Optically induced dynamics in nematic liquid crystals: The role of finite beam size.
We 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 discussed.
Laboratoire de Photonique Quantique et Moléculaire, Ecole Normale Supérieure de Cachan, 94235 Cachan Cedex, France. ebrassel@lpqm.ens-cachan.fr
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