Multilayer holographic recording using a two-color-absorption photopolymer

We developed a sensitive two-color-absorption photopolymer in which holograms are recorded by simultaneous irradiation with a 660 nm interference light and a 410 nm gate light. Doped with bis(silyl)pentathiophene as a two-color-photosensitive dye and 2,2-dimethoxy-2-phenylacetophenone as a radical photopolymerization initiator; its matrix contains low-refractive index binding polymers and high-refractive index monomers. The sensitivity and diffraction efficiency of 25 mum thick layers are from 1.2 x 10(-9) to 3.7 x 10(-9) cm2/mJ and from 1% to 4%. We made a three-photopolymer-layer waveguide structure, where each photopolymer layer and high-refractive index adhesive layer serves as a core layer and is sandwiched between two low-refractive index glass substrates that serve as clad layers. Gate light propagated through the adhesive layers, reference and object beams intersected the photopolymer layers, and different diffraction patterns could be written in each layer.