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Thomas Erneux - One of the best experts on this subject based on the ideXlab platform.
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all optical controlled switching between time periodic Square Waves in diode lasers with delayed feedback
Optics Letters, 2014Co-Authors: Gaetan Friart, Jan Danckaert, Guy Verschaffelt, Thomas ErneuxAbstract:We investigate the Square-wave (SW) self-modulation output of an edge-emitting diode laser subject to polarization rotated optical feedback in detail, both experimentally and theoretically. Our experimental results show that the 2τ-periodic SW, where τ is the delay of the feedback, coexists with other SW oscillations of shorter periods. We have found that these new SWs are specific harmonics of the fundamental one and their periods are P(n)≃2τ/(1+2n), where n is an integer. Numerical simulations and analytical studies of laser rate equations confirm the multistability of SW solutions. By adding a weak conventional optical feedback, we show that the switching between the different periodic SWs can be easily controlled. The delay of this feedback control is the key parameter determining the harmonic that is stabilized. Numerical simulations corroborate the effectiveness of our experimental control scheme.
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Slow-fast dynamics of a time-delayed electro-optic oscillator
Philosophical Transactions of the Royal Society A: Mathematical Physical and Engineering Sciences, 2013Co-Authors: Lionel Weicker, Thomas Erneux, Ottilde D'huys, Jan Danckaert, Maxime Jacquot, Yanne K. Chembo, Laurent LargerAbstract:Square-wave oscillations exhibiting different plateau lengths have been observed experimentally by investigating an electro-optic oscillator. In a previous study, we analysed the model delay differential equations and determined an asymptotic approximation of the two plateaus. In this paper, we concentrate on the fast transition layers between plateaus and show how they contribute to the total period. We also investigate the bifurcation diagram of all possible stable solutions. We show that the Square Waves emerge from the first Hopf bifurcation of the basic steady state and that they may coexist with stable low-frequency periodic oscillations for the same value of the control parameter.
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Strongly asymmetric Square Waves in a time-delayed system
Physical Review E, 2012Co-Authors: Lionel Weicker, Thomas Erneux, Ottilde D'huys, Jan Danckaert, Maxime Jacquot, Yanne K. Chembo, Laurent LargerAbstract:Time-delayed systems are known to exhibit symmetric Square Waves oscillating with a period close to twice the delay. Here, we show that strongly asymmetric Square Waves of a period close to one delay are possible. The plateau lengths can be tuned by changing a control parameter. The problem is investigated experimentally and numerically using a simple bandpass optoelectronic delay oscillator modeled by nonlinear delay integrodifferential equations. An asymptotic approximation of the Square-wave periodic solution valid in the large delay limit allows an analytical description of its main properties (extrema and Square pulse durations). A detailed numerical study of the bifurcation diagram indicates that the asymmetric Square Waves emerge from a Hopf bifurcation.
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asymmetric Square Waves in mutually coupled semiconductor lasers with orthogonal optical injection
Physical Review E, 2010Co-Authors: David W. Sukow, Thomas Erneux, Athanasios Gavrielides, Benjamin Mooneyham, Karen Lee, Jake Mckay, Josiah W DavisAbstract:Two edge-emitting lasers mutually coupled through orthogonal optical injection exhibit Square-wave oscillations in their polarization modes. The TE and TM modes within each individual laser are always in antiphase, but the TE mode of one laser leads the TM of the other by the one-way time of flight between lasers. The duty cycle of the Square Waves is tunable with pump current and coupling strength, while the total period remains close to the roundtrip time. Numerical simulations give similar results and reveal the role of noise in stabilizing the oscillations.
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Asymmetric Square-Waves in mutually coupled semiconductor lasers
Semiconductor Lasers and Laser Dynamics III, 2008Co-Authors: David W. Sukow, Thomas Erneux, Athanasios Gavrielides, Josiah W Davis, Makhosazana Z.makhosazana Dube, Saneliso Mabuza, Russell TrimmerAbstract:Two edge-emitting lasers coupled through polarization-rotated optical injection exhibit Square-wave oscillations provided the roundtrip time from laser to laser and back is sufficiently large. If the mutual coupling between the lasers is relatively weak, the two plateaus of the Square-Waves exhibit different durations even though the total period remains close to the roundtrip time. This asymmetry progressively disappears as the feedback strength is increased. The experimental observations are confirmed by numerical simulations. The simulations also reveal that the Square-wave regimes appear through a series of complex bifurcations and that a sufficiently large roundtrip time is needed.
Athanasios Gavrielides - One of the best experts on this subject based on the ideXlab platform.
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Polarization Square-wave switching in orthogonally delay-coupled semiconductor lasers
2011Co-Authors: Cristina Masoller, Marc Sciamanna, Athanasios GavrielidesAbstract:Simulations based on semiconductor laser rate equations, extended to take into account time-delayed orthogonal optical coupling, show transient Square-Waves before a steady-state is reached. In the steady-state the lasers emit either orthogonal linearly polarized modes, or mix-modes where both polarizations coexist. The influence of various model parameters on the duration of the transient dynamics is investigated.
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simple and complex Square Waves in an edge emitting diode laser with polarization rotated optical feedback
Physical Review E, 2010Co-Authors: Athanasios Gavrielides, David W. Sukow, Guinevere Burner, Taylor Mclachlan, J Miller, Jake AmonetteAbstract:Numerical and experimental results are presented for an edge-emitting diode laser with delayed optical feedback, where the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. We examine the bifurcation structure and dynamics that give rise to a class of periodic, polarization-modulated solutions, the simplest of which is a Square wave solution with a period related to but longer than twice the external cavity roundtrip time. Such solutions typically emerge when the feedback is strong and the differential losses in the normally unsupported polarization mode are small. We also observe more complex waveforms that maintain the same periodicity.
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asymmetric Square Waves in mutually coupled semiconductor lasers with orthogonal optical injection
Physical Review E, 2010Co-Authors: David W. Sukow, Thomas Erneux, Athanasios Gavrielides, Benjamin Mooneyham, Karen Lee, Jake Mckay, Josiah W DavisAbstract:Two edge-emitting lasers mutually coupled through orthogonal optical injection exhibit Square-wave oscillations in their polarization modes. The TE and TM modes within each individual laser are always in antiphase, but the TE mode of one laser leads the TM of the other by the one-way time of flight between lasers. The duty cycle of the Square Waves is tunable with pump current and coupling strength, while the total period remains close to the roundtrip time. Numerical simulations give similar results and reveal the role of noise in stabilizing the oscillations.
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Asymmetric Square-Waves in mutually coupled semiconductor lasers
Semiconductor Lasers and Laser Dynamics III, 2008Co-Authors: David W. Sukow, Thomas Erneux, Athanasios Gavrielides, Josiah W Davis, Makhosazana Z.makhosazana Dube, Saneliso Mabuza, Russell TrimmerAbstract:Two edge-emitting lasers coupled through polarization-rotated optical injection exhibit Square-wave oscillations provided the roundtrip time from laser to laser and back is sufficiently large. If the mutual coupling between the lasers is relatively weak, the two plateaus of the Square-Waves exhibit different durations even though the total period remains close to the roundtrip time. This asymmetry progressively disappears as the feedback strength is increased. The experimental observations are confirmed by numerical simulations. The simulations also reveal that the Square-wave regimes appear through a series of complex bifurcations and that a sufficiently large roundtrip time is needed.
Eduard Montgomery Meira Costa - One of the best experts on this subject based on the ideXlab platform.
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resonance on coils excited by Square Waves explaining tesla transformer
IEEE Transactions on Magnetics, 2010Co-Authors: Eduard Montgomery Meira CostaAbstract:In this paper, effects of induced electromotive force (EMF) on coils excited by Square Waves are shown, as well as how these influence resonance phenomena. The work was based on experimental results, using planar coils and inner ring coils. A priori, the resonance is presented as effects of parasitic capacitances on coils, which through inclusion of external capacitances, is established that the phenomenon of high voltage on output is the sum of responses of the induced EMF added with response to step voltage on rise and fall of the Square wave. Consequently, the found results explicate the phenomenon of high energy (or high voltage) in the output of Tesla transformer.
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planar transformers excited by Square Waves
Progress in Electromagnetics Research-pier, 2010Co-Authors: Eduard Montgomery Meira CostaAbstract:This paper presents an analysis of found results in experiments developed with transformers built with planar coils, when they are excited by Square Waves, in comparison with transformers built with planar coils inner ring coils. The transformer was built joining two planar coils one over the other. In this kind of transformer, similar responses as analysis of transformers built with planar coil inner ring coil are found, as well the results of resonance. Because the low self-inductances and parasitic capacitances obtained in these configurations, although the coils resistance is low, which generates low exponential drops on responses. The resonance is found in higher frequencies, but satisfying conditions of sum of responses in resonance.
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resonance on transformers excited by Square Waves and explanation of the high voltage on tesla transformer
Progress in Electromagnetics Research B, 2009Co-Authors: Eduard Montgomery Meira CostaAbstract:This paper presents an analysis about resonance on coupled systems when excited by Square Waves, generated through experiments using planar and ring coils. Because of the phenomenon described by its transfer function, a sum of responses appear when the Square wave frequency increases, which causes a resonance response with high voltage, in several cases, greater than common turn ratio of the transformer. With parallel capacitances inserted on output, the resonance frequency reduction and change of gain is observed. Due to this efiect, explanation of how output of Tesla transformer presents high voltage which is shown and strategies to reach the maximal value on output are proposed.
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resonance between planar coils vs ring coils excited by Square Waves
Progress in Electromagnetics Research B, 2009Co-Authors: Eduard Montgomery Meira CostaAbstract:This paper presents a basic analysis about experiment results using planar coils inner ring coils, deflning a transformer, when this system is excited by Square wave voltage. In this study phenomena of response to step voltage due to parasitic capacitances is analyzed, and a sum of responses when the input Square wave frequency increases is given too. These phenomena are uncommon in literature, which can be applied to several areas of researches in electrical engineering, pulse transformers and power electronics.
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responses in trasnformers built with planar coils inner ring coils excited by Square Waves
Progress in Electromagnetics Research B, 2009Co-Authors: Eduard Montgomery Meira CostaAbstract:This paper presents an analysis about the results of experiments using planar coils inner ring coils to determine a transformer. The excitation of this system was a Square wave voltage, where experiments were realized in two ways: considering planar coil as primary and observing responses on secondary being ring coil (direct system) and the inverse (ring coil as primary and planar coil as secondary-inverted system). In this study, a phenomenon not common in literature on system response is analyzed, showing efiects of changes on transfer function in both cases when varying turn numbers of each coil and several variations on responses due to changes on resistances, parasitic capacitances, self and mutual inductances of the coils. The uncommon phenomenon appears as modulated response on speciflc turn ratio. The obtained results can be used to researches in areas as power electronics and pulse transformers.
Mohammad Saleh Moonesan - One of the best experts on this subject based on the ideXlab platform.
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Impact of charge accumulation on insulation films subjected to unipolar and bipolar Square Waves
IEEE Transactions on Dielectrics and Electrical Insulation, 2017Co-Authors: Mohammad Saleh Moonesan, Shesha H. Jayaram, Edward A. CherneyAbstract:The paper presents the results of surface charge measurements on insulation film samples with different surface resistivities. Polytetrafluoroethylene (PTFE) and Nylon 6 (PA6) as well as mica paper subjected to unipolar and bipolar Square Waves at different switching frequencies. The experimental data are presented to explain the differences observed in the times-to-failure of turn insulation when aged using unipolar and bipolar Square Waves. Time-to-failure experiments and COMSOL® simulations are used to estimate the accumulated charge on the surface of insulation films with different surface resistivities.
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Study on form-wound machine turn insulation subjected to unipolar and bipolar Square Waves
IEEE Transactions on Dielectrics and Electrical Insulation, 2016Co-Authors: Mohammad Saleh Moonesan, Shesha H. Jayaram, Edward A. CherneyAbstract:The paper examines the time-to-failure of enameled form-wound machine turn insulation subjected to unipolar and bipolar Square Waves at different switching frequencies. Partial discharge under the same Square wave parameters are also reported using a point-to-plane geometry from which the measured PD features are related to the time-to-failure results of the turn insulation. The results show that the life of enameled turn insulation is considerably longer under bipolar Square Waves than for unipolar Waves and that turn insulation lifetime is related to the power of the partial discharges. In addition, a frequency threshold in the time-to-failure results is observed corresponding to a decrease in PD power and the development of surface space charge that affects the PD features is discussed.
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time to failure of medium voltage form wound machine turn insulation stressed by unipolar Square Waves
IEEE Transactions on Dielectrics and Electrical Insulation, 2015Co-Authors: Mohammad Saleh Moonesan, S H Jayaram, E A CherneyAbstract:The lifespans of enamelled turn insulation samples are studied when stressed with Square Waves characterized by different rise times, duty cycles, switching frequencies, and applied voltages. Partial discharge activities under these test conditions have also been recorded using an RF antenna in an effort to correlate the time to breakdown with material degradation under fast repetitive pulse aging. The aging and PD features were independent of rise time for a 50 % duty cycle; however, slightly faster times to failure were observed at a 15 % duty cycle for the faster rise times, for the considered range. The higher duty cycle and the higher number of applied cycles accelerated the aging.
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Effect of voltage rise time on time-to-failure of form-wound stator coil enamelled turn insulation
2014 IEEE Electrical Insulation Conference (EIC), 2014Co-Authors: Mohammad Saleh Moonesan, Shesha Jayaram, Edward Cherney, Ramtin OmranipourAbstract:The paper presents the results of aging of medium voltage stator coil enamelled turn insulation under Square Waves having rise times of 270 ns and 4.5 μs. Unipolar Square Waves having a peak voltage of 2.5 kV and a switching frequency of 3 kHz were applied to enamelled wire samples while measuring online partial discharge. A two-parameter Weibull distribution was employed for analysis of the effect of rise time on insulation life. The tests were repeated at 6 kV peak with duty cycles of 15% and 50% for both rise times. The analysis indicates that insulation life is dependent on voltage rise time only when the DC component of the wave is short.
David W. Sukow - One of the best experts on this subject based on the ideXlab platform.
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simple and complex Square Waves in an edge emitting diode laser with polarization rotated optical feedback
Physical Review E, 2010Co-Authors: Athanasios Gavrielides, David W. Sukow, Guinevere Burner, Taylor Mclachlan, J Miller, Jake AmonetteAbstract:Numerical and experimental results are presented for an edge-emitting diode laser with delayed optical feedback, where the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. We examine the bifurcation structure and dynamics that give rise to a class of periodic, polarization-modulated solutions, the simplest of which is a Square wave solution with a period related to but longer than twice the external cavity roundtrip time. Such solutions typically emerge when the feedback is strong and the differential losses in the normally unsupported polarization mode are small. We also observe more complex waveforms that maintain the same periodicity.
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asymmetric Square Waves in mutually coupled semiconductor lasers with orthogonal optical injection
Physical Review E, 2010Co-Authors: David W. Sukow, Thomas Erneux, Athanasios Gavrielides, Benjamin Mooneyham, Karen Lee, Jake Mckay, Josiah W DavisAbstract:Two edge-emitting lasers mutually coupled through orthogonal optical injection exhibit Square-wave oscillations in their polarization modes. The TE and TM modes within each individual laser are always in antiphase, but the TE mode of one laser leads the TM of the other by the one-way time of flight between lasers. The duty cycle of the Square Waves is tunable with pump current and coupling strength, while the total period remains close to the roundtrip time. Numerical simulations give similar results and reveal the role of noise in stabilizing the oscillations.
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Asymmetric Square-Waves in mutually coupled semiconductor lasers
Semiconductor Lasers and Laser Dynamics III, 2008Co-Authors: David W. Sukow, Thomas Erneux, Athanasios Gavrielides, Josiah W Davis, Makhosazana Z.makhosazana Dube, Saneliso Mabuza, Russell TrimmerAbstract:Two edge-emitting lasers coupled through polarization-rotated optical injection exhibit Square-wave oscillations provided the roundtrip time from laser to laser and back is sufficiently large. If the mutual coupling between the lasers is relatively weak, the two plateaus of the Square-Waves exhibit different durations even though the total period remains close to the roundtrip time. This asymmetry progressively disappears as the feedback strength is increased. The experimental observations are confirmed by numerical simulations. The simulations also reveal that the Square-wave regimes appear through a series of complex bifurcations and that a sufficiently large roundtrip time is needed.