Surface relief model for photopolymers without cover plating

Abstract

Relief surface changes provide interesting possibilities for storing diffractive optical elements on photopolymers and are an important source of information to characterize and understand the material behaviour. In this paper we present a 3-dimensional model based on direct measurements of parameters to predict the relief structures generated on the material. This model is successfully applied to different photopolymers with different values of monomer diffusion. The importance of monomer diffusion in depth is also discussed.

Polymerizable Materials for Diffractive Optical Elements Recording

“…τ can be calculated by fitting the phase depth of the grating variation with time [6]. To obtain this value, we can use Fick's Law equation to describe species concentration after exposure and the fitting of the temporal variation for ∆φ: 8) where the species modulation generated inside the photopolymer is represented by ∆φ…”

“…Along with the evolution of photonics, communications and optical processing of information, the relevance, and capabilities of these materials to store any kind of phase or amplitude diffraction pattern, with good results also for low spatial frequencies, are surfacing [4][5][6]. At this point, the complete characterization of these materials for low spatial frequencies is decisive to design a material with the optimum characteristics for each specific application [7,8].…”

Relief diffracted elements recorded on absorbent photopolymers

“…The experimental set-up is presented in Fig. 1 and is similar to the one used in ref [16]. to measure the phase-shift as a function of exposure energy.…”

“…In this sense, classically, PVA materials are prepared with acrylamide as the main monomer, and this compound has an important drawback -it is carcinogenic [13]. Therefore, we substituted acrylamide by sodium acrylate with good results [14][15][16]. In this paper we study both materials.…”

“…Therefore we decided to analyze separately the two phenomena measurable in PVA materials without coverplate, the relief structures formed on the free material surface and the variation in the refractive optical index due to monomer polymerization. Once we have determined the parameters involved on the diffractive phase image formation, we proposed a model (Appendix I) to predict the surface variations in PVA materials using different monomers with different values of polymerization rates and diffusions velocities [16]. We demonstrated the utility of this model for exposures shorter than 30 seconds, and the in-dark evolution (post-evolution in absence of recording light) due to monomer diffusion [16].…”