Graphene passively Q-switched two-micron fiber lasers

We demonstrate a passively Q-switched thulium fiber laser, using a graphene-based saturable absorber. The laser is based on an all-fiber ring cavity and produces ∼2.3 μs pulses at 1884nm, with a maximum pulse energy of 70 nJ. © 2012 OSA.

Ultrafast non-thermal electron dynamics in single layer graphene

We study the ultrafast dynamics of non-thermal electron relaxation in graphene upon impulsive excitation. The 10-fs resolution two color pump-probe allows us to unveil the non-equilibrium electron gas decay at early times. © 2012 OSA.

Mode-locking by nanotubes of a Raman laser based on a highly doped GeO 2 fiber

A mode-locked Raman laser, using 25 m of a GeO2 doped fiber as the gain medium, is reported employing carbon nanotubes. The oscillator generates 850 ps chirped pulses, which are externally compressed to 185 ps. © 2012 OSA.

Pulsewidth switchable, wavelength tuneable ultrafast fiber laser mode-locked by carbon nanotubes

Employing a nanotube-based saturable absorber, we demonstrate a continuously tunable (1533-1563nm) ultrafast fiber laser, with output pulsewidth switchable between picosecond (1.2 ps) and femtosecond (610 fs) regimes. © 2012 IEEE.

Dual-wavelength, carbon nanotube mode-locked fiber laser

We demonstrate a dual-wavelength, carbon nanotube mode-locked Er fiber laser. The laser outputs two wavelengths at 1549nm and 1562nm, and each wavelength corresponds to pulse duration of ∼1.3ps and repetition rate of ∼11.27MHz. © 2012 IEEE.

2 μm solid-state laser mode-locked by single-layer graphene

We report a 2 μm ultrafast solid-state Tm: Lu2O3 laser, mode-locked by single-layer graphene, generating transform-limited ∼ 410 fs pulses, with a spectral width ∼ 11.1 nm at 2067 nm. The maximum average output power is 270 mW, at a pulse repetition frequency of 110 MHz. This is a convenient high-power transform-limited ultrafast laser at 2 μm for various applications, such as laser surgery and material processing. © 2013 American Institute of Physics.

Production and processing of graphene and 2d crystals

Graphene is at the center of an ever growing research effort due to its unique properties, interesting for both fundamental science and applications. A key requirement for applications is the development of industrial-scale, reliable, inexpensive production processes. Here we review the state of the art of graphene preparation, production, placement and handling. Graphene is just the first of a new class of two dimensional materials, derived from layered bulk crystals. Most of the approaches used for graphene can be extended to these crystals, accelerating their journey towards applications. © 2012 Elsevier Ltd.

Measurement of the elastic constants of nanometric films

Carbon coatings of thickness down to 2 nanometers are needed to increase the storage density in magnetic hard disks and reach the 100 Gbit/in2 target. Methods to measure the properties of these ultrathin hard films still have to be developed. We show that combining Surface Brillouin Scattering (SBS) andX-ray reflectivity measurements the elastic constants of such films are accessible. Tetrahedral amorphous carbofilms of thickness down to about 2 nm were deposited on Si by an S bend filtered cathodic vacuum arc, achieving a continuous coverage on large areas free of macroparticles. Film thickness and mass density are measured by X-ray reflectivity: densities above 3 g/cm3 are found, indicating a significant sp3 content. The dispersion relations of surface acoustic waves are measured by SBS. We show that for thicknesses above ∼4 nm these waves can be described by a continuum elastic model based on a single homogeneous equivalent film. The elastic constants can then be obtained by fitting the dispersion relations, computed for given film properties, to the measured dispersion relations. For thicknesses of 3 nm or less qualitative differences among films are well measurable, but quantitative results are less reliable. We have thus shown that we can grow and characterise nanometer size tetrahedral amorphous carbon film, which maintain their high density and peculiar mechanical properties down to around 4 nm thickness, satisfying the requirements set for the hard disk coating material.

On the photoluminescence of a-C:H films

a-C:H films deposited from methane and helium mixture in a capacitively coupled rf plasma were found to show photoluminescence (PL) with peak intensities at energies far above the Taue gap of these films. Apart from the PL the films were investigated with respect to their IR and UV/VIS absorption properties as well as their Raman spectra were examined. The ultraviolet (UV) and blue luminescence from hard a-C:H thin films are explained by incorporation of polycyclic hydrocarbons from gas-phase reactions in the methane helium plasma into the film.

Brillouin scattering of cluster-assembled carbon films

The low frequency vibrational spectrum of cluster beam deposited carbon films was studied by Brillouin light scattering. In thin films the values of both bulk modulus and shear modulus has been estimated from the shifts of surface phonon peaks. The values found indicate a mainly sp2 coordinated random network with low density. In thick films a bulk longitudinal phonon peak was detected in a spectral range compatible with the value of the index of refraction and of the elastic constants of thin films. High surface roughness, combined with a rather strong bulk central peak, prevented the observation of surface phonon features. © 1998 Elsevier Science Ltd. All rights reserved.

Electroluminescence in Single Layer MoS2

We detect electroluminescence in single layer molybdenum disulphide (MoS2) field-effect transistors built on transparent glass substrates. By comparing absorption, photoluminescence, and electroluminescence of the same MoS2 layer, we find that they all involve the same excited state at 1.8eV. The electroluminescence has pronounced threshold behavior and is localized at the contacts. The results show that single layer MoS2, a direct band gap semiconductor, is promising for novel optoelectronic devices, such as 2-dimensional light detectors and emitters.

Nanowire and graphene architectures for room temperature THz detection

Antenna-coupled field effect transistors have been developed as plasma-wave THz detectors in both InAs nanowire and graphene channel material. Room temperature operation has been achieved up to frequencies of 1.5 THz, with noise equivalent powers as low as a few 10-11 W/Hz1/2, and high-speed response. © 2012 IEEE.

Multiwall nanotubes, multilayers, and hybrid nanostructures: new frontiers for technology and Raman spectroscopy.

Technological progress is determined, to a great extent, by developments in material science. Breakthroughs can happen when a new type of material or new combinations of known materials with different dimensionality and functionality are created. Multilayered structures, being planar or concentric, are now emerging as major players at the forefront of research. Raman spectroscopy is a well-established characterization technique for carbon nanomaterials and is being developed for layered materials. In this issue of ACS Nano, Hirschmann et al. investigate triple-wall carbon nanotubes via resonant Raman spectroscopy, showing how a wealth of information can be derived about these complex structures. The next challenge is to tackle hybrid heterostructures, consisting of different planar or concentric materials, arranged "on demand" to achieve targeted properties.