Self-focusing of light beam in twisted nematic waveguide

In this work we investigate light beam propagation in twisted nematic liquid crystalline film. In the linear case (for low power of the light beam) the diffraction and walk-off of the light beam is observed. Due to the optical reorientation nonlinearity light beam is self-focusing and finally spatial solitary wave is created. The direction of light beam propagation is also changing with increasing the nonlinear effect. The samples were filled with 6CHBT nematic liquid crystals and we measured the propagation of light beam at the distance of few millimeters. Nonlinear self-focusing was observed for a light power of order of few tenths of milliwats. The experimental results are in a good agreement with theoretical predictions and numerical simulation. The proposed configuration of our cell can be applied to switching of the light beam in low power all-optical systems.