Nematicons and Their Electro-Optic Control: Light Localization and Signal Readdressing via Reorientation in Liquid Crystals

Abstract

Liquid crystals in the nematic phase exhibit substantial reorientation when the molecules are driven by electric fields of any frequencies. Exploiting such a response at optical frequencies, self-focusing supports transverse localization of light and the propagation of self-confined beams and waveguides, namely “nematicons”. Nematicons can guide other light signals and interact with inhomogeneities and other beams. Moreover, they can be effectively deviated by using the electro-optic response of the medium, leading to several strategies for voltage-controlled reconfiguration of light-induced guided-wave circuits and signal readdressing. Hereby, we outline the main features of nematicons and review the outstanding progress achieved in the last twelve years on beam self-trapping and electro-optic readdressing.

Electrical Control of Optical Liquid-Crystal-Guided Microstructures

“…On the other hand, it has to be underlined that liquid crystal devices can also switch and route signals due to the modulation of external electric fields and the interplay between the light and molecules [14], especially when the nonlinearity of NLC plays a crucial role [15]. It has been shown in several papers that a milliwatt of power of laser radiation is sufficient for observation of the self-focusing effects and formation of the soliton-type propagation of light beams due to reorientation of the NLC director under an electromagnetic field of an optical wave [16][17][18][19]. Such soliton beams, called nematicons, form a waveguide channel in NLC film that can confine and guide the light beam.…”

Pyroelectric-controlled bending of a self-trapped optical beam in a photorefractive iron doped lithium niobate crystal

“…The bright and dark solitons have been observed in photorefractive crystals 3,4 , liquid crystals 5,6 and atomic vapors 7 . The solitons which are formed in nematic liquid crystals were termed nematicons 8 .…”

Electrically controlled waveguide liquid-crystal elements

“…In recent works, light beam propagation in spatially structured nematic LCs has been considered. The possibility of refraction, reflection, and polarization separation of light beams at the interface of two LC domains has been demonstrated [9][10][11], and the feasibility of light induced waveguide propagation of laser radiation and of nematicon formation has been suggested [12][13][14].…”