Personne : Galstian, Tigran
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Galstian
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Tigran
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Université Laval. Département de physique, de génie physique et d'optique
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0000000116613117
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ncf10629873
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Publication Restreint Bifurcation analysis of optically induced dynamics in nematic liquid crystals : circular polarization at normal incidence(Optical Society of America, 2005-08-01) Brasselet, Étienne.; Galstian, Tigran; Dubé, Louis J.; Dmitry, Krimer; Kramer, LorenzWe present a detailed bifurcation analysis of the nonlinear reorientation dynamics of a homeotropically aligned nematic liquid-crystal film excited by an elliptically polarized beam at normal incidence with the intensity and the polarization state of light as the control parameters. The asymmetry arising from the elliptical polarization of the excitation lightwave is shown to affect dramatically the dynamics, and various new dynamical behaviors are reported: (i) quasi-periodic rotations for almost circular polarization; (ii) a discontinuous transition, identified as a homoclinic bifurcation, to a largely reoriented state over a large range of ellipticity values; (iii) oscillations associated with large reorientation; and (iv) optical multistability between several distinct dynamical regimes.Publication Accès libre Optically induced dynamics in nematic liquid crystals : the role of finite beam size(American Physical Society, 2004-02-10) Brasselet, Étienne.; Galstian, Tigran; Dubé, Louis J.; Doyon, BernardWe report on the influence of a finite beam size on the molecular reorientation dynamics when a nematic liquid crystal film is excited by a laser beam. We present experimental evidence of a new class of nonlinear dynamics when the excitation is a Gaussian shaped, circularly polarized laser beam at normal incidence. Various nonlinear regimes, periodic, quasiperiodic, intermittent, and possibly chaotic, are observed. A physical interpretation based on walk-off effects is proposed and its implications on current research in the field are discussedPublication Restreint Bifurcation analysis of optically induced dynamics in nematic liquid crystals : elliptical polarization at normal incidence(Optical Society of America, 2005-08-01) Krimer, Dmitry; Brasselet, Étienne.; Kramer, Lorenz; Galstian, Tigran; Dubé, Louis J.We present a detailed bifurcation analysis of the nonlinear reorientation dynamics of a homeotropically aligned nematic liquid-crystal film excited by an elliptically polarized beam at normal incidence with the intensity and the polarization state of light as the control parameters. The asymmetry arising from the elliptical polarization of the excitation lightwave is shown to affect dramatically the dynamics, and various new dynamical behaviors are reported: (i) quasi-periodic rotations for almost circular polarization; (ii) a discontinuous transition, identified as a homoclinic bifurcation, to a largely reoriented state over a large range of ellipticity values; (iii) oscillations associated with large reorientation; and (iv) optical multistability between several distinct dynamical regimes.Publication Restreint Dynamics of light induced reorientation of nematic liquid crystals in spatially confined beams(Gordon and Breach, 2010-10-18) Brasselet, Étienne.; Galstian, Tigran; Dubé, Louis J.Optically induced reorientation dynamics in a nematic liquid crystal is investigated for circularly polarized laser beams with spot sizes smaller than the sample thickness. Various dynamical regimes, such as periodic, quasi-periodic, intermittent, self-organized and possibly chaotic regimes are observed. The role finite beam size is identified and a qualitative interpretation based on the spatial walk-off of the ordinary and extraordinary beams arising from double refraction phenomenon is proposed.Publication Restreint New laser induced spatio–temporal transition in nematics(Elsevier Science, 2002-05-07) Brasselet, Étienne.; Galstian, Tigran; Dubé, Louis J.; Doyon, BernardWe report the observation of a new light-induced spatio–temporal transition in homeotropically aligned nematic liquid crystals under the action of circularly polarized light. We believe that the competition of symmetric and asymmetric excitation modes is at the origin of this abrupt transition. A theoretical model explaining the main features of the observation is proposed