Angular dependence of light transmittance in polymer dispersed liquid crystals

Polymer dispersed liquid crystals (PDLC's) are composite materials made of a dispersion of liquid-crystal droplets in a polymeric matrix. The droplets appear as highly optically anisotropic spheres with random orientation. Light impinging on a film of this material is almost entirely scattered unless the application of an electric field aligns the liquid-crystal molecules inside the droplets so that all droplets behave as uniaxial media aligned to the applied field, If the polymer refractive index is equal to the ordinary refractive index of the liquid crystal the sample becomes transparent for normally impinging light. Unlike common glass, the angular dependence of light transmittance is not given by Fresnel relations hut is a fairly intricate function of the liquid-crystal distribution inside the droplets. In the framework of the general theory of PDLC's by Palffy-Muhoray and co-workers. [Mol. Cryst. Liq. Cryst. 243, 11 (1994); 179, 445 (1990)], using the anomalous diffraction approach scattering by Zumer [Phys. Rev. A 37, 4006 (1988)], we introduce a mathematical model of PI)LC transparency versus applied voltage and the incidence angle. Experimental results are presented, The experimental results correspond well ro the theoretical results