Electrically Switchable Bragg Gratings from Liquid Crystal/Polymer Composites

T he use of holographic materials is increasing at a dramatic rate in research and consumeruse systems. A recent report estimated that the worldwide holographic market for 1998 was as high as $2.8 billion.1 While static holograms are by far the most widely used, many applications would bene® t greatly by being able to turn the holograms off and on like an optical switch. This article describes the development of holographically recorded liquid crystal/polymer composites known as holographic polymer-dispersed liquid cr ystals (HPDLCs). H-PDLCs are prepared by causing inter ference between two coherent laser beams in a photosensitive monomer/liquid crystal (LC) mixture contained between two sub-