Switching and intrinsic position bistability of soliton beams in chiral nematic liquid crystals

Abstract

We study theoretically and experimentally the propagation of light beams in chiral nematic liquid crystals. Despite the rather complex refractive index distribution of these crystals, their reorientational nonlinearity can compensate for diffraction, leading to robust solitonlike beams propagating along helical trajectories. We demonstrate that, due to a symmetry-breaking instability of the liquid crystal structure, these beams undergo abrupt switching and bistability, features that are of potential interest for applications to all-optical signal processing.

Nematicon-enhanced spontaneous symmetry breaking

“…Thus, a hysteresis cycle controlled by the incidence angle was observed, in analogy to the position memory reported in Ref. [18] with reference to chiral NLC. All the acquired states were stable in time.…”

“…The local slope of the path follows the walk-off dependence on reorientation [14,17]: with reference to the section just after the input, the slope increased up to P=70 mW (=45 degrees), then started to diminish for further increases in power. The memory of the previous state should allow for the observation of hysteresis when the incidence angle is varied at a fixed input power, the latter above FT for normal incidence [18][19]. We launched an input beam tilted by about 4° with respect to the axis z.…”

Self‐assembly and antistatic property of ionic liquid crystalline polymers

“…All this facts could be attributed by the alignment effect induced by the electric field on the mesophase in the smectic phase. As shown in Figure 9, the mesogens are aligned with response to an applied electric field, that is, the electric field can induce the reorientation of the orienting axis 44 . Therefore, some convenient ion channels could be formed in the regular arrangement interstitial layer of smectic phase induced by electric field.…”

Soliton enhancement of spontaneous symmetry breaking

“…Since e-wave nonlinear beams propagate in a system with broken symmetry according to their previous evolution (selfconfinement and refraction), such memory effect can be expected to lead to hysteresis and bistability [33,37]. To this extent we explored beam dynamics for powers above OFT as the incidence angle was continuously varied along a close loop.…”