Analysis of PVA/AA based photopolymers at the zero spatial frequency limit using interferometric methods

Abstract

One of the problems associated with photopolymers as optical recording media is the thickness variation during the recording process. Different values of shrinkages or swelling are reported in the literature for photopolymers. Furthermore, these variations depend on the spatial frequencies of the gratings stored in the materials. Thickness variations can be measured using different methods: studying the deviation from the Bragg's angle for nonslanted gratings, using MicroXAM S/N 8038 interferometer, or by the thermomechanical analysis experiments. In a previous paper, we began the characterization of the properties of a polyvinyl alcohol/acrylamide based photopolymer at the lowest end of recorded spatial frequencies. In this work, we continue analyzing the thickness variations of these materials using a reflection interferometer. With this technique we are able to obtain the variations of the layers refractive index and, therefore, a direct estimation of the polymer refractive index.

In dark analysis of PVA/AA materials at very low spatial frequencies: phase modulation evolution and diffusion estimation

“…In order to eliminate the secondary reflection we introduce a black PVC adhesive on the second glass surface. As we already noted in previous papers [12], phase modulation is higher than 20π for long exposures. At this point of our analysis, we must take into account that our technique based on measuring the diffraction efficiencies of the different diffraction orders presents some difficulties for high values of phase depth [9].…”

“…The photopolymers used to store the gratings are similar to the ones used in previous works [10][11][12]. In this sense the material preparation is similar to the one presented in the previous work [9].…”

“…The method to store gratings is based on a dynamic experimental set up where a spatial phase modulator (SLM) is working in amplitude only configuration [10], determines the spatial frequency. This work is based on previous works where we analyzed the lowest spatial frequency [11,12], the zero spatial frequency limit, and some low spatial frequencies [13].…”

Investigation of the sensitivity to humidity of an acrylamide-based photopolymer containing N-phenylglycine as a photoinitiator

“…Photopolymer materials can be used in holographic data storage [1][2][3][4][5][6][7], diffractive and refractive optical elements [8,9], solar concentrators [10,11], holographic interferometry [12][13][14][15][16] and holographic sensors [17][18][19]. Acrylamide-based photopolymers are widely covered in the literature.…”

Surface relief model for photopolymers without cover plating

“…Shrinkage caused by polymerization is greatly reduced after exposure, due to monomer diffusion from the non-exposed to exposed zones [18][19][20]. In some cases this process produces swelling of the polymerized regions and the diffraction efficiency of the zero order rises to a maximum again [16].…”