RESUMO
Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics1 and as a means of revealing2,3 or even inducing4,5 broken symmetries. Emerging methods for light-based current control5-16 offer particularly promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometre spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science. Here we introduce vectorial optoelectronic metasurfaces in which ultrafast light pulses induce local directional charge flows around symmetry-broken plasmonic nanostructures, with tunable responses and arbitrary patterning down to subdiffractive nanometre scales. Local symmetries and vectorial currents are revealed by polarization-dependent and wavelength-sensitive electrical readout and terahertz (THz) emission, whereas spatially tailored global currents are demonstrated in the direct generation of elusive broadband THz vector beams17. We show that, in graphene, a detailed interplay between electrodynamic, thermodynamic and hydrodynamic degrees of freedom gives rise to rapidly evolving nanoscale driving forces and charge flows under the extremely spatially and temporally localized excitation. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, THz spectroscopies, nanomagnetism and ultrafast information processing.
RESUMO
Mode-locked erbium-doped fiber lasers are ideal comb generators for optical frequency metrology. We compare two fiber frequency combs by measuring an optical frequency independently with both combs and comparing their results. The two frequency measurements agree within 6x10-16. This is to our knowledge the first direct comparison between two fiber based frequency combs.
RESUMO
A highly efficient and widely tunable narrow linewidth ytterbiumdoped double-clad fiber laser with a linearly polarized output power of 10 W is demonstrated. The laser wavelength was tunable over a range of 24 THz from 1032 nm to 1124 nm by using a diffraction-grating pair in Littrow-Littman configuration in a unidirectional ring-cavity. The laser linewidth was smaller than 2.5 GHz for all power levels and all laser wavelengths. Additionally, an operating mode without any measurable amplified spontaneous emission with a linearly polarized output power of up to 3 W was realized.
RESUMO
A diode-pumped mode-locked double clad Yb3+-fiber ring laser with up to 118 nm bandwidth, a repetition rate of 7.6 MHz and a maximum output power of 2.8 W is presented. The broad bandwidth is achieved by suppressing the long wavelength components in the dispersive grating line of the resonator.
