Provost, L.
Parmigiani, F.
Petropoulos, P.
Richardson, D. J.
Mukasa, K.
Takahashi, M.
Hiroishi, J.
Tadakuma, M.
We demonstrate a four-channel extension to the Mamyshev regenerator and investigate its potential for the simultaneous processing of 4 x 10 Gb/s return-to-zero wavelength division-multiplexed channels. Mitigation of the interchannel nonlinearities is achieved through the rapid walkoff induced by both the large differential group delay of a specially developed polarization maintaining highly nonlinear fiber and a bidirectional architecture. Numerical and experimental results demonstrate the reduction of interchannel crosstalk as well as the potential of the scheme for 2R regeneration.
Parmigiani, F.
Jung, Y.
Gruner-Nielsen, L.
Geisler, T.
Petropoulos, P.
Richardson, D. J.
We experimentally demonstrate space division multiplexed data transmission using the LP01, LP11a and LP11b modes over a 1 km length of elliptical-core few mode fiber at 1550 nm using 10 Gb/s ON-OFF keying data per spatial channel. Space division multiplexed transmission without the use of any multiple input multiple output digital signal processing showed no power penalty relative to the single-mode or the back to back cases.
This Letter addresses a long-standing problem related to non-dynamical electron correlation effects. The origin of the large differential electronic correlation energy among the neutral 1S ground state, the lowest, 2P, ionic state and the first excited, 2S, ionic state of the Ne and Ar atoms is explained in terms of the near degeneracy of low-lying excited configurations. There is an anomalous correlation for the 2S state that is shown to be due to non-dynamical correlation involving a low-lying excited configuration. The conceptual framework used here is also appropriate to be used for other atomic and molecular systems. [All rights reserved Elsevier]
Parmigiani, F.
Rollandi, L.
Samoggia, G.
Depero, L.E.
A high resolution X-ray photoemission, XPS, study of PbMg1/3Nb2/3O3 is reported. The binding energy of the Pb core lines are consistent with a formal valence of 2+, while a valence of 5+ is found for Nb. In addition, on the basis of present data, the existence of different coordination sites for Pb, Nb and Mg is discarded. Finally, within the limit of the present experimental conditions, domains with non-homogeneous electrostatic charges, as proposed by some structural models, are not observed. Instead, the XPS results are consistent with a random distribution of Nb and Mg ions on the cationic site.
After the discovery of copper oxide based high temperature superconductors an extraordinary number of studies based on high energy spectroscopy measurements have been published. In this work we attempt to summarise, to the best of our knowledge, the more significant works concerning the Cu2p X-ray photoelectron core-lines. In particular, a critical study of the work done up to now shows that the most important question arises from a correct interpretation of the correlation mechanisms that determine the components and the weights of the copper configurations d 8, d 9 and d 10Llowbar in the XPS spectra
Petrovich, M. N.
Poletti, F.
Wooler, J. P.
Heidt, A. M.
Baddela, N. K.
Li, Z.
Gray, D. R.
Slavik, R.
Parmigiani, F.
Wheeler, N. V.
Hayes, J. R.
Numkam, E.
Gruner-Nielsen, L.
Palsdottir, B.
Phelan, R.
Kelly, B.
O'Carroll, John
Becker, M.
MacSuibhne, N.
Zhao, J.
Gunning, F. C. Garcia
Ellis, A. D.
Petropoulos, P.
Alam, S. U.
Richardson, D. J.
The first demonstration of a hollow core photonic bandgap fiber (HC-PBGF) suitable for high-rate data transmission in the 2 mu m waveband is presented. The fiber has a record low loss for this wavelength region (4.5 dB/km at 1980 nm) and a > 150 nm wide surface-mode-free transmission window at the center of the bandgap. Detailed analysis of the optical modes and their propagation along the fiber, carried out using a time-of-flight technique in conjunction with spatially and spectrally resolved (S-2) imaging, provides clear evidence that the HC-PBGF can be operated as quasi-single mode even though it supports up to four mode groups. Through the use of a custom built Thulium doped fiber amplifier with gain bandwidth closely matched to the fiber's low loss window, error-free 8 Gbit/s transmission in an optically amplified data channel at 2008 nm over 290 m of 19 cell HC-PBGF is reported. (C) 2013 Optical Society of America
Magnano, E.
Carleschi, E.
Nicolaou, A.
Pardini, T.
Zangrando, M.
Parmigiani, F.
MnSi is a ferromagnetic compound with a Curie temperature of 29 K. Recent theoretical studies predict that 2 ML of MnSi epitaxially grown on Si show a ferromagnetic metallic ground state with spin polarization. of about 50%. This would allow the development of spintronic devices based on the injection of spin-polarized current from a ferromagnetic metal into a semiconductor. In this context the possibility of growing in situ MnSi on the Si(111) surface has been explored. Thermal reaction, crystalline structure and electronic properties of the grown films have been studied in situ by photoemission spectroscopy (PES), X-ray absorption spectroscopy (XAS), and low energy electron diffraction (LEED). Depositing a thin film of Mn on Si(111) the formation of ordered islands (with dimensions dependent on the amount of deposited Mn) is driven by annealing at selected temperatures, as already observed. Our preliminary studies show that by simultaneously depositing Mn and Si in 1:1 stoichiometry on Si(111) a large improvement in the homogeneity of the MnSi films is achieved. (c) 2006 Elsevier B.V. All rights reserved.
Provost, L.
Parmigiani, F.
Finot, C.
Mukasa, K.
Petropoulos, P.
Richardson, D. J.
We report a 2R optical regenerator based on the Self-Phase Modulation and offset filtering technique in a bi-directional architecture for the simultaneous processing of two optical channels at 10 Gb/s within a single highly nonlinear fiber. Whereas excellent mitigation of the inter-channel nonlinear crosstalk is experimentally demonstrated, we identify Rayleigh backscattering as the major source of crosstalk and show how it is related to the regenerator parameters and operational settings. Finally, we demonstrate that this crosstalk does not introduce any significant additional penalties as compared to single channel operation. (c) 2008 Optical Society of America.
Aronne, A.
Fanelli, E.
Pernice, P.
Malvestuto, M.
Bergese, P.
Bontempi, E.
Colombi, P.
Depero, L. E.
Bignardi, L.
Giannetti, C.
Ferrini, G.
Parmigiani, F.
This communication presents and discusses an experimental proof of the correlation among local structure and second harmonic generation (SHG) in bulk nanostructured potassium niobiosilicate (KNS) glasses. In particular. SHG shows a maximum in correspondence of the early stages of nanostructuring, that are characterized by the segregation within the amorphous matrix of nanosized inhomogeneities. EXAFS experiments indicate that these inhomogeneities are determined by the maximum size reached by the niobium second coordination shell combined with the sudden inclusion of potassium atoms in it. Such rearrangement at the local level determines the maximum fluctuation of the bulk glass refractive index and in turn its maximum SHG activity. (C) 2010 Elsevier B.V. All rights reserved.
An impurity-cluster configuration-interaction model that treats charge transfer and exchange correlations on the same footing is applied to interpret the 3s core-level X-ray photoelectron spectra of NiO, CoO, K 2NiF 4 and K 2CoF 4. The interplay between charge transfer and exchange correlations in determining the final state satellite structures is clarified and an estimate of the exchange integrals between the 3s hole and the 3d electrons is given. The results are consistent with the electronegativity scale, as regards charge transfer energy, and with the trend suggested by the Van Vleck rule, as concerns the exchange integrals
Zangrando, M.
Cudin, I.
Fava, C.
Gerusina, S.
Gobessi, R.
Godnig, R.
Rumiz, L.
Svetina, C.
Parmigiani, F.
Cocco, D.
The Italian Free Electron Laser (FEL) facility FERMI@Elettra has started to produce photon radiation at the end of 2010. The photon beam is presently delivered by the first undulator chain (FEL1) that is supposed to produce photons in the 100-20 nm wavelength range. A second undulator chain (FEL2) will be commissioned at the end of 2011, and it will produce radiation in the 20-4nm range. The Photon Analysis Delivery and Reduction System (PADReS) was designed to collect the radiation coming from both the undulator chains (FEL1 and FEL2), to characterize and control it, and to redirect it towards the following beamlines. The first parameters that are checked are the pulse-resolved intensity and beam position. For each of these parameters two dedicated monitors are installed along PADReS on each FEL line. In this way it possible to determine the intensity reduction that is realized by the gas reduction system, which is capable of cutting the intensity by up to four orders of magnitude. The energy distribution of each single pulse is characterized by an online spectrometer installed in the experimental hall. Taking advantage of a variable line-spacing grating it can direct the almost-full beam to the beamlines, while it uses a small fraction of the beam itself to determine the spectral distribution of each pulse delivered by the FEL. The first light of FERMI@Elettra, delivered to the PADReS section in late 2010, is used for the first commissioning runs and some preliminary experiments whose results are reported and discussed in detail.