Comb-based WDM transmission at 10 Tbit/s using a DC-driven quantum-dash mode-locked laser diode

Chip-scale frequency comb generators have the potential to become key building blocks of compact wavelength-division multiplexing (WDM) transceivers in future metropolitan or campus-area networks. Among the various comb generator concepts, quantum-dash (QD) mode-locked laser diodes (MLLD) stand out as a particularly promising option, combining small footprint with simple operation by a DC current and offering flat broadband comb spectra. However, the data transmission performance achieved with QD-MLLD was so far limited by strong phase noise of the individual comb tones, restricting experiments to rather simple modulation formats such as quadrature phase shift keying (QPSK) or requiring hard-ware-based compensation schemes. Here we demonstrate that these limitations can be over-come by digital symbol-wise phase tracking algorithms, avoiding any hardware-based phase-noise compensation. We demonstrate 16QAM dual-polarization WDM transmission on 38 channels at an aggregate net data rate of 10.68 Tbit/s over 75 km of standard single-mode fiber. To the best of our knowledge, this corresponds to the highest data rate achieved through a DC-driven chip-scale comb generator without any hardware-based phase-noise reduction schemes

Hybrid Organic-Inorganic Coordination Complexes as Tunable Optical Response Materials.

Novel lead and bismuth dipyrido complexes have been synthesized and characterized by single-crystal X-ray diffraction, which shows their structures to be directed by highly oriented π-stacking of planar fully conjugated organic ligands. Optical band gaps are influenced by the identity of both the organic and inorganic component. Density functional theory calculations show optical excitation leads to exciton separation between inorganic and organic components. Using UV-vis, photoluminescence, and X-ray photoemission spectroscopies, we have determined the materials' frontier energy levels and show their suitability for photovoltaic device fabrication by use of electron- and hole-transport materials such as TiO2 and spiro-OMeTAD respectively. Such organic/inorganic hybrid materials promise greater electronic tunability than the inflexible methylammonium lead iodide structure through variation of both the metal and organic components

Understanding the electronic structure of Y2Ti2O5S2 for green hydrogen production: a hybrid- DFT and GW study

Combined hybDFT and GW study reveals surface properties and optoelectronic behaviour of Y2Ti2O5S2 for green hydrogen production

A Theoretical Exploration of Emerging Solar Absorber Materials

Renewable energy sources are the only sustainable solutions that can address the increasing worldwide demand for energy without significantly furthering anthropogenic climate change and damage to our environment. Photovoltaics are able to harness the massive amount of solar radiation onto the earth each day through direct conversion to electricity, however have historically been expensive to produce and deploy on a large scale. In this thesis, we examine some of the challenges facing current photovoltaic technologies and how recently-developed materials, such as the inorganic-organic lead halide perovskites, have inspired the search for materials that may be used to provide highly-efficient, yet also cheap, mass-producible and flexible solar cells. Through ab initio density functional theory, we examine three families of compounds and, through the calculation of their electronic, optical and defect properties, are able to assess their suitability and potential as absorbers within photovoltaic devices. The caesium silver bismuth halides are lead-free analogues of the lead halide perovskites, however our calculations demonstrate that they are limited in comparison to their lead counterparts due to a mismatch in orbital angular momentum in their electronic structure, weakening their absorption. The silver copper sulfides have also shown recent promise as solar absorber materials, although we show that consideration of the optical properties is essential in successfully predicting the potential of such emergent materials. Finally, our survey of the lead bismuth sulfides predicts a promising compound for solar absorption, including the cell architecture that would be necessary to produce high device efficiencies. Through this study, we can accurately calculate properties of these materials but also hope to provide guidance in the future search for new photovoltaic technologies at the atomic scale

A "Idade do Ferro-B" e a cultura castreja do Noroeste da Península Ibérica. Novas luzes acerca de um antigo problema.

76 (1-2) Jan.-Jun. 1966, p. 117-146

A influência do povo "Beaker" no primeiro período da Idade do Bronze na Europa Ocidental.

60 (3-4) Jul.-Dez. 1950, p. 350-375

A Idade do Bronze Atlântico no Sudoeste da Europa.

61 (3-4) Jul.-Dez. 1951, p. 323-377

Nonlinear impairment compensation using expectation maximization for dispersion managed and unmanaged PDM 16-QAM transmission

In this paper, we show numerically and experimentally that expectation maximization (EM) algorithm is a powerful tool in combating system impairments such as fibre nonlinearities, inphase and quadrature (I/Q) modulator imperfections and laser linewidth. The EM algorithm is an iterative algorithm that can be used to compensate for the impairments which have an imprint on a signal constellation, i.e. rotation and distortion of the constellation points. The EM is especially effective for combating non-linear phase noise (NLPN). It is because NLPN severely distorts the signal constellation and this can be tracked by the EM. The gain in the nonlinear system tolerance for the system under consideration is shown to be dependent on the transmission scenario. We show experimentally that for a dispersion managed polarization multiplexed 16-QAM system at 14 Gbaud a gain in the nonlinear system tolerance of up to 3 dB can be obtained. For, a dispersion unmanaged system this gain reduces to 0.5 dB

Understanding the Photocatalytic Activity of La₅Ti₂AgS₅O₇ and La₅Ti₂CuS₅O₇ for Green Hydrogen Production:Computational Insights

[Image: see text] Green production of hydrogen is possible with photocatalytic water splitting, where hydrogen is produced while water is reduced by using energy derived from light. In this study, density functional theory (DFT) is employed to gain insights into the photocatalytic performance of La(5)Ti(2)AgS(5)O(7) and La(5)Ti(2)CuS(5)O(7)—two emerging candidate materials for water splitting. The electronic structure of both bulk materials was calculated by using hybrid DFT, which indicated the band gaps and charge carrier effective masses are suitable for photocatalytic water splitting. Notably, the unique one-dimensional octahedral TiO(x)S(6–x) and tetragonal MS(4) channels formed provide a structural separation for photoexcited charge carriers which should inhibit charge recombination. Band alignments of surfaces that appear on the Wulff constructions of 12 nonpolar symmetric surface slabs were calculated by using hybrid DFT for each of the materials. All surfaces of La(5)Ti(2)AgS(5)O(7) have band edge positions suitable for hydrogen evolution; however, the small overpotentials on the largest facets likely decrease the photocatalytic activity. In La(5)Ti(2)CuS(5)O(7), 72% of the surface area can support oxygen evolution thermodynamically and kinetically. Based on their similar electronic structures, La(5)Ti(2)AgS(5)O(7) and La(5)Ti(2)CuS(5)O(7) could be effectively employed in Z-scheme photocatalytic water splitting