现出波长持久性，而多壁CNT无法启动锁模。随后，引入了由各种制造技术制造的光学性能略有变化的不同石墨烯可饱和吸收剂，以取代典型的CNT可饱和吸收剂的作用。概述了用于开发各种类型的被动锁模光纤激光器的石墨烯可饱和吸收剂的详细分析。最后，出现了其他与石墨和碳纳米材料有关的可饱和吸收剂，因为它们显示出与石墨烯相似的光学非线性，但具有成本效益和易于生产的特点。当将可饱和吸收剂从石墨烯改为其他碳纳米材料时，由于层间间距增加和石墨烯含量降低的无序结构，调制深度减小，但饱和强度同时增大。在当前阶段，对于大的SAM系数，选择具有高非线性吸收和低饱和强度的碳纳米材料是在未来的学术和工业应用中被动锁模光纤激光器的黄金法则。