Process optimization for the manufacturing of holographic elements using Darol photopolymer

In the present study, dry Darol® films are thermally processed to determine the optimized conditions to achieve a large modulation of the refractive index together with good optical properties of the hologram (i.e. transparency), flatness and homogeneity. For each condition, volume phase gratings are written and characterized in terms of diffraction efficiency. A threshold temperature of 150 °C is found, and only latent holograms are obtained at lower temperature, as confirmed by thermal characterizations. Moreover, a dependence of the refractive index modulation on the line density and laser intensity is highlighted.