Latent-imaging photopolymer systems

A new high-resolution latent-imaging photopolymer system is reported for recording thick refractive-index patterns such as volume phase holograms and grating devices. A photosensitive polymerization initiator is chemisorbed on the surfaces of a porous glass matrix (average pore diameter 4 nm). The latent image is recorded by exposing the sensitized glass such that the initiator is selectively destroyed in the desired pattern. During this step, there are only small changes in the optical properties of the material, thus preventing interactions between the image being written and the optical fields writing it. The image is then developed by filling the matrix with a suitable monomer mixture and using a uniform optical exposure to initiate polymerization. During the development step, the spatially modulated initiator concentration, which constitutes the latent image, leads to a corresponding modulation of the refractive index of the polymer, and increases in the amplitude of the image of as much as a factor of 50 (Deltan up to 3 x 10(-4)) have been observed.