Low-dimensional carbon nanostructures such as carbon nanotubes (CNTs) and graphene
have been among the most interesting materials studied in recent decades. The inherently
fast response time, broadband linear absorption, and third-order nonlinearity of singlewalled
CNTs (SWCNTs) and graphene enable the application of these materials as ultrafast
broadband optical-switching devices, such as saturable absorbers (SAs). Owing to the
superior properties of carbon-nanostructure-based SAs, excellent mode-locking
performance has been demonstrated compared with the results achieved using conventional
semiconductor saturable absorber mirrors (SESAMs). Compared with SESAMs, carbon
nanostructures are more flexibly applied as SAs. To date, SWCNT and graphene are the most
frequently used SAs for ultrafast pulsed lasers. However, despite the substantial results
regarding carbon-nanostructure-based SAs, research on the broadband application and
engineering of SA parameters, e.g., the linear and nonlinear absorption properties, has not
yet been conducted.
In this thesis, the linear and nonlinear properties of SWCNT and graphene SAs are controlled
by various approaches. The delicate handling of carbon-nanostructure materials leads to the
uniform and low scattering losses of devices. By controlling the concentrations and
thicknesses of the SWCNT-SAs on transparent or reflective substrates, the linear absorption
of the devices can be modulated between less than 1% and over 30%. High-quality, largearea,
single-layer graphene is also fabricated, and flake-based graphene is suggested to
compensate for the limited gap of 2.3% intrinsic linear absorption per layer of the welldefined
single-layer graphene. The nonlinear optical characterization of the parameter controlled carbon-nanostructure-based SAs is performed in the broadband spectral region.
The fast recovery time of the devices is revealed for both the SWCNT and graphene SAs,
indicating that nonlinear optical properties can be engineered by modulating the linear
absorption of the devices using high-resolution nonlinear transmission measurements.
According to the parameter engineering technique, a novel type of SA for the compact-fiber
and bulk-laser system is suggested, including an all-in-one multifunctional SA mirror. The
varying thickness of the carbon-nanostructure SA on asymmetry structured platform,
polarization-dependent, evanescent field-coupled optical properties of the devices are
controllable. Material-injected fibers are also developed, for a robust and relatively long
nonlinear evanescent wave interaction in the fiber-laser system. Furthermore, sub-cm
waveguides are proposed for the device integration. These multifunctional, novel carbonnanostructure-
based SAs have been demonstrated for fiber and bulk solid-state laser modelocking
and ultra-compact waveguide laser Q-switched operations. Evanescent-waveinteraction-
type SWCNT and graphene-injected holey fibers exhibit a robust and relatively
high power operation compared with previous carbon-nanostructure-based SAs. The
application of an all-in-one SA on a single dielectric mirror is successfully demonstrated,
whereby the 30-cm-long laser cavity generates 150-fs pulses. The Q-switching operation of
the channel waveguide laser is also achieved using a modulation-depth-controlled SWCNTSA
mirror. Total length of 1-cm-long laser cavity with an SWCNT-coated output coupler
exhibits a stable Q-switched pulse generation; this is basic research for SWCNT and
graphene-based SA-mode-locked ultra-compact waveguide lasers.