Holographic 'development' of a hidden UV image recorded on a liquid crystalline polymer

Films of a chiral liquid crystalline side chain polymer with azobenzene chr omophores are shown to be a novel medium for UV image recording. The princi ple includes a primary process of recording a UV image (e.g, of a mask) by unpolarized UV light excitation of a considerable amount of extraordinary l ong living cis-isomers of the azo-chromophores. After that the image is 'hi dden' because it is not seen under a polarising microscope equipped with a red filter. At the second stage, the image is developed by a linearly polar ized beam of visible (blue or green) light that converts cis-isomers back i nto their trans-counterparts. The image appears in the form of the spatial modulation of the optical anisotropy which is measured at each stage in sit u by an ellipsometry technique. The development of the hidden images has be en done both with a uniform illumination and a holographic technique using a grating formed by interfering beams of visible Ar-laser light. Recorded i mages are erased by the second, this time uniform, UV irradiation of the fi lm and the process may be repeated many times on the same spot. (C) 2000 El sevier Science B.V. All rights reserved.