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Now showing items 33 - 48 of 100

  • On the role of athermal electrons in non-linear photoemission from Ag(100) RID G-2395-2010

    Giannetti, C.   Ferrini, G.   Pagliara, S.   Galimberti, G.   Banfi, F.   Pedersoli, E.   Parmigiani, F.  

    The non-linear photoelectron spectra obtained by short laser pulses from a Ag(100) surface show a high-energy electron emission due to an athermal electron distribution created by the laser pulse. By comparing the photoemission at normal and non-normal emission geometry it is possible to evidence the independence of the hot electron photoemission on the parallel momentum and on different final-state configurations. A photoemission correlation measurement evidences that non-photoelectric effects, as tunneling or thermally assisted photoemission, do not contribute to the electron yield. Various theoretical models are discussed on the basis of the present data.
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  • Optical interconnection of core and metro networks RID C-9253-2011 RID D-5528-2009 RID C-7539-2009

    Ellis, A. D.   Cotter, D.   Ibrahim, S.   Weerasuriya, R.   Chow, C. W.   Leuthold, J.   Freude, W.   Sygletos, S.   Vorreau, P.   Bonk, R.   Hillerkuss, D.   Tomkos, I.   Tzanakaki, A.   Kouloumentas, C.   Richardson, D. J.   Petropoulos, P.   Parmigiani, F.   Zarris, G.   Simeonidou, D.  

    A network concept is introduced that exploits transparent optical grooming of traffic between an access network and a metro core ring network. This network is enabled by an optical router that allows bufferless aggregation of metro network traffic into higher-capacity data streams for core network transmission. A key functionality of the router is WDM to time-division multiplexing (TDM) transmultiplexing. (C) 2008 Optical Society of America
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  • All-optical pulse reshaping and retiming systems incorporating pulse shaping fiber Bragg grating

    Parmigiani, F.   Petropoulos, P.   Ibsen, M.   Richardson, D.J.  

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  • An Efficient Wavelength Converter Exploiting a Grating-Based Saw-Tooth Pulse Shaper RID C-7539-2009

    Parmigiani, F.   Ibsen, M.   Ng, T. T.   Provost, L.   Petropoulos, P.   Richardson, D. J.  

    We experimentally demonstrate the generation of picosecond triangular optical pulses using a superstructured fiber Bragg grating and show experimentally that use of this pulse shape can provide a three-fold improvement in conversion efficiency relative to the use of Gaussian pulses with similar pulsewidths when used in a wavelength conversion scheme based on self-phase modulation and subsequent offset filtering.
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  • Investigation of Four-Wavelength Regenerator Using Polarization- and Direction-Multiplexing RID C-7539-2009

    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.
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  • Elliptical Core Few Mode Fibers for Multiple-Input Multiple Output-Free Space Division Multiplexing Transmission

    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.
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  • Elliptical Core Few Mode Fibers for Multiple-Input Multiple Output-Free Space Division Multiplexing Transmission

    Parmigiani, F.   Jung, Y.   Gruner-Nielsen, L.   Geisler, T.   Petropoulos, P.   Richardson, D. J.  

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  • Anomalous electron correlation due to near degeneracy effects: low-lying ionic states of Ne and Ar

    Bagus, P.S.   Broer, R.   Parmigiani, F.  

    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]
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  • ssingle crystals

    Parmigiani, F.   Sangaletti, L.   Goldoni, A.   del Pennino, U.   Kim, C.   Shen, Z.-X.   Revcolevschi, A.   Dhal`enne, G.  

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  • X-ray photoelectron study of the relaxor lead magnesium niobate

    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.
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  • OTDM to WDM format conversion based on quadratic cascading in a periodically poled lithium niobate waveguide

    Kwang Jo Lee   Sheng Liu   Parmigiani, F.   Ibsen, M.   Petropoulos, P.   Gallo, K.   Richardson, D.J.  

    We propose and demonstrate error-free conversion of a 40 Gbit/s optical time division multiplexed signal to 4 times 10 Gbit/s wavelength division multiplexed channels based on cascaded second harmonic and difference frequency generation in a periodically poled lithium niobate waveguide. The technique relies on the generation of spectrally (and temporally) flat linearly chirped pulses which are then optically switched with short data pulses in the nonlinear waveguide. Error-free operation was obtained for all channels with a power penalty below 2 dB.
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  • Multi-electron excitations in the optical and X-ray photoelectron spectra of NiO

    Parmigiani, F.   Samoggia, G.   Sangaletti, L.  

    A study of multi-electron excitations in the O 1s X-ray photoemission (XP) region of NiO single crystal is reported. The observed spectral lines are discussed and assigned to surface and bulk plasmon losses on the basis of a Kramers-Kronig analysis of the 0-30 eV range reflectivity data.
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  • Optimisation of amplitude limiters for phase preservation based on the exact solution to degenerate four-wave mixing

    Bottrill, K. R. H.   Hesketh, G.   Parmigiani, F.   Richardson, D. J.   Petropoulos, P.  

    Adopting an exact solution to four-wave mixing (FWM), wherein harmonic evolution is described by the sum of two Bessel functions, we identify two causes of amplitude to phase noise conversion which impair FWM saturation based amplitude regenerators: self-phase modulation (SPM) and Bessel-order mixing (BOM). By increasing the pump to signal power ratio, we may arbitrarily reduce their impact, realising a phase preserving amplitude regenerator. We demonstrate the technique by applying it to the regeneration of a 10 GBaud QPSK signal, achieving a high level of amplitude squeezing with minimal amplitude to phase noise conversion. (C) 2016 Optical Society of America
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  • Investigation of simultaneous 2R, regeneration of two 40-Gb/s channels in a single optical fiber RID C-7539-2009

    Provost, L.   Parmigiani, F.   Petropoulos, P.   Richardson, D. J.  

    We experimentally investigate the simultaneous all-optical signal processing of two 40-Gb/s wavelength-division-multiplexing optical streams spaced by similar to 5 nm using self-phase modulation and offset filtering in a single highly nonlinear fiber to achieve a 2R optical regeneration. Using a bidirectional configuration, we demonstrate efficient mitigation of the interchannel crosstalk. We experimentally observe no degradation of the regenerator performance arising from the presence of the second channel as compared to the single-channel case.
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  • Angle resolved photoemission of NiO(001)

    Shen, Z.X.   List, R.S.   Dessau, D.S.   Arko, A.J.   Barttlet, R.   Jepsen, O.   Wells, B.O.   Parmigiani, F.  

    The authors report off-normal angle-resolved photoemission data from NiO(001), which is complementary to the earlier normal-emission result. On the one hand, the energy position of the bands along this direction and the dispersion of the lowest oxygen band agree with the band calculation very well. On the other hand, the existence of the valence band satellite and the absence of the energy band in the gap region do not agree with the band calculation. For the first time, interesting movement of the Ni d7 satellite has been observed as a function of the emission angle and the photon energy, which is most likely a result of the satellite dispersion
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  • single crystals

    Parmigiani, F.   Shen, Z. X.   Mitzi, D. B.   Lindau, I.   Spicer, W. E.   Kapitulnik, A.  

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