Recording Performance of Holographic Diffraction Gratings in Dry Films Containing Hyperbranched Polyisophthalesters as Polymeric Binders

By use of a photopolymerization-diffusion model, the diffraction efficiency of photopolymerizable recording dry films prepared from hyperbranched polyisophthalesters as polymeric binders was investigated. The recording characteristics of these films, i.e., spatial frequency, polymeric binder structure, exposure intensity, and modulation depth, are discussed in detail. For a given total exposure dose the diffraction efficiency first increases and then decreases with increasing exposure intensity, and this effect becomes more remarkable as the unsaturated concentration of polymeric binder increases. An optimum total exposure dose of 36 mJ cm^-2 and an exposure intensity of 0.4 mW cm^-2 were determined. A modulation depth of 1 was found to produce the highest diffraction efficiency. Longer-lasting gratings could be obtained by use of polymeric binders with higher cross-linking densities.