92,127 research outputs found

    Wavelength conversion for WDM communication systems using four-wavemixing in semiconductor optical amplifiers

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    Four-wave mixing (FWM) in semiconductor optical amplifiers is an attractive mechanism for wavelength conversion in wavelength-division multiplexed (WDM) systems since it provides modulation format and bit rate transparency over wide tuning ranges. A series of systems experiments evaluating several aspects of the performance of these devices at bit rates of 2.5 and 10 Gb/s are presented. Included are single-channel conversion over 18 nm of shift at 10 Gb/s, multichannel conversion, and cascaded conversions. In addition time resolved spectral analysis of wavelength conversion is presented

    Efficiency of broadband four-wave mixing wavelength conversion using semiconductor traveling-wave amplifiers

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    We present a theoretical analysis and experimental measurements of broadband optical wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers. In the theoretical analysis, we obtain an analytical expression for the conversion efficiency. In the experiments, both up and down-conversion efficiencies are measured as a function of wavelength shift for shifts up to 27 nm. The experimental data are well explained by the theoretical calculation. The observed higher conversion efficiency for wavelength down-conversion is believed to be caused by phase interferences that exist between various mechanisms contributing to the four-wave mixing process

    Polarization-dependent optical nonlinearities of multiquantum-well laser amplifiers studied by four-wave mixing

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    We present a detailed study of the polarization properties of four-wave mixing in multiquantum-well (MQW) semiconductor optical amplifiers (SOA's). In particular, the polarization selection rules relevant to all processes contributing to the generation of the four-wave mixing signal are rigorously derived and discussed. We then show the importance of these results in applications where four-wave mixing is used as a spectroscopic tool to study the optical nonlinearities of semiconductor gain media. For illustration, we demonstrate two novel applications of polarization-resolved four-wave mixing. The first is a new technique for measuring the recombination lifetime in SOA's, based on mixing of a pump wave with polarized amplified spontaneous emission noise. In the second, we use the same polarization selection rules to measure the interwell transport lifetime in alternating-strain MQW amplifiers. Finally, we also discuss the possibility of studying the dynamics of the optically induced phase coherence between spin-degenerate states

    Resonant tunnelling diode based high speed optoelectronic transmitters

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    Resonant tunneling diode (RTD) integration with photo detector (PD) from epi-layer design shows great potential for combining terahertz (THz) RTD electronic source with high speed optical modulation. With an optimized layer structure, the RTD-PD presented in the paper shows high stationary responsivity of 5 A/W at 1310 nm wavelength. High power microwave/mm-wave RTD-PD optoelectronic oscillators are proposed. The circuitry employs two RTD-PD devices in parallel. The oscillation frequencies range from 20-44 GHz with maximum attainable power about 1 mW at 34/37/44GHz.European Commission [645369

    Caging phenomena in reactions: Femtosecond observation of coherent, collisional confinement

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    We report striking observations of coherent caging of iodine, above the B state dissociation threshold, by single collisions with rare gas atoms at room-temperature. Despite the random nature of the solute–solvent interaction, the caged population retains coherence of the initially prepared unbound wave packet. We discuss some new concepts regarding dynamical coherent caging and the one-atom cage effect

    Spatial mode storage in a gradient echo memory

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    Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing. In this paper we investigate the spatial multimode properties of a lambda-GEM system. Using a high-speed triggered CCD, we demonstrate the storage of complex spatial modes and images. We also present an in-principle demonstration of spatial multiplexing by showing selective recall of spatial elements of a stored spin wave. Using our measurements, we consider the effect of diffusion within the atomic vapour and investigate its role in spatial decoherence. Our measurements allow us to quantify the spatial distortion due to both diffusion and inhomogeneous control field scattering and compare these to theoretical models.Comment: 11 pages, 9 figure

    Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber

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    Trapping and optically interfacing laser-cooled neutral atoms is an essential requirement for their use in advanced quantum technologies. Here we simultaneously realize both of these tasks with cesium atoms interacting with a multi-color evanescent field surrounding an optical nanofiber. The atoms are localized in a one-dimensional optical lattice about 200 nm above the nanofiber surface and can be efficiently interrogated with a resonant light field sent through the nanofiber. Our technique opens the route towards the direct integration of laser-cooled atomic ensembles within fiber networks, an important prerequisite for large scale quantum communication schemes. Moreover, it is ideally suited to the realization of hybrid quantum systems that combine atoms with, e.g., solid state quantum devices
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