Photopolymers for application in holography have the advantage over silver halide emulsions that a phase hologram is formed in situ during exposure. The article describes the results of tests concerning the resolving power and photosensitivity of a combination of the monomers acryl amide and methylene-bis-acryl amide. This combination forms a copolymer under the influence of red light, when methylene blue is used as a sensibiliser. In spite of their low sensitivity, photopolymers in some instances appear to be promising substitutes for the conventional silver halide materials.
A drawback of silver halide emulsions in holographic processes is the need to use photographic developing processes, so that it takes a fair amount of time for the hologram to be completely finished. It will take longer if the hologram is also bleached to produce a phase hologram, to achieve greater diffraction efficiency. 1 It is by no means rare for the various stages of processing of the photographic plate from exposure to the end of accelerated drying (alcohol bath, hot air current) to take a total of thirty minutes.
Even if a reversing process is applied, in which the developed silver is dissolved, thus directly producing a phase hologram, the complete process may require fifteen minutes.
There are two other processes, however, which do not have the above-mentioned drawback: those employing thermoplastics 2'3 and photopolymers 4.