Strong self-focusing in nematic liquid crystals

Braun, Erez; Faucheux, Luc P.; Libchaber, Albert

doi:10.1103/physreva.48.611

Cited by 124 publications

(56 citation statements)

References 21 publications

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“…All-optical reorientation enables nematicon generation even at sub-mW power levels [23][24], but such self-trapped beams are usually subject to dynamic instabilities due to the interplay between optical torque, thermal agitation, fluid convection [25], anisotropy [26], and anchoring conditions at the boundaries.…”

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confidence: 99%

Quenching nematicon fluctuations via photo-stabilization

Assanto

Karimi

Alberucci

et al. 2016

Photon. Lett. Poland

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Abstract-Light localization into optical spatial solitons can be achieved by launching optical beams in nonlocal nonlinear nematic liquid crystals. Such solitons often undergo undesired fluctuations of their trajectories. We demonstrate that partial polymerization in monoacrylate-doped nematic liquid crystals is effective in quenching such fluctuations in transverse space.Spatial nonlocality in the optical response of dielectrics entails a number of benefits when dealing with nonlinear optics for signal processing and switching. It was recognized in the early days of nonlinear integrated optics that a diffusive hence nonlocal response, such as in thermo-optic materials, could lead to longitudinal optical feedback even in the absence of resonances, with consequent hysteresis versus input beam excitation [1][2][3][4]. More recently, a nonlocal nonlinear response was found fit to stabilize beam self-confinement into twodimensional (2D) spatial solitons which, in local Kerr media with an intensity-dependent refractive index, are otherwise unstable and prone to filamentation and catastrophic collapse [5][6][7][8][9][10]. In the highly nonlocal limit in space, spatial optical solitons tend to mutually attract and exhibit long-range interactions, [11][12] as well as reduced modulational instability [13][14], incoherent character [15][16], and breathing oscillations [17][18]. The synergy of local and nonlocal effects in time was indicated as a route towards spatiotemporal light bullets [19].Nematic liquid crystals (NLC) are molecular liquids with a substantial degree of orientational order, so much so that they exhibit a macroscopically (positive) uniaxial response, a reorientational nonlinearity, a large electrooptic effect as well as high nonlocality [20][21]. When an intense light beam with electric field E wave propagates through NLC, the induced microscopic dipoles tend to rotate under the action of torque:with  0 the dielectric susceptibility of vacuum, n e and n o the refractive index eigenvalues for electric fields parallel and orthogonal to the optic axis n, respectively. The resulting increase of the orientation angle  between the wavevector k||z and n yields self-focusing through an increase in the extraordinary (e)-refractive index ruled by   When self-focusing compensates for diffraction, a stable spatial soliton (a nematicon) is formed, with an associated graded-index waveguide wider that the beam generating it [5,22]. All-optical reorientation enables nematicon generation even at sub-mW power levels [23][24], but such self-trapped beams are usually subject to dynamic instabilities due to the interplay between optical torque, thermal agitation, fluid convection [25], anisotropy [26], and anchoring conditions at the boundaries.Transverse light localization through all-optical reorientation, in fact, is understood to locally increase the order parameter of this soft matter; this local field (alloptical) effect combines/competes with the bulk reorientation of the optic axis (molecular director) due to ela...

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confidence: 99%

Quenching nematicon fluctuations via photo-stabilization

Assanto

Karimi

Alberucci

et al. 2016

Photon. Lett. Poland

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“…Most of the theoretical and experimental works were done for thin samples and only a few papers reported propagation of light beam at lengths longer than the Rayleigh distance. There were experiments showing the self-focusing due to the reorientation process inside liquid crystals in capillaries [4][5][6][7], in planar cells [8], and in planar waveguides [9]. In this article, the main idea leading to create optical solitons due to the reorientation nonlinearity in liquid crystals is presented.…”

Section: Introductionmentioning

confidence: 99%

Spatial Solitons in Liquid Crystals

Karpierz

2001

Soliton-Driven Photonics

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Reorientational phenomenon in liquid crystals is unique for nonlinear optics applications. Recently there have been shown that the reorientational nonlinearity in nematic liquid crystals can govern spatial solitons in both waveguide and bulk geometry. Such solitons require a few milliwats of light power and they can be controlled by the state of light polarisation or an external electric field. In this paper, the theoretical analysis and experimental results on optical solitons in nematic liquid crystals due to the reorientational nonlinearity are reviewed. The discussion of their properties is preceded by a brief introduction to nonlinear optics of liquid crystals.

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“…Passing continuous laser beams through nematic LCs reveals the existence of static spatial patterns in cylindrical [10] and planar [11] geometries. The basic physical mechanism which support these time-independent patterns is the balance between the nonlinear refraction (self-focussing) and spatial diffraction in the nematic.…”

Section: Introductionmentioning

confidence: 99%

Standard and embedded solitons in nematic optical fibers

et al. 2003

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A model for a non-Kerr cylindrical nematic fiber is presented. We use the multiple scales method to show the possibility of constructing different kinds of wavepackets of transverse magnetic (T M ) modes propagating through the fiber. This procedure allows us to generate different hierarchies of nonlinear partial differential equations (P DEs) which describe the propagation of optical pulses along the fiber. We go beyond the usual weakly nonlinear limit of a Kerr medium and derive a complex modified Korteweg-de Vries equation (cmKdV) which governs the dynamics for the amplitude of the wavepacket. In this derivation the dispersion, self-focussing and diffraction in the nematic are taken * Fellow of SNI, Mexico † Correspondence author. E-mail: zepeda@fisica.unam.mx ‡ Fellow of SNI, Mexico 1 into account. It is shown that this cmKdV equation has two-parameter families of bright and dark complex solitons. We show analytically that under certain conditions, the bright solitons are actually double embedded solitons. We explain why these solitons do not radiate at all, even though their wavenumbers are contained in the linear spectrum of the system. We study (numerically and analytically) the stability of these solitons. Our results show that these embedded solitons are stable solutions, which is an interesting property since in most systems the embedded solitons are weakly unstable solutions. Finally, we close the paper by making comments on the advantages as well as the limitations of our approach, and on further generalizations of the model and method presented.

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Strong self-focusing in nematic liquid crystals

Cited by 124 publications

References 21 publications

Quenching nematicon fluctuations via photo-stabilization

Quenching nematicon fluctuations via photo-stabilization

Spatial Solitons in Liquid Crystals

Standard and embedded solitons in nematic optical fibers

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