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Anticlockwise

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Michael J. Adams – One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear Gain and Optical Bistability in Novel GaInNAs Vertical-Cavity Semiconductor Optical Amplifiers
    2018 Asia Communications and Photonics Conference (ACP), 2018
    Co-Authors: Michael J. Adams, Dexin Wu

    Abstract:

    The nonlinear gain properties of GaInNAs vertical-cavity semiconductor optical amplifier operated in reflection mode are reported. A step-like differential gain and the Anticlockwise bistability are predicted. The dependence of the optical bistability on the applied current and phase detuning are analyzed.

  • Two-Wavelength Switching With a 1550 nm VCSEL Under Single Orthogonal Optical Injection
    IEEE Journal of Selected Topics in Quantum Electronics, 2008
    Co-Authors: A. Hurtado, I.d. Henning, Michael J. Adams

    Abstract:

    We report the first experimental observation of three distinct forms of two-wavelength switching (clockwise, Anticlockwise, and butterfly) for a 1550 nm vertical cavity surface emitting laser (VCSEL) operated just above threshold and subject to orthogonally polarized optical injection. The spectrum of the device exhibits two modes, a main mode emitting in a “parallel” polarization and a subsidiary “`orthogonal” polarized mode. Low input-power switching of the emission wavelength of the VCSEL by an orthogonally polarized external optical signal injected to the long-wavelength side of the subsidiary mode is observed. Clockwise switching and bistability of the main lasing mode with very high on-off contrast ratio has been measured in all cases. Three different switching shapes: Anticlockwise, butterfly, and clockwise, have been measured for the output of the optically injected VCSEL. This diversity of switching behavior with a 1550 nm VCSEL subject to optical injection offers promise for the use of these devices in all-optical switching/routing as well as optical interconnect applications.

  • Optical Bistability and Nonlinear Gain in a 1550 nm-Vertical Cavity Semiconductor Optical Amplifier (VCSOA) with High On-Off Contrast Ratio
    2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
    Co-Authors: A. Hurtado, I.d. Henning, Michael J. Adams

    Abstract:

    This paper reports on the experimental observation of power and wavelength optical bistability (OB) and nonlinear gain in a 1550 nm- vertical cavity semiconductor optical amplifier (VCSOA) biased just below threshold and operated in reflection. Two different shapes of power and wavelength OB and nonlinear gain, Anticlockwise and clockwise, have been experimentally observed, both with high on-off contrast ratio.

Ondrej Lexa – One of the best experts on this subject based on the ideXlab platform.

  • Late Palaeozoic palaeomagnetic and tectonic constraints for amalgamation of Pangea supercontinent in the European Variscan belt
    Earth-Science Reviews, 2018
    Co-Authors: J B Edel, Ondrej Lexa, Karel Schulmann, Jean Marc Lardeaux

    Abstract:

    This paper provides a review of the evolution of palaeomagnetic directions and sequence of tectonic events in the European Variscan belt during Late Palaeozoic times. These data are correlated with palaeomagnetic records from Gondwana and Baltica in order to provide a large-scale geodynamic framework during the Carboniferous to Permian. The Early Carboniferous palaeomagnetic records reported mainly from the Rhenohercynian and Saxothuringian magmatic arcs indicate a 70° Anticlockwise rotation, while Late Carboniferous to Permian magnetic directions from various rocks of western and central Europe are consistent with 120° clockwise rotation of the eastern and central parts of the Variscan belt. Our review of the chronology of tectonic events is based on a robust database of geochronologically constrained deformation, metamorphic and magmatic events, which allow discretizing the 80 Ma long orogenic evolution into five principal events. In this scenario, the Variscan belt can be regarded as a linear sub-plate, isolated from Gondwana and Laurussia by the Rhenohercynian and Palaeotethysian oceans during Devonian times. This linear composite belt was segmented by transform faults and boundaries in the Late Devonian to Early Carboniferous times (360–335 Ma) during progressive E–W closure of Rhenohercynian ocean synchronously with collision between Saxothuringian and Moldanubian blocks. Subsequent relocation of subduction to the northern boundary Palaeotethysian ocean was responsible for N–S shortening almost orthogonal to the ancient sub-plate N–S elongation at around 335–325 Ma. This deformation resulted in dextral reactivation of transform boundaries associated with Anticlockwise rotation of intermittent blocks. At the end of this rotation, the faults were parallelized to the Teysseire-Tornquist zone – the southern margin of Baltica, while the lozenge-shaped blocks of the former Variscan sub-plate were further shortened during continuous contraction. This evolution can fully explain the ≈ 70° Anticlockwise rotation from Cn3 to Cn2 palaeomagnetic directions, which are regarded as successive Carboniferous magnetizations. Subsequently, the Variscan belt suffered a giant transtensional event from 325 to 310 Ma that was related to the development of extensional syn-magmatic core complexes over the whole belt and significant dextral reactivation of earlier NW–SE trending transform faults. This extensional event was associated with important tilts recorded by Cp magnetic overprint resulting from a major thermally induced remagnetization. During this event new sets of sinistral transfer NNE–SSW trending faults originated, that partly reactivated boundaries of the principal tectonic zones. Blocks delimited by second-order sinistral and first-order dextral faults, then rotated in a clockwise manner by ≈ 80°. The whole system subsequently suffered a period of NNE–SSW shortening that affected the Variscan belt namely along the former Laurussian and former Variscan sub-plate contact in the north and in the south, where the giant Cantabrian orocline developed at around 310–300 Ma due to hard collision with Gondwana. This deformation is associated with the clockwise rotation of Laurussia together with the accreted northern sector of the Variscan belt, and the Anticlockwise of Gondwana. This clockwise 30° rotation is achieved by A1 remagnetizations, while the southern part of Iberia suffered Anticlockwise rotation. The final stage of rapid clockwise rotation affecting the northern limb of the Iberian Arc including Corsica and Sardinia is attributed to giant N–S extension affecting the whole Variscan belt at the onset of Permo-Triassic opening of the Tethys ocean. This complex evolution is regarded as a result of the readjustment of inhomogeneous and thermally and mechanically instable mobile space in between reorganizing the Gondwana and Laurussia megaplates and the opening of the Palaeotethys ocean during the final stages of formation of the Pangea supercontinent. Finally, the palaeomagnetically constrained rotations and tectonic evolution of the Variscan belt are explained using a pinned model of “internal” and “external” rotations of blocks driven by activation of dextral shear zones by N–S compression and E–W transtension in particular.

  • palaeomagnetic and structural constraints on 90 Anticlockwise rotation in sw mongolia during the permo triassic implications for altaid oroclinal bending preliminary palaeomagnetic results
    Journal of Asian Earth Sciences, 2014
    Co-Authors: J B Edel, Karel Schulmann, Pavel Hanžl, Ondrej Lexa

    Abstract:

    Abstract New and published paleomagnetic measurements from Trans Altai and South Gobi zones in south Mongolia document large tectonic motions in between Late Carboniferous and Triassic. Magnetic inclinations confirm equatorial position of south Mongolian terranes in Late Carboniferous–Permian times. The evolution of magnetic declinations indicates 90° Anticlockwise rotation in between latest Carboniferous and Early Triassic of all studied tectonic units around the Eulerian pole located close to axis of Mongolian orocline. The Anticlockwise rotation continues in Triassic being accompanied by a major drift to the north. The structural and published geochronological data suggest Carboniferous E–W shortening of the whole region resulting in N–S trend of all continental and oceanic geological units followed by orthogonal N–S shortening during Late Permian to Early Jurassic. Both paleomagnetic and geological data converge in a tectonic model of oroclinal bending of Mongolian ribbon continent, westerly back arc oceanic domain and Mongol–Okhotsk subduction zone to the east. The oroclinal bending model is consistent with the coincidence of the Eulerian pole of rotation with the structural axis of Mongolian orocline. In addition, the Mesozoic collisional tectonics is reflected by late remagnetizations due to formation of wide deformation fronts and hydrothermal activity.

  • Palaeomagnetic and structural constraints on 90° Anticlockwise rotation in SW Mongolia during the Permo–Triassic: Implications for Altaid oroclinal bending. Preliminary palaeomagnetic results
    Journal of Asian Earth Sciences, 2014
    Co-Authors: J B Edel, Karel Schulmann, Pavel Hanžl, Ondrej Lexa

    Abstract:

    Abstract New and published paleomagnetic measurements from Trans Altai and South Gobi zones in south Mongolia document large tectonic motions in between Late Carboniferous and Triassic. Magnetic inclinations confirm equatorial position of south Mongolian terranes in Late Carboniferous–Permian times. The evolution of magnetic declinations indicates 90° Anticlockwise rotation in between latest Carboniferous and Early Triassic of all studied tectonic units around the Eulerian pole located close to axis of Mongolian orocline. The Anticlockwise rotation continues in Triassic being accompanied by a major drift to the north. The structural and published geochronological data suggest Carboniferous E–W shortening of the whole region resulting in N–S trend of all continental and oceanic geological units followed by orthogonal N–S shortening during Late Permian to Early Jurassic. Both paleomagnetic and geological data converge in a tectonic model of oroclinal bending of Mongolian ribbon continent, westerly back arc oceanic domain and Mongol–Okhotsk subduction zone to the east. The oroclinal bending model is consistent with the coincidence of the Eulerian pole of rotation with the structural axis of Mongolian orocline. In addition, the Mesozoic collisional tectonics is reflected by late remagnetizations due to formation of wide deformation fronts and hydrothermal activity.

J B Edel – One of the best experts on this subject based on the ideXlab platform.

  • Late Palaeozoic palaeomagnetic and tectonic constraints for amalgamation of Pangea supercontinent in the European Variscan belt
    Earth-Science Reviews, 2018
    Co-Authors: J B Edel, Ondrej Lexa, Karel Schulmann, Jean Marc Lardeaux

    Abstract:

    This paper provides a review of the evolution of palaeomagnetic directions and sequence of tectonic events in the European Variscan belt during Late Palaeozoic times. These data are correlated with palaeomagnetic records from Gondwana and Baltica in order to provide a large-scale geodynamic framework during the Carboniferous to Permian. The Early Carboniferous palaeomagnetic records reported mainly from the Rhenohercynian and Saxothuringian magmatic arcs indicate a 70° Anticlockwise rotation, while Late Carboniferous to Permian magnetic directions from various rocks of western and central Europe are consistent with 120° clockwise rotation of the eastern and central parts of the Variscan belt. Our review of the chronology of tectonic events is based on a robust database of geochronologically constrained deformation, metamorphic and magmatic events, which allow discretizing the 80 Ma long orogenic evolution into five principal events. In this scenario, the Variscan belt can be regarded as a linear sub-plate, isolated from Gondwana and Laurussia by the Rhenohercynian and Palaeotethysian oceans during Devonian times. This linear composite belt was segmented by transform faults and boundaries in the Late Devonian to Early Carboniferous times (360–335 Ma) during progressive E–W closure of Rhenohercynian ocean synchronously with collision between Saxothuringian and Moldanubian blocks. Subsequent relocation of subduction to the northern boundary Palaeotethysian ocean was responsible for N–S shortening almost orthogonal to the ancient sub-plate N–S elongation at around 335–325 Ma. This deformation resulted in dextral reactivation of transform boundaries associated with Anticlockwise rotation of intermittent blocks. At the end of this rotation, the faults were parallelized to the Teysseire-Tornquist zone – the southern margin of Baltica, while the lozenge-shaped blocks of the former Variscan sub-plate were further shortened during continuous contraction. This evolution can fully explain the ≈ 70° Anticlockwise rotation from Cn3 to Cn2 palaeomagnetic directions, which are regarded as successive Carboniferous magnetizations. Subsequently, the Variscan belt suffered a giant transtensional event from 325 to 310 Ma that was related to the development of extensional syn-magmatic core complexes over the whole belt and significant dextral reactivation of earlier NW–SE trending transform faults. This extensional event was associated with important tilts recorded by Cp magnetic overprint resulting from a major thermally induced remagnetization. During this event new sets of sinistral transfer NNE–SSW trending faults originated, that partly reactivated boundaries of the principal tectonic zones. Blocks delimited by second-order sinistral and first-order dextral faults, then rotated in a clockwise manner by ≈ 80°. The whole system subsequently suffered a period of NNE–SSW shortening that affected the Variscan belt namely along the former Laurussian and former Variscan sub-plate contact in the north and in the south, where the giant Cantabrian orocline developed at around 310–300 Ma due to hard collision with Gondwana. This deformation is associated with the clockwise rotation of Laurussia together with the accreted northern sector of the Variscan belt, and the Anticlockwise of Gondwana. This clockwise 30° rotation is achieved by A1 remagnetizations, while the southern part of Iberia suffered Anticlockwise rotation. The final stage of rapid clockwise rotation affecting the northern limb of the Iberian Arc including Corsica and Sardinia is attributed to giant N–S extension affecting the whole Variscan belt at the onset of Permo-Triassic opening of the Tethys ocean. This complex evolution is regarded as a result of the readjustment of inhomogeneous and thermally and mechanically instable mobile space in between reorganizing the Gondwana and Laurussia megaplates and the opening of the Palaeotethys ocean during the final stages of formation of the Pangea supercontinent. Finally, the palaeomagnetically constrained rotations and tectonic evolution of the Variscan belt are explained using a pinned model of “internal” and “external” rotations of blocks driven by activation of dextral shear zones by N–S compression and E–W transtension in particular.

  • palaeomagnetic and structural constraints on 90 Anticlockwise rotation in sw mongolia during the permo triassic implications for altaid oroclinal bending preliminary palaeomagnetic results
    Journal of Asian Earth Sciences, 2014
    Co-Authors: J B Edel, Karel Schulmann, Pavel Hanžl, Ondrej Lexa

    Abstract:

    Abstract New and published paleomagnetic measurements from Trans Altai and South Gobi zones in south Mongolia document large tectonic motions in between Late Carboniferous and Triassic. Magnetic inclinations confirm equatorial position of south Mongolian terranes in Late Carboniferous–Permian times. The evolution of magnetic declinations indicates 90° Anticlockwise rotation in between latest Carboniferous and Early Triassic of all studied tectonic units around the Eulerian pole located close to axis of Mongolian orocline. The Anticlockwise rotation continues in Triassic being accompanied by a major drift to the north. The structural and published geochronological data suggest Carboniferous E–W shortening of the whole region resulting in N–S trend of all continental and oceanic geological units followed by orthogonal N–S shortening during Late Permian to Early Jurassic. Both paleomagnetic and geological data converge in a tectonic model of oroclinal bending of Mongolian ribbon continent, westerly back arc oceanic domain and Mongol–Okhotsk subduction zone to the east. The oroclinal bending model is consistent with the coincidence of the Eulerian pole of rotation with the structural axis of Mongolian orocline. In addition, the Mesozoic collisional tectonics is reflected by late remagnetizations due to formation of wide deformation fronts and hydrothermal activity.

  • Palaeomagnetic and structural constraints on 90° Anticlockwise rotation in SW Mongolia during the Permo–Triassic: Implications for Altaid oroclinal bending. Preliminary palaeomagnetic results
    Journal of Asian Earth Sciences, 2014
    Co-Authors: J B Edel, Karel Schulmann, Pavel Hanžl, Ondrej Lexa

    Abstract:

    Abstract New and published paleomagnetic measurements from Trans Altai and South Gobi zones in south Mongolia document large tectonic motions in between Late Carboniferous and Triassic. Magnetic inclinations confirm equatorial position of south Mongolian terranes in Late Carboniferous–Permian times. The evolution of magnetic declinations indicates 90° Anticlockwise rotation in between latest Carboniferous and Early Triassic of all studied tectonic units around the Eulerian pole located close to axis of Mongolian orocline. The Anticlockwise rotation continues in Triassic being accompanied by a major drift to the north. The structural and published geochronological data suggest Carboniferous E–W shortening of the whole region resulting in N–S trend of all continental and oceanic geological units followed by orthogonal N–S shortening during Late Permian to Early Jurassic. Both paleomagnetic and geological data converge in a tectonic model of oroclinal bending of Mongolian ribbon continent, westerly back arc oceanic domain and Mongol–Okhotsk subduction zone to the east. The oroclinal bending model is consistent with the coincidence of the Eulerian pole of rotation with the structural axis of Mongolian orocline. In addition, the Mesozoic collisional tectonics is reflected by late remagnetizations due to formation of wide deformation fronts and hydrothermal activity.