Electrically Reconfigurable Liquid Crystalline Mirrors

Reconfigurable optical materials are critical to realizing light control in eyewear or architectural windows. Here, we report on the electrical reconfiguration of the selective reflection of cholesteric liquid crystals (LCs). The distinctive responses detailed here are enabled by the preparation of a structurally chiral polymer stabilizing network that enforces anchoring of a low-molar-mass liquid crystalline media with positive dielectric anisotropy. The pitch of the reflective optical elements is directly regulated by a dc field, resulting in red or blue reflection wavelength tuning or broadening. The use of the positive dielectric LC host in concert with optimization of the material preparation conditions allows for reorientation of the LC molecules to achieve an optically clear state (homeotropic orientation) by the application of an ac field. In this way, the selective reflection of the optical elements can be moved, widened, and turned on and off. The electro-optic characteristics of these materials are another step forward to enabling the use of these materials in optics and photonics