Thermal orientation effect in a nematic liquid crystal

Trashkeev, S. I.; Бритвин, А. В.

doi:10.1134/s1063784211060247

Cited by 12 publications

(14 citation statements)

References 4 publications

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“…A theoretical model was proposed for explanation. This model reveals existence of NLC's orientation thermoelasticity governed by quadratic dependence on the temperature gradient [9]. The detected thermal orientation effect (unavoidable in the presence of radiation absorption) along with the well-known light-induced Fredericks effect [2] cause the central symmetry breakdown and formation of disclinations.…”

Section: Thermal Orientation Effect In Nlcsmentioning

confidence: 81%

“…As seen in figure 10, the self-confined beam in the NLC orientation structure has regular transversal dashes. This filamentation-like effect can be caused by combination of the thermal orientation effect due to absorption [4,9] and the nonlinear orientation self-focusing due to light-induced Fredericks effect [2]. The radial structures (figure 11) appeared when a heat-spreading mirror-like plate was used in the above experimental arrangement instead of the bottom glass plate.…”

Section: Laser Frequency Conversion In Nlcsmentioning

confidence: 99%

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New methods of highly efficient controlled generation of radiation by liquid crystal nanostructures in a wide spectral range

Bagayev¹,

Klementyev²,

Nyushkov³

et al. 2012

J. Phys.: Conf. Ser.

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Abstract. We report the recent results of research focused on a new kind of soft matter -the liquid-crystal nanocomposites with controllable mechanical and nonlinear optical properties. These are promising media for implementation of ultra-compact photonic devices and efficient sources of coherent radiation in a wide spectral range. We overview the technology of preparation of nematic-liquid-crystal media saturated with disclination defects. The defects were formed in different ways: by embedding nanoparticles and molecular objects, by exposure to alpha-particle flux. The defect locations were controlled by applying an electric field. We also present and discuss the recently discovered features of nematic-liquid-crystal media: a thermal orientation effect leading to the fifth-order optical nonlinearity, enormous second-order susceptibility revealed by measurements, and structural changes upon exposure to laser radiation. We report on efficient generation of harmonics, sum and difference optical frequencies in nematic-liquid-crystal media. In addition, transformation of laser radiation spectra to spectral supercontinua, and filamentation of laser beams were also observed in nematic-liquid-crystal media. We conclude that most nonlinear optical effects result from changes of the orientational order in the examined nematic liquid crystals. These changes lead to the symmetry breaking and disclination appearances.

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Section: Thermal Orientation Effect In Nlcsmentioning

confidence: 81%

Section: Laser Frequency Conversion In Nlcsmentioning

confidence: 99%

New methods of highly efficient controlled generation of radiation by liquid crystal nanostructures in a wide spectral range

Bagayev¹,

Klementyev²,

Nyushkov³

et al. 2012

J. Phys.: Conf. Ser.

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show abstract

“…Since the thermal conductivity of a nematic is anisotropic, thermal gradients may cause a realignment of the optical axis. [40][41][42] For a homeotropic sample, this would correspond to a tilting of the director away from the cell normal. In a typical hot stage, a temperature variation across the sample plane is unavoidable because of the presence of the transparent window necessary for optical observations.…”

Section: Results: Optical Conoscopy Fcpm and Carsmentioning

confidence: 99%

Search for biaxiality in a shape-persistent bent-core nematic liquid crystal

et al. 2012

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“…The direction of optical axis in NLCs is related to the director, which is defined as the vector of preferred orientation of the long axes of NLC molecules and depends on many external and internal factors. The orientation of NLC molecules is determined by applied electrostatic and light fields (the Freedericksz effect [2]), heat flows (thermal orientation effects [16]), the shape of the volume occupied by the NLC and the boundary conditions on the surface [6], and the internal disclinations [3]. All these factors may lead to complex NLC anisotropy, inhomogeneous in space and time.…”

Section: Resultsmentioning

confidence: 99%

Generation of harmonics and supercontinuum in nematic liquid crystals

et al. 2013

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Nonlinear optical properties of nematic liquid crystals (NLC) have been investigated. A technique for efficient laser frequency conversion in a microscopic NLC volume deposited on an optical fibre end face is experimentally demonstrated. An efficient design of a compact NLC-based IR frequency converter with a fibre input and achromatic collimator is proposed and implemented. Simultaneous generation of the second and third harmonics is obtained for the first time under pumping NLC by a 1.56-mm femtosecond fibre laser. The second-harmonic generation efficiency is measured to be about 1 %, while the efficiency of third-harmonic generation is several tenths of percent. A strong polarisation dependence of the third-harmonic generation efficiency is revealed. When pumping NLC by a cw laser, generation of spectral supercontinua (covering the visible and near-IR spectral ranges) is observed. The nonlinear effects revealed can be due to the light-induced change in the orientational order in liquid crystals, which breaks the initial symmetry and leads to formation of disclination structures. The NLC optical nonlinearity is believed to be of mixed orientationalelectronic nature as a whole.

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Thermal orientation effect in a nematic liquid crystal

Cited by 12 publications

References 4 publications

New methods of highly efficient controlled generation of radiation by liquid crystal nanostructures in a wide spectral range

New methods of highly efficient controlled generation of radiation by liquid crystal nanostructures in a wide spectral range

Search for biaxiality in a shape-persistent bent-core nematic liquid crystal

Generation of harmonics and supercontinuum in nematic liquid crystals

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