Theory of second-harmonic generation in nematic liquid crystals

Ouyang, Zhen; Xie, Yan

doi:10.1103/physreva.32.1189

Cited by 34 publications

(8 citation statements)

References 26 publications

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“…Since it is generally accepted that the walls of the nanotubes are conformed by an amorphous centro-symmetric structure, formed by the aggregation of nanoparticles with sizes ranging from 2.5 to 4 nm and conformed by tetra and hexacoordinated aluminum (AlO 4 and AlO 6 polyhedral units) [51,52], no SHG is produced by the PR-AAM. Only very weak and negligible surface SHG-effects (generally detected by Lock-In amplification) may arise due to the symmetry breakdown typical of surfaces and interfaces or according to the quadrupolemoment mechanism [53,54]. This amorphous structure has been verified in our reference samples by X-ray diffraction (XRD) measurements (not shown here, [49]) where a broad XRD-spectra has been observed.…”

Section: Nlo -Measurementsmentioning

confidence: 82%

Optical Properties of Fluorinated Bent-Core Liquid Crystals Confined in Anodic Alumina Nanotubes

Morales–Saavedra

Mata-Zamora

Ontiveros-Barrera

et al. 2010

Molecular Crystals and Liquid Crystals

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In the present work, oxalic amorphous porous anodic alumina membranes with highly ordered porous arrays and average nanometric porous dimensions of 70 nm in diameter and 17 microns in depth (nanotubes) were prepared and successfully used as host matrix for fluorinated bent-core liquid crystals. Atomic force microscopy studies were performed on the organic-inorganic hybrid samples in order to explore surface morphology and optimal insertion of these liquid crystalline (LC)-compounds into this environment. The quadratic nonlinear optical (NLO) and spectroscopic properties of the implemented mesogen with the nanotube-like confinement were systematically studied in order to evaluate its optical performance. Bent core molecules have shown interesting optical properties which have not yet been intensively investigated in solid-state hybrid structures. Hence, the obtained hybrid composites represent a promising field of investigation in the route to functional bent-core based materials, where different bent-core mesomorphic structures can be obtained and are of interest for new and improved applications in nanotechnology.

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Section: Nlo -Measurementsmentioning

confidence: 82%

Optical Properties of Fluorinated Bent-Core Liquid Crystals Confined in Anodic Alumina Nanotubes

Morales–Saavedra

Mata-Zamora

Ontiveros-Barrera

et al. 2010

Molecular Crystals and Liquid Crystals

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“…Hence we discount SMHRS as a significant contributor to the nematic phase SH signal. [49] Using a description of SHG in dielectric media, incorporating intermolecular interactions, [50][51][52] collective effects [19,53] and surface interactions, [17,18] we examine the sources of the SH signal in the nematic phase. The second-order non-linear or SH polarisation P 2 ð Þ induced in such a medium by the electric field of the electromagnetic wave traversing the medium is given by [49] …”

Section: Source Of Sh Lightmentioning

confidence: 99%

“…In terms of their relative magnitudes, the second term is very weak compared to the third term in a nematic LC. [53] One of our initial assumptions is that the contribution from the surface polarisation to the SH signal, described by the fourth term, is negligible. [49] The dominant contribution to the SH signal in the nematic phase thus comes from the third term, χ $ ð3Þ E P EE.…”

Section: Source Of Sh Lightmentioning

confidence: 99%

Second-harmonic generation and the influence of flexoelectricity in the nematic phases of bent-core oxadiazoles

et al. 2016

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Second-harmonic generation (SHG) in the nematic phase of bent-core oxadiazole-based liquid crystals (LCs) was studied and compared to that for the rod-like compound 4-cyano-4ʹ-n-octylbiphenyl (8CB). Weak, isotropically scattered second-harmonic (SH) light was observed for all materials, consistent with SHG by nematic director fluctuations. The SH intensity produced by the bent-core materials was found to be up to~3.4 times that of 8CB. We discuss this result in terms of the dependence of SH intensity on temperature, elastic constants and flexoelectric coefficients. We have calculated the latter by using a molecular field approach with atomistic modelling, thus demonstrating how molecular parameters contribute to the flexoelectric coefficients and illustrating the potential of this method for predicting the flexoelectric behaviour of bent-core LCs. We show that the increased SH signal in the bent-core compounds is partly due to their nematic phases being at a much higher temperature, and also potentially due to them having greater flexoelectric coefficients, up to~1.5 times those of 8CB. These estimates are consistent with reports of increased flexoelectric coefficients in bent-core compounds in comparison to rod-like compounds.ARTICLE HISTORY

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“…For SHG in NLC, the subsidiary nonlinear polarization P (2ui) associated with curvature strain in given by [1] di y p" i (2w)= X . ..…”

Section: Nlmentioning

confidence: 99%

Symmetry Properties of Nematic Liquid Crystals with Simple Curvature Strain

Zhong-can¹,

Yu-zhang²,

YiZhuang³

1986

Commun. Theor. Phys.

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Theory of second-harmonic generation in nematic liquid crystals

Cited by 34 publications

References 26 publications

Optical Properties of Fluorinated Bent-Core Liquid Crystals Confined in Anodic Alumina Nanotubes

Optical Properties of Fluorinated Bent-Core Liquid Crystals Confined in Anodic Alumina Nanotubes

Second-harmonic generation and the influence of flexoelectricity in the nematic phases of bent-core oxadiazoles

Symmetry Properties of Nematic Liquid Crystals with Simple Curvature Strain

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