共查询到20条相似文献,搜索用时 15 毫秒
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We investigate, for the first time to our knowledge, the discrete propagation of near-infrared light in a voltage-controlled array of channel waveguides in undoped nematic liquid crystals under planar anchoring conditions. This novel geometry enables us to drive the system from one-dimensional bulk diffraction to discrete propagation and, for larger excitations, to discrete spatial solitons, or nematicons. The observed phenomena are adequately described by a scalar model that encompasses the voltage-dependent reorientational response of the material. 相似文献
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在数值和实验上研究了向列相液晶中空间光孤子的相互作用.向列相液晶中的响应函数为指数衰减函数,这不同于Snyder-Mitchell模型.数值模拟发现向列相液晶中的孤子相互作用仍然满足交叉点位置与输入功率的平方根成反比,强非局域下的Snyder-Mitchell模型交叉点位置与两束光的间距无关,而在向列相液晶中交叉点位置与两束光的间距有关;在实验上发现,向列相液晶中两束光交叉点的位置与输入功率平方根成反比,还和形成孤子的临界功率以及两束光之间的间距有关. 相似文献
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在数值和实验上研究了向列相液晶中空间光孤子的相互作用.向列相液晶中的响应函数为指数衰减函数,这不同于Snyder-Mitchell模型.数值模拟发现向列相液晶中的孤子相互作用仍然满足交叉点位置与输入功率的平方根成反比,强非局域下的Snyder-Mitchell模型交叉点位置与两束光的间距无关,而在向列相液晶中交叉点位置与两束光的间距有关;在实验上发现,向列相液晶中两束光交叉点的位置与输入功率平方根成反比,还和形成孤子的临界功率以及两束光之间的间距有关.
关键词:
强非局域非线性
向列相液晶
孤子相互作用
交叉点 相似文献
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Alberucci A Peccianti M Assanto G Coschignano G De Luca A Umeton C 《Optics letters》2005,30(11):1381-1383
We demonstrate that, in suitably designed cells with undoped nematic liquid crystals, extraordinary-wave spatial solitons can be excited at every applied voltage without adjustments in the input polarization. Their walk-off, hence direction of propagation, is externally controlled over angles as large as 7 degrees. The results pave the way not only to polarization-forgiving generation but also to voltage readdressing of these extraordinary-wave nematicons. 相似文献
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Nonlocal spatial soliton interactions in nematic liquid crystals 总被引:17,自引:0,他引:17
The interaction between spatial optical solitons in undoped nematic liquid crystals is governed by reorientational nonlinearity with a significant nonlocality. We demonstrate several cases of interactions, including crossing, interlacing, and merging of spatial solitons in voltage-biased liquid-crystal cells. A scalar model accounts for the main features that were experimentally observed. 相似文献
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(2+1) -dimensional spatial solitary waves are generated by launching of milliwatt-power linearly polarized light beams in voltage-biased planar cells with undoped nematic liquid crystals, regardless of the degree of spatial coherence of the input. Coherent and incoherent self-trapping, as well as guidance of a weaker copolarized signal, is demonstrated. 相似文献
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In this work we demonstrate the properties of spatial solitary waves in chiral nematic liquid crystals with an external electric field. Such self-trapped beams, called nematicons, were created due to the optical reorientation nonlinearity for a light power of a few tens of milliwatts. We show that the direction of propagation of such nematicons can be changed by applying an external electric field. Additionally, this effect can be modified by changing the input polarization of the light beam. The experimental results were obtained in four independent guiding layers created by a chiral nematic structure. 相似文献
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E. Magyari 《Zeitschrift für Physik B Condensed Matter》1984,56(1):1-3
The existence of a localized relaxation mode of the recently observed solitarylike director waves in nematic liquid crystals is pointed out. This mode describes a nearly instantaneous regression of the perturbed director wave to its initial profile.Work supported by the Swiss National Science Foundation 相似文献
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The paper reports new nematic liquid crystals that are paramagnetic. 相似文献
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We demonstrate the first fully controlled generation of immobile and slow spatial gap solitons in nonlinear periodic systems with band-gap spectra, and observe the key features of gap solitons that distinguish them from discrete solitons, including a dynamical transformation of gap solitons due to nonlinear interband coupling. We also describe theoretically and confirm experimentally the effect of the anomalous steering of gap solitons in optically induced photonic lattices. 相似文献
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A. Humpert A.J. Masters M.P. Allen 《The European physical journal. Special topics》2016,225(8-9):1723-1732
We examine the behaviour of single-particle orientational time correlation functions in nematic liquid crystals. As well as the expected dynamics involving oscillation in a mean-field potential, and occasional jumps between orientations parallel and antiparallel to the director, we provide the first simulation evidence of long-time tails characteristic of coupling to director fluctuations. 相似文献
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Thermomechanical mechanism of the director reorientation in twisted nematic liquid crystals caused by the one-dimensional longitudinal temperature gradient is predicted and studied theoretically. The calculated director reorientations are in the range that can be measured experimentally very easily. 相似文献
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S. Marčelja 《Solid State Communications》1973,13(7):759-762
The ordering of hydrocarbon end-chains in nematic liquid crystals has been calculated by numerical summation over all chain configurations in the molecular field. The results, used in a self-consistent calculation of the orientational ordering for the full system, explain the variation of the isotropic-nematic transition temperatures (including the even-odd effect) and transition entropies with end-chain length. 相似文献
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Thermotropic biaxial nematic liquid crystals 总被引:1,自引:0,他引:1
We have synthesized liquid crystal (LC) mesogens based on a nonlinear oxadiazole unit that exhibit nematic phases near 200 degrees C. Polarized microscopy and conoscopy indicate that these LCs are biaxial nematics. Unambiguous and quantitative evidence for biaxiality is achieved using 2H NMR spectroscopy. "2D powder" spectra, obtained by rotating 2H-labeled samples about an axis perpendicular to the magnetic field at approximately 200 Hz, yield phase biaxiality parameters of approximately 0.1 when coupled with rigorous and proven simulations. 相似文献
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Different modes of bistable switching in liquid crystals with frequency inversion of the dielectric anisotropy sign are discussed.
The study is performed by numerical simulation and experimentally. It is shown that dual frequency driving can be effectively
used to control switching between topologically equivalent and non-equivalent director field distributions. The experimental
results on temperature performance of the dual-frequency switching and possible driving methods for energy consumption and
expanding the temperature range are presented. 相似文献
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S. Krishna prasad Geetha G. Nair Gurumurthy Hegde K. L. Sandhya D. S. Shankar Rao Chethan V. Lobo 《Phase Transitions》2013,86(6):443-455
Temperature, concentration of the solvent and pressure are the parameters that are well known to bring about phase transitions in liquid-crystalline systems. In recent years a new parameter has been added to this list: light. The principle behind these photoinduced transitions is the light-driven shape transformation of certain photoactive materials like, e.g., azobenzene. In this article, we present results of various aspects of our recent investigations on such photoinduced transitions in the nematic phase and highlight the feature that light is a new tool to study phase transitions and the associated critical phenomena. 相似文献