Computational modelling of light propagation in textured liquid crystals based on the finite-difference time-domain (FDTD) method

Light propagation through uniaxial rod-like nematic liquid crystal films containing singular (thin) and non-singular (thick) line disclinations is computed using the finite-difference time-domain method (FDTD), which is based on accurate numerical solutions to the governing Maxwell equations. The results obtained by the FDTD method are compared with classical matrix-type methods, including the aggregate model and Berreman's method. It is found that the optical signals for singular and non-singular defects predicted by the matrix methods deviate significantly from the FDTD method because director gradient effects on the plane normal to the incident light are not properly taken into account . It is also found that the FDTD optical signal for singular thin lines has a characteristic length scale associated with the wavelength of the incident light, while for non-singular thick lines the scale is associated with the defect escaped core dimensions. The FDTD method offers an accurate quantitative tool for use in new applications including liquid crystal-based biosensors and rheo-optical characterization of liquid crystalline polymers.