Low molar mass liquid crystals for optical storage applications

摘要

New low molar mass room temperature glasses possessing liquid crystalline orientational order have been investigated for reversible optical storage applications. The material consists of an eutectic mixture of two /spl beta/-naphthyl ester which exhibits a calorimetrically determined glass transition at T/sub g/=35/spl deg/C and a nematic to isotropic phase transition at T/sub NI/= 140/spl deg/C. As a consequence, a nematic-like non-equilibrium state is usually frozen-in below T/sub g/, which reveals many properties of glasses in combination with the orientational order of liquid crystals. Experimentally, the well-known holographic grating technique has been used for investigation of reversible storage effects. An intensity grating resulting from interference of two cw laser beams (signal and reference) is converted into a temperature grating by weak absorption and photo-thermal heating which modulates the optical properties of the material. The resulting optical grating can be frozen in the glassy state and read out nondestructively. To achieve laser heating a small amount (1-3%) of an anthraquinone dye has been added.