Sida Wu

Stable nanosecond pulse generation from a graphene-based passively Q -switched Yb-doped fiber laser

We demonstrate stable 70 ns pulse generation from a Yb-doped fiber laser passively Q-switched by a graphene-based saturable absorber mirror in a short linear cavity. The maximum output power was 12 mW and the highest single pulse energy was 46 nJ. The repetition rate of the fiber laser can be widely tuned from 140 to 257 kHz along with the increase of the pump power. To the best of our knowledge, this is the first report for passively Q-switched sub-100-ns pulse operation of a graphene-based saturable absorber in a Yb-doped fiber laser.

Graphene oxide mode-locked femtosecond erbium-doped fiber lasers

We demonstrated the femtosecond erbium-doped all-fiber lasers mode-locked with graphene oxide, which can be conveniently obtained from natural graphite by simple oxidation and ultra-sonication process. With proper dispersion management in an all-fiber ring cavity, the laser directly generated 200 fs pulses at a repetition rate of 22.9 MHz and the average output power was 5.8 mW. With the variation of net cavity dispersion, output pulses with pulse width of 0.2~3 ps were obtained at a repetition rate of 22.9~0.93 MHz. These results are comparable with those of graphene saturable absorbers and the superiority of easy fabrication and hydrophilic property of graphene oxide will facilitate its potential applications for ultrafast photonics.

Conductive graphene-based macroscopic membrane self-assembled at a liquid–air interface

Free-standing graphene-based macroscopic membranes, which are characterized by a layered structure and tunable conductivity, are prepared by a self-assembly process at a liquid–air interface. Since the preliminary results indicate that it is hard to construct macroscopic graphene membranes solely by low-temperature exfoliated graphene nanosheets (LGNs) at the liquid–air interface, graphene oxide nanosheets (GONs), as the stacking template and sticking component, are introduced into the assembly process of graphene layers to promote the formation of layer-by-layer stacking structure and help form a conductive macroscopic membrane. The conductivity of such a graphene-based membrane can be tuned by changing the GON fraction in the LGN/GON hybrid membrane.

Dissipative soliton generation from a graphene oxide mode-locked Er-doped fiber laser

We demonstrated dissipative soliton obtained from a graphene oxide mode-locked Er-doped fiber laser, which operated in normal dispersion cavity by employing the dispersion compensation fiber. The highly chirped pulses at the repetition rate of 19.5 MHz can be compressed from 11 ps to 542 fs by using single mode fiber. Numerical simulations were in good agreement with the experimental results. The hydrophilic graphene oxide with easier fabrication shows great potential to be a novel low-cost saturable absorber in reliable and compact mode-locked fiber laser system.

Graphene Emerges as a Versatile Template for Materials Preparation

Graphene and its derivatives are emerging as a class of novel but versatile templates for the controlled preparation and functionalization of materials. In this paper a conceptual review on graphene-based templates is given, highlighting their versatile roles in materials preparation. Graphene is capable of acting as a low-dimensional hard template, where its two-dimensional morphology directs the formation of novel nanostructures. Graphene oxide and other functionalized graphenes are amphiphilic and may be seen as soft templates for formatting the growth or inducing the controlled assembly of nanostructures. In addition, nanospaces in restacked graphene can be used for confining the growth of sheet-like nanostructures, and assemblies of interlinked graphenes can behave either as skeletons for the formation of composite materials or as sacrificial templates for novel materials with a controlled network structure. In summary, flexible graphene and its derivatives together with an increasing number of assembled structures show great potentials as templates for materials production. Many challenges remain, for example precise structural control of such novel templates and the removal of the non-functional remaining templates.

A graphene/poly(vinyl alcohol) hybrid membrane self-assembled at the liquid/air interface: enhanced mechanical performance and promising saturable absorber

A liquid–air self-assembly strategy is proposed to uniformly hybridize hydrophobic graphene with amphiphilic polymer, like PVA (poly(vinyl alcohol)), in a thin membrane, where the polymer imparts aqueous-dispersion and membrane-forming abilities to the encapsulated graphene. The microstructure, transmittance and wettability of the GNS/PVA hybrid membranes are finely tunable by changing the GNS fraction. Due to strong interaction between GNSs and PVA, the GNS-incorporated hybrid membrane formed at liquid–air interface shows improved thermal stability and highly enhanced mechanical performance as compared to GNS-free PVA membrane. Also, well-distributed GNS in the transparent polymer carrier make the hybrid membrane an ideal saturable absorber in ultrafast laser systems.

Mode-locked 2 μm thulium-doped fiber laser with graphene oxide saturable absorber

Few-layer graphene oxide depositing on broadband reflective mirror as a novel saturable absorber for mode-locking of a thulium-doped fiber laser at 2007 nm, which generated 0.56 nJ single pulse energy at 3.17 MHz repetition rate.

163 nJ graphene mode-locked Yb-doped fiber laser

High pulse-energy up to 163nJ is generated in a graphene mode-locked Yb-doped double-clad fiber laser with repetition-rate of 1.04-MHz. Graphene passive-Q-switched operation of ∼2.2μs pulse-width is also demonstrated with tunable repetition-rate from 6-kHz to 150-kHz.

Dissipative soliton resonance in an all-normal-dispersion graphene oxide mode-locked Yb-doped fiber laser

We observed dissipative soliton resonance in graphene oxide mode-locked Yb-doped fiber laser, which delivered square-shaped nanosecond pulses of 0.52ns~60.8ns and single pulse energy of 137.1nJ at 1064.9nm. The 3dB-bandwidth of Lorentz-shaped spectrum was 0.19nm.

Mode-locked and Q-switched Yb-doped fiber lasers with graphene saturable absorber

We report high pulse energy generation from an Yb-doped fiber laser mode-locked or passively Q-switched by a graphene saturable absorber. In the case of mode-locked operation, a ring cavity was used. The average output power is 170 mW and the repetition rate is 1.04 MHz, corresponding to single pulse energy of 163 nJ. To the best of our knowledge, this is the highest pulse energy reported for fiber lasers mode-locked with graphene saturable absorber. In the case of passively Q-switched operation, a linear cavity was used. The average output power is 12 mW and the repetition rate is 257 kHz, corresponding to single pulse energy of 46 nJ with pulse width of 70 ns. We believe we are among the first to report the stable passively Q-switched operation by graphene saturable absorber in a Yb-doped fiber laser as well. Graphene-based saturable absorber shows promising potential to replace SESAM as mode-locker or Q-switcher for pulsed lasers in the near future because of the good performance, easy fabrication, low cost and wide availability.