Escaping solitons from a trapping potential.

Solitons propagating within a confining potential undergo momentum-dependent scattering and eventually escape for large excitations. We experimentally highlight this phenomenon in the presence of a nonperturbative nonlinear response using self-confined light beams in a reorientational medium.

Line defects and temperature effects in liquid crystal tunable planar Bragg gratings.

Liquid crystal tunable planar Bragg Gratings produced by Direct UV Writing are capable of wavelength tuning of over 100GHz. However, such devices exhibit non-linear tuning curves with threshold points and hysteresis. We show that these effects are due to the formation of disclination structures in the liquid crystal and discuss the role of electrode defects and sample temperature on wavelength tuning.

Demonstration of 100 GHz electrically tunable liquid-crystal Bragg gratings for application in dynamic optical networks.

We demonstrate liquid-crystal-based integrated optical devices with >140 GHz electrical tuning for potential applications in dynamic optical networks. Bragg wavelength tuning covering five 25 GHz wavelength-division multiplexing channel spacing has been achieved with 170 V (peak-to-peak) sinusoidal voltages applied across electropatterned indium tin oxide-covered glass electrodes placed 60 microm apart. This tunability range was limited only by the initial grating strength and supply voltage level.

Nonspecular total internal reflection of spatial solitons at the interface between highly birefringent media.

We investigate total internal reflection of nonlocal spatial optical solitons at the interface between two differently oriented regions of a highly birefringent nematic liquid crystal. The solitons survive the interaction with an induced index mismatch and undergo nonspecular reflection, with an emerging angle differing appreciably from the incidence angle.

Nonlinear shift of spatial solitons at a graded dielectric interface.

We investigate total internal reflection of optical spatial solitons at the interface between two regions of nematic liquid crystals with different optical densities. Due to nonlinear molecular reorientation, the solitons experience a penetration depth, hence, a lateral shift that depends on the excitation, with lateral shifts from 0.7 to 1.

Two-color vector solitons in nonlocal media.

We investigate the interaction between two beams differing in wavelength and the properties of dual-frequency spatial solitons in nonlocal birefringent reorientational media. We report the first experimental observations of anisotropic nonlocal vector solitons in unbiased nematic liquid crystals. Model and simulations, based on the paraxiality along the Poynting vectors, include joint walk-off and breathing.

Control of topological defects in microstructured liquid crystal cells.

We study how the propagation of light inside recently developed micro-structured cells, can be actively tuned by polarising the nanoscale defects in the nematic liquid crystals they contain. Our 'planar-spherical' cells are formed by assembling a planar and a gold-coated hemispherical micro-mirror. Optical reflection images of the back-reflected polarised light show a remarkable change of symmetry as a function of the voltage applied to the cell.