Search results for "Single"
showing 10 items of 4920 documents
Confined Pt-1(1+) Water Clusters in a MOF Catalyze the Low-Temperature Water-Gas Shift Reaction with both CO2 Oxygen Atoms Coming from Water
2018
[EN] The synthesis and reactivity of single metal atoms in a low-valence state bound to just water, rather than to organic ligands or surfaces, is a major experimental challenge. Herein, we show a gram-scale wet synthesis of Pt-1(1+) stabilized in a confined space by a crystallographically well-defined first water sphere, and with a second coordination sphere linked to a metal-organic framework (MOF) through electrostatic and H-bonding interactions. The role of the water cluster is not only isolating and stabilizing the Pt atoms, but also regulating the charge of the metal and the adsorption of reactants. This is shown for the low-temperature water-gas shift reaction (WGSR: CO + H2O CO2 + H…
Validation of a method for measuring the retinal thickness with Shack–Hartmann aberrometry in an artificial eye
2015
In Shack–Hartmann aberrometry, it is assumed that a wave front emerges from a single point focused on a retina. However, the retina is a multi-layered structure and reflections may occur from several layers. This may result in several overlapping spot patterns on the CCD due to different vergences of the outgoing wave fronts. The amount by which these spot patterns are displaced may contain information about the retinal thickness. In this study, we perform simulations of formation of double spots in a living eye and also apply this method to measure the thickness of an artificial retina with a simple structure. We also compare the results obtained with artificial eye and compare them to the…
Spatial and spectral nonlinear shaping of multimode waves
2016
We demonstrate a novel nonlinear dynamics of multimode fibers that reshapes their spectral and spatial beam profiles, based on spatiotemporal modulation instability. Sidebands ranging from the visible to the near-infrared are carried by one and the same spatial bell-shaped profile.
High repetition rates and high quality optical pulse train generator based on solitons over finite background
2013
This work proposes to fully exploit the nonlinear evolution undergone by a sinusoidal modulation with a finite background propagating along an optical fiber. For the original method to overcome this major drawback is to exploit the π phase shift that exists between the pulsed part and the background. By using a simple delay-line interferometer, it is possible to simultaneously double the repetition rate of the pulse train and to annihilate the deleterious background by imprinting a controlled π phase shift.
Limits of terrestrial optical fiber systems for ultra-high bit rate RZ data transmissions (from 160 Gbit/s to 1.28 Tbit/s)
2007
This article numerically investigates the fundamental limits of the terrestrial RZ data transmission systems based on SMF/DCF dispersion map for bit rates ranging from 160 Gbit/s to 1.28 Tbit/s. The system includes an erbium doped fiber amplifier and pre-and post-compensation stages. After filtering and detection, the system performance is characterized using the usual Q-factor.
Optical flip-flop memory and data packet switching operation based on polarization bistability in a telecommunication optical fiber
2013
We report the experimental observation of bistability and hysteresis phenomena of the polarization signal in a telecommunication optical fiber. This process occurs in a counterpropagating configuration in which the optical beam nonlinearly interacts with its own Bragg-reflected replica at the fiber output. The proof of principle of optical flip–flop memory and 10 Gbit/s routing operation is also reported based on this polarization bistability. Finally, we also provide a general physical understanding of this behavior on the basis of a geometrical analysis of an effective model of the dynamics. Good quantitative agreement between theory and experiment is obtained.
Akhmediev breathers as ultra-wideband pulses
2014
We analytically calculate and discuss the radio-frequency spectrum of the so called Akhmediev breathers (ABs), a class of nonlinear solutions of the nonlinear Schrodinger equation that governs the propagation in a single mode optical fiber. We propose a practical application of ABs to the field of ultra-wideband pulse generation. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:664–667, 2014
Temporal dynamics of incoherent waves in noninstantaneous response nonlinear Kerr media
2012
International audience; We consider the temporal evolution of an incoherent optical wave that propagates in a noninstantaneous response nonlinear medium, such as single mode optical fibers. In contrast with the expected Raman-like spectral redshift due to a delayed nonlinear response, we show that a highly noninstantaneous response leads to a genuine modulational instability of the incoherent optical wave. We derive a Vlasov-like kinetic equation that provides a detailed description of this process of incoherent modulational instability in the temporal domain.
Spectral dynamics of modulation instability described using Akhmediev breather theory
2011
International audience; The Akhmediev breather formalism of modulation instability is extended to describe the spectral dynamics of induced multiple sideband generation from a modulated continuous wave field. Exact theoretical results describing the frequency domain evolution are compared with experiments performed using single mode fiber around 1550 nm. The spectral theory is shown to reproduce the depletion dynamics of an injected modulated continuous wave pump and to describe the Fermi-Pasta Ulam recurrence and recovery towards the initial state. Realistic simulations including higher-order dispersion, loss and Raman scattering are used to identify that the primary physical factors that …
Dissipative soliton in a laser cavity: A novel concept in action
2006
International audience; The recent concept of a dissipative optical soliton sheds new light for understanding the stability of optical pulses that are generated in passively mode-locked lasers. Considering in these lasers the multiple pulsing regime of operation, the dissipative soliton concept is able to explain the great diversity of interaction behaviours that have been observed experimentally. Among the most spectacular behaviours are the formation of "soliton molecules" and "elastic-type" collisions. The dissipative soliton also explains the existence of complex limit cycles of pulsations within single pulse operation.