Liquid crystals possess many unique physical, optical, and electro-optical and nonlinear optical properties. In particular, nematic liquid crystals (NLC) are characterized by large birefringence that spans a broad spectral range, and large susceptibility to ac, dc, and optical fields. Researchers at the Pennsylvania State University recently discovered a nonlinear electro-optical effect in dye- or fullerene C60-doped NLC films. They have demonstrated, by theory and experiments, the possibility of using low power lasers of a few milliwatts, in conjunction with a small dc field to induce persistent realignment of the liquid crystal director axis (the equivalence of the c-axis or symmetry axis of a birefringent crystal), and therefore a "stored" refractive index change in these films.
by I. C. Khoo, Pennsylvania State University, University Park, Pa.