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.
Special Issue on Innovative Progress in Solid-State and Fiber Lasers for Industrial Applications