Abstract
The behavior of counterpropagating self-trapped optical beam structures in nematic liquid crystals is investigated. A time-dependent model for the beam propagation and the director reorientation in a nematic liquid crystal is numerically treated in three spatial dimensions and time. We find that the stable vector solitons can only exist in a narrow threshold region of control parameters. Below this region the beams diffract, above they self-focus into a series of focal spots. Spatiotemporal instabilities are observed as the input intensity, the propagation distance, and the birefringence are increased. We demonstrate undulation, filamentation, and convective dynamical instabilities of counterpropagating beams. Qualitatively similar behavior as of the copropagating beams is observed, except that it happens at lower values of control parameters.
Highlights
Nematic liquid crystals (NLC) exhibit huge optical nonlinearities, owing to humongous refractive index anisotropy, coupled with the optically-induced collective molecular reorientation
Thanks to the optically nonlinear, saturable, nonlocal and nonresonant response, NLC have been the subject of considerable study in recent years, from both theoretical [3, 4] and experimental points of view [5,6,7,8,9,10]
In an earlier publication [11] we investigated the propagation of laser beams in NLC, both in time and in 3 spatial dimensions, using an appropriately developed theoretical model and a numerical procedure based on the split-step fast Fourier transform technique
Summary
Nematic liquid crystals (NLC) exhibit huge optical nonlinearities, owing to humongous refractive index anisotropy, coupled with the optically-induced collective molecular reorientation. They behave in a fluid-like fashion, but display a long-range order that is characteristic of crystals [1, 2]. Belic narrow region of beam intensities, similar to the case of copropagating beams, but at lower values of the control parameters This region the beams diffract, above the region the beams display periodic and even chaotic behavior. Differences between the in-phase and out-of-phase components of the dipole beam are investigated
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