Showing papers by "Y. R. Shen published in 2015"
TL;DR: In this article, the authors report the observation of plasmons that exhibit quantized velocities in carbon nanotubes and show that the velocity can be quantized in the presence of carbon atoms.
Abstract: The authors report the observation of plasmons that exhibit quantized velocities in carbon nanotubes.
124 citations
TL;DR: Sum-frequency vibrational spectroscopy was employed to probe polymer contaminants on chemical vapor deposition (CVD) graphene and to study alkane and polyethylene (PE) adsorption on graphite, finding that the contaminants must be long-chain alkane or PE-like molecules.
Abstract: Sum-frequency vibrational spectroscopy was employed to probe polymer contaminants on chemical vapor deposition (CVD) graphene and to study alkane and polyethylene (PE) adsorption on graphite. In comparing the spectra from the two surfaces, it was found that the contaminants on CVD graphene must be long-chain alkane or PE-like molecules. PE adsorption from solution on the honeycomb surface results in a self-assembled ordered monolayer with the C–C skeleton plane perpendicular to the surface and an adsorption free energy of ∼42 kJ/mol for PE(H(CH2CH2)nH) with n ≈ 60. Such large adsorption energy is responsible for the easy contamination of CVD graphene by impurity in the polymer during standard transfer processes. Contamination can be minimized with the use of purified polymers free of PE-like impurities.
38 citations
TL;DR: Meng et al. as discussed by the authors demonstrated saturable absorption behavior in these nanofibers with a saturation threshold down to 0.25 pJ pulse−1 (peak power ∼ 1.3 W) using 1064-nm-wavelength nanosecond pulses as switching light.
Abstract: Graphene-doped polymer nanofibers are fabricated by taper drawing of solvated polyvinyl alcohol doped with liquid-phase exfoliated graphene flakes. Nanofibers drawn this way typically have diameters measured in hundreds of nanometers and lengths in tens of millimeters; they show excellent uniformity and surface smoothness for optical waveguiding. Owing to their tightly confined waveguiding behavior, light–matter interaction in these subwavelength-diameter nanofibers is significantly enhanced. Using approximately 1350-nm-wavelength femto-second pulses, we demonstrate saturable absorption behavior in these nanofibers with a saturation threshold down to 0.25 pJ pulse−1 (peak power ∼1.3 W). Additionally, using 1064-nm-wavelength nanosecond pulses as switching light, we show all-optical modulation of a 1550-nm-wavelength signal light guided along a single nanofiber with a switching peak power of ∼3.2 W. Graphene-doped polymer nanofibers have been used to perform low-threshold nonlinear switching and modulation of light. Chao Meng and co-workers fabricated the nanofibers by drawing a solvated polymer containing liquid-phase exfoliated graphene flakes. The resulting nanofibers typically had diameters of several hundred nanometers and lengths of tens of millimetres. The nanofibers’ tight confinement of light on the subwavelength scale enhances light–matter interactions and allows nonlinear effects such as saturable absorption to occur at low optical powers. Using 1064-nm-wavelength, nanosecond control pulses as a switch, a 1550-nm signal was all-optically modulated in the nanofiber with a switching peak power of about 3.2 W. The researchers say that the nanofibers feature excellent surface smoothness and uniformity and are promising for use in nanophotonic circuits and devices.
37 citations