The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Ranganathan Shashidhar - One of the best experts on this subject based on the ideXlab platform.
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electroclinic liquid crystals with large Induced Tilt angle and small layer contraction
Physical Review E, 2000Co-Authors: Mark S Spector, Jawad Naciri, B. T. Weslowski, Paul A Heiney, David B Holt, Ranganathan ShashidharAbstract:Optical and x-ray scattering studies of a chiral, organosiloxane smectic-A liquid crystal indicate a large field Induced optical Tilt of up to 31 degrees accompanied by a very small contraction of the smectic layers. This result suggests that the molecules have a nonzero Tilt even with no applied field, and that the primary effect of the field is to induce long range order in the direction of the molecular Tilt.
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Advances in liquid crystals for gray-scale applications
electronic imaging, 1999Co-Authors: Jawad Naciri, Ranganathan Shashidhar, B. T. Weslowski, Charmaine D. Wilson, B. R. RatnaAbstract:Chiral smectic A electroclinic liquid crystalline materials are prime candidates for electrooptic applications because of their gray scale capability and fast dynamic response. The evolution of this technology greatly depends on the development of chiral smectic A materials with large Induced Tilt angles, field-independent fast switching times and a broad operating temperature range. We report in this paper the physical properties of a series of liquid crystal materials. Features of this series of materials are broad smectic A phase range and large Induced Tilt angles. Such large electroclinic coefficients make these materials good candidates of the development of silicon based reflective displays. Comparison of the electrooptic performance of the materials in SmA mesophase will be discussed.
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Electro-optic performance of electroclinic materials with large Induced Tilt angle
Liquid Crystal Materials Devices and Applications III, 1994Co-Authors: B. R. Ratna, Gregory P. Crawford, Jawad Naciri, Ranganathan ShashidharAbstract:The electric field Induced Tilt angles and the corresponding optical transmission properties are presented for two homologs and a mixture which exhibit a strong electroclinic effect at ambient temperatures. Tilt angles as large as 15 degree(s) are reported. The relationship between the molecular Tilt angle and the transmission properties are emphasized.
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Electroclinic materials with large Induced Tilt angles
Ferroelectrics, 1993Co-Authors: B. R. Ratna, Gregory P. Crawford, S. Krishna Prasad, Jawad Naciri, Patrick Keller, Ranganathan ShashidharAbstract:Abstract The electroclinic effect in the smectic A phase of three successive even members of a homologous series has been studied. They exhibit large field-Induced Tilt angles up to 15° for an applied electric field of 10V/μm over a wide temperature range. The Induced Tilt angle increases with increasing alkyl chain length (n) of the non-chiral end of the molecule. On cooling from high temperatures, the Induced Tilt angle θ initially increases monotonically, but at lower temperatures, the trend is reversed. This observed anomaly is more pronounced for the higher homolog and at higher electric fields. A similar anomaly is also seen in the variation of the electroclinic coefficient evaluated at low fields. The relationship between the electroclinic Tilt angle and molecular structure is discussed.
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Fast switching ferroelectric side-chain liquid-crystalline polymer and copolymer
Liquid Crystals, 1991Co-Authors: Jawad Naciri, S. Pfeiffer, Ranganathan ShashidharAbstract:Abstract New ferroelectric side-chain liquid-crystalline polymers, a copolymer and a homopolymer, with siloxane backbone and a triaromatic mesogen as the side group have been synthesized. The materials exhibit a chiral smectic C phase over a large temperature range extending to room temperature. They possess high values of spontaneous polarization: 105 nC cm−2 for the homopolymer and 180 nC cm−2 for the copolymer. The electro-optic switching time in the chiral smectic C phase is extremely fast (150 μs). In the smectic A phase, an electroclinic effect with switching times less than 100 μs and with field Induced Tilt angles of 18° is observed.
Jawad Naciri - One of the best experts on this subject based on the ideXlab platform.
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Anomalous dependence of response time on the electric field in an electroclinic liquid crystal with large Induced Tilt and polarization
Applied Physics Letters, 2009Co-Authors: U. Manna, Jang-kun Song, Jawad NaciriAbstract:We investigate the response time of an electroclinic liquid crystal with large Induced Tilt and polarization (de Vries smectic A∗). The response time is found to increase with the increase in electric field up to a threshold value in contrast with the general case of a decrease with field. This behavior is unusual and contrasts with that observed for a conventional smectic-A∗ phase. The anomalous behavior is explained by the Langevin process of the director reorientation by assuming an increase in the effective dipole moment (μeff) with field. The response time decreases with the increase in temperature in the smectic-A∗ phase. We find the existence of a finite correlation length of a few tens of nm which in both temperature and field dependent.
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Anisotropic actuation in electroclinic liquid crystal elastomers
Applied Physics Letters, 2007Co-Authors: Christopher M. Spillmann, B. R. Ratna, Jawad NaciriAbstract:The macroscopic mechanical response of a freestanding, electroclinic liquid crystal elastomer to an applied electric field is described. Contraction strains and shearing were observed upon e-field application when 60-μm-thick elastomer films were tested normal and parallel to smectic layers, respectively. The anisotropic response observed in the two orthogonal directions with respect to the smectic layers correlate calculated from mechanical studies with the Induced Tilt of the molecules. The electrostrictive and electroclinic coefficients agree well with the values calculated from optical Tilt angle measurements.
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electroclinic liquid crystals with large Induced Tilt angle and small layer contraction
Physical Review E, 2000Co-Authors: Mark S Spector, Jawad Naciri, B. T. Weslowski, Paul A Heiney, David B Holt, Ranganathan ShashidharAbstract:Optical and x-ray scattering studies of a chiral, organosiloxane smectic-A liquid crystal indicate a large field Induced optical Tilt of up to 31 degrees accompanied by a very small contraction of the smectic layers. This result suggests that the molecules have a nonzero Tilt even with no applied field, and that the primary effect of the field is to induce long range order in the direction of the molecular Tilt.
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Advances in liquid crystals for gray-scale applications
electronic imaging, 1999Co-Authors: Jawad Naciri, Ranganathan Shashidhar, B. T. Weslowski, Charmaine D. Wilson, B. R. RatnaAbstract:Chiral smectic A electroclinic liquid crystalline materials are prime candidates for electrooptic applications because of their gray scale capability and fast dynamic response. The evolution of this technology greatly depends on the development of chiral smectic A materials with large Induced Tilt angles, field-independent fast switching times and a broad operating temperature range. We report in this paper the physical properties of a series of liquid crystal materials. Features of this series of materials are broad smectic A phase range and large Induced Tilt angles. Such large electroclinic coefficients make these materials good candidates of the development of silicon based reflective displays. Comparison of the electrooptic performance of the materials in SmA mesophase will be discussed.
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Demonstration of Gray Scale in Electroclinic Liquid Crystals
Liquid Crystals, 1997Co-Authors: Kerry S. Nelson, Jawad Naciri, David S. Cuttino, B. R. RatnaAbstract:Liquid crystal (LC) materials possessing the chiral smectic A phase have been designed to yield high Induced Tilt angels and low response times. The primary objective of our work is to design materials that can provide the optimum Tilt angle of 22.5 degrees for applied voltages less than 5V/micrometers , making them CMOS compatible Optical response measurement to illustrate the feasibility of obtaining 256 gray levels are presented. The gray scale capability of the material is visually demonstrated using a 1 X 64 array driven by a dc balanced circuit.
Ouyang Zhongcan - One of the best experts on this subject based on the ideXlab platform.
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compression shear Induced Tilt azimuthal orientation of amphiphilic monolayers at the air water interface a c infinity c2v transition in the flow of a two dimensional hexatic structure
Physical Review E, 2003Co-Authors: Mitsumasa Iwamoto, Atsushi Tojima, Takaaki Manaka, Ouyang ZhongcanAbstract:Compression-shear-Induced Tilt azimuthal orientation of amphiphilic monolayer in Tilting phases (L-2 and L-2(')) at the air-water interface is analyzed as dynamical equilibrium of the elastic distortion of orthogonally hexagonal structure of the molecules under compression-Induced shear flow. It is shown theoretically that the compression can induce molecular Tilts lying along and/or against the flow direction. All these Tilts makeup the initial random Tilt azimuth of the molecular tails along a uniform direction. At a threshold compression speed, it causes a C-infinity-->C-2v-symmetry transition at the air-water interface. With Maxwell displacement current and optical second-harmonic generation measurements, the above theoretical results are verified experimentally in a monolayer of 4-heptyloxy-4'-cyanobiphenyl.
Mitsumasa Iwamoto - One of the best experts on this subject based on the ideXlab platform.
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compression shear Induced Tilt azimuthal orientation of amphiphilic monolayers at the air water interface a c infinity c2v transition in the flow of a two dimensional hexatic structure
Physical Review E, 2003Co-Authors: Mitsumasa Iwamoto, Atsushi Tojima, Takaaki Manaka, Ouyang ZhongcanAbstract:Compression-shear-Induced Tilt azimuthal orientation of amphiphilic monolayer in Tilting phases (L-2 and L-2(')) at the air-water interface is analyzed as dynamical equilibrium of the elastic distortion of orthogonally hexagonal structure of the molecules under compression-Induced shear flow. It is shown theoretically that the compression can induce molecular Tilts lying along and/or against the flow direction. All these Tilts makeup the initial random Tilt azimuth of the molecular tails along a uniform direction. At a threshold compression speed, it causes a C-infinity-->C-2v-symmetry transition at the air-water interface. With Maxwell displacement current and optical second-harmonic generation measurements, the above theoretical results are verified experimentally in a monolayer of 4-heptyloxy-4'-cyanobiphenyl.
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Compression-shear-Induced Tilt azimuthal orientation of amphiphilic monolayers at the air-water interface: a C(infinity)-->C2v transition in the flow of a two-dimensional hexatic structure.
Physical Review E, 2003Co-Authors: Mitsumasa Iwamoto, Atsushi Tojima, Takaaki Manaka, Ou-yang Zhong-canAbstract:Compression-shear-Induced Tilt azimuthal orientation of amphiphilic monolayer in Tilting phases (L-2 and L-2(')) at the air-water interface is analyzed as dynamical equilibrium of the elastic distortion of orthogonally hexagonal structure of the molecules under compression-Induced shear flow. It is shown theoretically that the compression can induce molecular Tilts lying along and/or against the flow direction. All these Tilts makeup the initial random Tilt azimuth of the molecular tails along a uniform direction. At a threshold compression speed, it causes a C-infinity-->C-2v-symmetry transition at the air-water interface. With Maxwell displacement current and optical second-harmonic generation measurements, the above theoretical results are verified experimentally in a monolayer of 4-heptyloxy-4'-cyanobiphenyl.
Makhfudzah Mokhtar - One of the best experts on this subject based on the ideXlab platform.
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Measurements of stimulated-Raman-scattering-Induced Tilt in spectral-amplitude-coding optical code-division multiple-access systems
Optical Engineering, 2009Co-Authors: Zaineb Al-qazwini, Mohamad Khairuddin Abdullah, Makhfudzah MokhtarAbstract:We measure the stimulated Raman scattering (SRS)-Induced Tilt in spectral-amplitude-coding optical code-division multiple-access (SAC–OCDMA) systems as a function of system main parameters (transmission distance, power per chip, and number of users) via computer simulations. The results show that SRS-Induced Tilt significantly increases as transmission distance, power per chip, or number of users grows.
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Optical Power Limitations in Spectral-Amplitude-Coding Optical Code-Division Multiple-Access Systems Due to Stimulated Raman Scattering
2008 6th National Conference on Telecommunication Technologies and 2008 2nd Malaysia Conference on Photonics, 2008Co-Authors: Zaineb A. T. Al-qazwini, Mohamad Khairuddin Abdullah, Makhfudzah MokhtarAbstract:In this paper, the maximum power per chip to keep the stimulated Raman scattering (SRS)-Induced Tilt below a specific level in spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) is evaluated for different number of users. A number of computer simulations have been conducted for this purpose. It is shown that as number of users grows, the power per chip must be decreased to control the SRS-Induced Tilt and to keep it below acceptable levels. It is also shown that SRS-Induced Tilt can significantly limit the power per chip levels when the number of users is large. This is the first time such a study is reported for OCDMA systems.