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We report on spatial soliton formation and self/cross waveguiding in planar cells containing a nematic liquid crystal in the presence of an externally applied voltage. Self-confinement and cross-induced guidance are demonstrated with an Argon ion laser (514 nm) and a helium–neon probe (633 nm), respectively, over millimeter lengths and with milliwatt pump powers.

We report the observation of nonlinear photorefraction in pure aligned nematic liquid crystals in the presence of an applied dc electric field. The effect is attributed to nematic axis reorientation created by the photoinduced space-charge field in combination with the applied dc field. Strong optical nonlinearity, self-diffraction, and beam-coupling effects are observed.

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In liquid crystal cells with photoconductive poly͑N-vinlyl carbazole) polymer layers, an external dc field can be completely screened by surface charge layers that develop at the liquid crystalpolymer interface. Under spatially modulated illumination, surface charge layers can be discharged in bright areas and lead to reorientation and spatially modulated Freedericksz transition. As a result, an asymmetric energy exchange in the photorefractive two-beam coupling process can take place. We propose a model to explain the origin of reorientation and phase shift in the two-beam coupling process, based on the profile and tilt of the refractive index grating. We also show that cells with just one photoconducting layer are more efficient than a typical design with two layers.