D.J. Feng

Direct synthesis of graphene on any nonmetallic substrate based on KrF laser ablation of ordered pyrolytic graphite

We present a method for few-layer graphene growth on nonmetallic substrates using excimer KrF laser ablation of ordered pyrolytic graphite. The graphene is scalable and its thickness is controllable. It can be deposited on virtually any nonmetallic substrates at a relative low temperature of 750??C. This laser-based method is highly efficient and the whole growing process takes less than 100?s. Raman spectroscopy confirms the formation of sp2-bonded carbon with a grain size of about 40?nm. The optical transmittance and conductivity of the graphene films are comparable with exfoliated or metal-catalyzed graphene. This work demonstrates a promising laser-based, transfer-free technique for synthesis of graphene.

Sapphire-based graphene saturable absorber for long-time working femtosecond lasers

We report a long-time working femtosecond laser using metal-free sapphire-based graphene as a saturable absorber (SA). The sapphire-based graphene yielded excellent nonlinear saturable absorption properties and was demonstrated to be suitable as an SA for an ultrafast solid-state laser. Stable mode-locked pulses of 325 fs were obtained at a central wavelength of 1032 nm with a repetition rate of 66.3 MHz. At pump power of 8.23 W the average output power was 1.78 W and the highest pulse energy reached 26.8 nJ with a peak power of 72.6 kW. Our work opens up a facile route for making reliable graphene SA in the mode-locking technique and also displays an exciting prospect in making low-cost and ultrafast lasers.

Facile fabrication of graphene-topological insulator Bi2Se3 hybrid Dirac materials via chemical vapor deposition in Se-rich conditions

Direct deposition of a uniform and high-quality Bi2Se3 thin film on a graphene film (layer controlled) is performed using a catalyst-free vapor deposition system in a Se-rich environment. The Se-rich environment is utilized to fill the Se vacancies and is beneficial to achieving the uniform chemical composition of the product. The layers of graphene can be controlled easily and precisely by the transfer times. Besides the graphene film, the morphology of the product is sensitive to the growth parameters (temperature of the substrate, growth time and gas flow). By controlling the growth parameters, we can also grow a crystal Bi2Se3 plate on the graphene/SiO2/Si substrate. Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction confirm the presence of uniform and high-quality Bi2Se3.

Direct growth of graphene on quartz substrate as saturable absorber for femtosecond solid-state laser

We present a novel method for the direct metal-free growth of graphene on quartz substrate. The direct-grown graphene yields excellent nonlinear saturable absorption properties and is demonstrated to be suitable as a saturable absorber (SA) for an ultrafast solid-state laser. Nearly Fourier-limited 367 fs was obtained at a central wavelength of 1048 nm with a repetition rate of 105.7 MHz. At a pump power of 7.95 W, the average output power was 1.93 W and the highest pulse energy reached 18.3 nJ, with a peak power of 49.8 kW. Our work opens an easy route for making a reliable graphene SA with a mode-locking technique and also displays an exciting prospect in making low-cost and ultrafast lasers.