The Experts below are selected from a list of 47637 Experts worldwide ranked by ideXlab platform
Oleg D Lavrentovich - One of the best experts on this subject based on the ideXlab platform.
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Nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Oleg D LavrentovichAbstract:We study a Nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field $\mathbf{E}$ modifies the tensor order parameter but does not change the orientation of the optic axis (director $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$. The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) Nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of Nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of Nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of Nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of Nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (Nanosecond) changes in optical characteristics, such as birefringence.
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Nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Bingxiang Li, Oleg D LavrentovichAbstract:: We study a Nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N ). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to N . The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) Nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of Nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of Nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of Nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of Nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (Nanosecond) changes in optical characteristics, such as birefringence.
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electro optic switching of dielectrically negative nematic through Nanosecond electric modification of order parameter
Applied Physics Letters, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Shaobin Liu, Oleg D LavrentovichAbstract:We present experimental studies of Nanosecond electric modification of the order parameter (NEMOP) in a variety of nematic materials with negative dielectric anisotropy. The study demonstrates that NEMOP enables a large amplitude of fast (Nanoseconds) electro-optic response with the field-induced birefringence on the order of 0.01 and a figure of merit (FoM) on the order of 104 μm2/s; the latter is orders of magnitude higher than the FoM of the Frederiks effect traditionally used in electro-optic nematic devices. The amplitude of the NEMOP response is generally stronger in nematics with larger dielectric anisotropy and with higher natural (field-free) birefringence.
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electro optic switching of dielectrically negative nematic through Nanosecond electric modification of order parameter nemop
arXiv: Optics, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Shaobin Liu, Oleg D LavrentovichAbstract:We present experimental studies of Nanosecond electric modification of the order parameter (NEMOP) in a variety of nematic materials with negative dielectric anisotropy. The study demonstrates that NEMOP enables a large amplitude of fast (Nanoseconds) electro-optic response with the field-induced birefringence on the order of 0.01 and a figure of merit (FoM) on the order of $10^4$ $\mu $m$^2/$s; the latter is orders of magnitude higher than the FoM of the Frederiks effect traditionally used in electro-optic nematic devices. The amplitude of the NEMOP response is generally stronger in nematics with larger dielectric anisotropy and with higher natural (field-free) birefringence.
Volodymyr Borshch - One of the best experts on this subject based on the ideXlab platform.
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Nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Oleg D LavrentovichAbstract:We study a Nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field $\mathbf{E}$ modifies the tensor order parameter but does not change the orientation of the optic axis (director $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$. The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) Nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of Nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of Nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of Nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of Nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (Nanosecond) changes in optical characteristics, such as birefringence.
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Nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Bingxiang Li, Oleg D LavrentovichAbstract:: We study a Nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N ). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to N . The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) Nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of Nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of Nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of Nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of Nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (Nanosecond) changes in optical characteristics, such as birefringence.
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electro optic switching of dielectrically negative nematic through Nanosecond electric modification of order parameter
Applied Physics Letters, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Shaobin Liu, Oleg D LavrentovichAbstract:We present experimental studies of Nanosecond electric modification of the order parameter (NEMOP) in a variety of nematic materials with negative dielectric anisotropy. The study demonstrates that NEMOP enables a large amplitude of fast (Nanoseconds) electro-optic response with the field-induced birefringence on the order of 0.01 and a figure of merit (FoM) on the order of 104 μm2/s; the latter is orders of magnitude higher than the FoM of the Frederiks effect traditionally used in electro-optic nematic devices. The amplitude of the NEMOP response is generally stronger in nematics with larger dielectric anisotropy and with higher natural (field-free) birefringence.
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electro optic switching of dielectrically negative nematic through Nanosecond electric modification of order parameter nemop
arXiv: Optics, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Shaobin Liu, Oleg D LavrentovichAbstract:We present experimental studies of Nanosecond electric modification of the order parameter (NEMOP) in a variety of nematic materials with negative dielectric anisotropy. The study demonstrates that NEMOP enables a large amplitude of fast (Nanoseconds) electro-optic response with the field-induced birefringence on the order of 0.01 and a figure of merit (FoM) on the order of $10^4$ $\mu $m$^2/$s; the latter is orders of magnitude higher than the FoM of the Frederiks effect traditionally used in electro-optic nematic devices. The amplitude of the NEMOP response is generally stronger in nematics with larger dielectric anisotropy and with higher natural (field-free) birefringence.
Sergij V Shiyanovskii - One of the best experts on this subject based on the ideXlab platform.
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Nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Oleg D LavrentovichAbstract:We study a Nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field $\mathbf{E}$ modifies the tensor order parameter but does not change the orientation of the optic axis (director $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$. The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) Nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of Nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of Nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of Nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of Nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (Nanosecond) changes in optical characteristics, such as birefringence.
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Nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Bingxiang Li, Oleg D LavrentovichAbstract:: We study a Nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N ). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to N . The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) Nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of Nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of Nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of Nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of Nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (Nanosecond) changes in optical characteristics, such as birefringence.
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electro optic switching of dielectrically negative nematic through Nanosecond electric modification of order parameter
Applied Physics Letters, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Shaobin Liu, Oleg D LavrentovichAbstract:We present experimental studies of Nanosecond electric modification of the order parameter (NEMOP) in a variety of nematic materials with negative dielectric anisotropy. The study demonstrates that NEMOP enables a large amplitude of fast (Nanoseconds) electro-optic response with the field-induced birefringence on the order of 0.01 and a figure of merit (FoM) on the order of 104 μm2/s; the latter is orders of magnitude higher than the FoM of the Frederiks effect traditionally used in electro-optic nematic devices. The amplitude of the NEMOP response is generally stronger in nematics with larger dielectric anisotropy and with higher natural (field-free) birefringence.
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electro optic switching of dielectrically negative nematic through Nanosecond electric modification of order parameter nemop
arXiv: Optics, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Shaobin Liu, Oleg D LavrentovichAbstract:We present experimental studies of Nanosecond electric modification of the order parameter (NEMOP) in a variety of nematic materials with negative dielectric anisotropy. The study demonstrates that NEMOP enables a large amplitude of fast (Nanoseconds) electro-optic response with the field-induced birefringence on the order of 0.01 and a figure of merit (FoM) on the order of $10^4$ $\mu $m$^2/$s; the latter is orders of magnitude higher than the FoM of the Frederiks effect traditionally used in electro-optic nematic devices. The amplitude of the NEMOP response is generally stronger in nematics with larger dielectric anisotropy and with higher natural (field-free) birefringence.
Svetlana Starikovskaia - One of the best experts on this subject based on the ideXlab platform.
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electric field vector measurements via Nanosecond electric field induced second harmonic generation
Optics Letters, 2020Co-Authors: Tat Loon Chng, Benjamin M Goldberg, Maya Naphade, Igor V Adamovich, Svetlana StarikovskaiaAbstract:Electric-field-induced second-harmonic generation, or E-FISH, has received renewed interest as a nonintrusive tool for probing electric fields in gas discharges and plasmas using ultrashort laser pulses. An important contribution of this work lies in establishing that the E-FISH method works effectively in the Nanosecond regime, yielding field sensitivities of about a kV/cm at atmospheric pressure from a 16 ns pulse. This is expected to broaden its applicability within the plasma community, given the wider access to conventional Nanosecond laser sources. A Pockels-cell-based pulse-slicing scheme, which may be readily integrated with such Nanosecond laser systems, is shown to be a complementary and cost-effective option for improving the time resolution of the electric field measurement. Using this scheme, a time resolution of ∼3 ns is achieved, without any detriment to the signal sensitivity. This could prove invaluable for nonequilibrium plasma applications, where time resolution of a few Nanoseconds or less is often critical. Finally, we take advantage of the field vector sensitivity of the E-FISH signal to demonstrate simultaneous measurements of both the horizontal and vertical components of the electric field.
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long lived plasma and fast quenching of n2 c3π u by electrons in the afterglow of a Nanosecond capillary discharge in nitrogen
Plasma Sources Science and Technology, 2016Co-Authors: N D Lepikhin, N A Popov, A V Klochko, Svetlana StarikovskaiaAbstract:Quenching of electronically excited nitrogen state, ##IMG## [http://ej.iop.org/images/0963-0252/25/4/045003/psstaa2269ieqn003.gif] \textN_2≤ft(\textC^3Π_u,v^\prime=0\right) , in the afterglow of Nanosecond capillary discharge in pure nitrogen is studied. It is found experimentally that an additional collisional mechanism appears and dominates at high specific deposited energies leading to the anomalously fast quenching of the ##IMG## [http://ej.iop.org/images/0963-0252/25/4/045003/psstaa2269ieqn004.gif] \textN_2≤ft(\textC^3Π_u\right) in the afterglow. On the basis of obtained experimental data and of the analysis of possible quenching agents, it is concluded that the anomalously fast deactivation of the ##IMG## [http://ej.iop.org/images/0963-0252/25/4/045003/psstaa2269ieqn005.gif] \textN_2≤ft(\textC^3Π_u\right) can be explained by quenching by electrons. Long-lived plasma at time scale of hundreds Nanoseconds after the end of the pulse is observed. High electron densities, about 10 14 cm в3 at 27 mbar, are sustained by reactions of associative ionization. Kinetic 1D numerical modeling and comparison of calculated results with experimentally measured electric fields in the second high-voltage pulse 250 ns after the initial pulse, and electron density measurements in the afterglow confirm the validity of the suggested mechanism.
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a Nanosecond surface dielectric barrier discharge in air at high pressures and different polarities of applied pulses transition to filamentary mode
Plasma Sources Science and Technology, 2014Co-Authors: S A Stepanyan, Yu A Starikovskiy, N A Popov, Svetlana StarikovskaiaAbstract:The development of a Nanosecond surface dielectric barrier discharge in air at pressures 1–6 bar is studied. At atmospheric pressure, the discharge develops as a set of streamers starting synchronously from the high-voltage electrode and propagating along the dielectric layer. Streamers cover the dielectric surface creating a ‘quasi-uniform’ plasma layer. At high pressures and high voltage amplitudes on the cathode, filamentation of the discharge is observed a few Nanoseconds after the discharge starts. Parameters of the observed ‘streamers-to-filaments’ transition are measured; physics of transition is discussed on the basis of theoretical estimates and numerical modeling. Ionization-heating instability on the boundary of the cathode layer is suggested as a mechanism of filamentation.
Canan Atilgan - One of the best experts on this subject based on the ideXlab platform.
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Nanosecond motions in proteins impose bounds on the timescale distributions of local dynamics
Biophysical Journal, 2009Co-Authors: Osman Burak Okan, Ali Rana Atilgan, Canan AtilganAbstract:We elucidate the physics of protein dynamical transition via 10–100-ns molecular dynamics simulations at temperatures spanning 160–300 K. By tracking the energy fluctuations, we show that the protein dynamical transition is marked by a crossover from nonstationary to stationary processes that underlie the dynamics of protein motions. A two-timescale function captures the nonexponential character of backbone structural relaxations. One timescale is attributed to the collective segmental motions and the other to local relaxations. The former is well defined by a single-exponential, Nanosecond decay, operative at all temperatures. The latter is described by a set of processes that display a distribution of timescales. Although their average remains on the picosecond timescale, the distribution is markedly contracted at the onset of the transition. It is shown that the collective motions impose bounds on timescales spanned by local dynamical processes. The nonstationary character below the transition implicates the presence of a collection of substates whose interactions are restricted. At these temperatures, a wide distribution of local-motion timescales, extending beyond that of Nanoseconds, is observed. At physiological temperatures, local motions are confined to timescales faster than Nanoseconds. This relatively narrow window makes possible the appearance of multiple channels for the backbone dynamics to operate.
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Nanosecond motions in proteins impose bounds on the timescale distributions of local dynamics
arXiv: Quantitative Methods, 2009Co-Authors: Osman Burak Okan, Ali Rana Atilgan, Canan AtilganAbstract:We elucidate the physics of the dynamical transition via 10-100ns molecular dynamics simulations at temperatures spanning 160-300K. By tracking the energy fluctuations, we show that the protein dynamical transition is marked by a cross-over from piecewise stationary to stationary processes that underlie the dynamics of protein motions. A two-time-scale function captures the non-exponential character of backbone structural relaxations. One is attributed to the collective segmental motions and the other to local relaxations. The former is well-defined by a single-exponential, Nanosecond decay, operative at all temperatures. The latter is described by a set of processes that display a distribution of time-scales. Though their average remains on the picosecond time-scale, the distribution is markedly contracted at the onset of the transition. The collective motions are shown to impose bounds on time-scales spanned by local dynamical processes. The piecewise stationary character below the transition implicates the presence of a collection of sub-states whose interactions are restricted. At these temperatures, a wide distribution of local motion time-scales, extending beyond that of Nanoseconds is observed. At physiological temperatures, local motions are confined to time-scales faster than Nanoseconds. This relatively narrow window makes possible the appearance of multiple channels for the backbone dynamics to operate.
