101 research outputs found

    Dispersion of coupled mode-gap cavities

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    The dispersion of a CROW made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the fact that the cavity mode profile itself is dispersive, i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. By taking into account the dispersive mode profile, we formulate a mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters.Comment: 4 pages, 4 figure


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    The problems of developing the risk assessment methods to estimate the level of safety of the vessel under the current conditions on a planned route before staring the pilotage as well as to make the decision on the beginning or suspension of pilotage in order to increase the level of navigational safety are discussed in the paper. Moreover, the application of the research results will reduce the affect of the human factor in decision-making in tasks related to the sea-going vessel’s operation. The developed method for the quantitative assessment of navigational risks will improve the safety of ship’s pilotage. It can also be applied in the decision-making support systems for the navigator in case of collision avoidance actions. The research results presented in this paper can be used to create automatic control systems

    MHD simulations of plasma dynamics in pinch discharges in capillary plasmas

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    Magnetohydrodynamic simulation results related to the capillary discharge dynamics are presented. The main physical process that should be taken into account is the ablation of the capillary wall material evaporated by the heat flux from the capillary plasma. The possible applications of the capillary discharges related to the physics of the X-ray lasers and the use of the capillary plasma to provide a guiding for ultrashort high-intensity laser pulses over a distance greater than the defocusing length are discussed

    The ALICE experiment at the CERN LHC

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    ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

    Dynamic tuning of photonic crystal nanocavities

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    Photonic crystal nanocavities play an important part in the future of nanophotonics. For many systems containing nanocavities it is necessary to be able to tune their essential parameters. In this thesis experimental investigation and control of properties of single and coupled photonic crystal nanocavities are presented. Experiments are supported by analytical and numerical calculations.\ud An apparatus was built to probe nanophotonic samples over a wide wavelength range of IR light. Local control of nanostructures was achieved thermally by local laser heating with several pump lasers, where one of them can be shaped by a spatial light modulator. External laser wavelength reference scheme is developed, which allows to perform measurements with high speed and resolution. \ud The local laser induced thermal tuning was found to greatly depend on the material of the nanostructure as well as on the ambient medium around the sample. We discovered that changing the ambient media from nitrogen to helium produces a change in the width of the temperature distribution by 30%, which easily allows an increase of the integration density of cavities on a nanophotonic chip.\ud We managed to control several coupled nanocavities independently in the presence of thermal crosstalk. As a result, we annulled the disorder and restored the intended state of the system. To show the full tunability we successfully tuned the coupling constant between nanocavities experimentally using two proposed methods. In one method we directly thermally perturb the membrane between two directly coupled nanocavities, while in another one we use ancillary cavity to control the coupling.\ud All post-pump time-dependent and permanent effects observed in experiments are summarized. While for some applications these changes are unwanted, for other ones they may be favorable, for example, permanent frequency shift may be applied to compensate disorder.\ud Finally, the value of the linear thermo-optical coefficient of GaInP for a freely expanding material is measured using an isolated nanocavity resonance. \ud The results described in this thesis extend boundaries of what can be achieved in nanophotonic circuits based on coupled nanocavities
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