Changes in the structure of photopolymer holograms during environmental testing were studied with two techniques: (1) Scanning electron microscopy of freeze-fracture cross-sections and (2) modeling the refractive index profile. The profile was estimated using optical data: reflectivities corresponding to the fundamental spatial frequency and the second harmonic. We chose to use holograms that had not been through the normal stabilization treatments for the material, in order to study the properties of the basic structure. The changes are interpreted within the context of the void model for this photopolymer's structure.
"Structural And Optical Properties Of DMP-128 Holograms During Environmental Testing", Proc. SPIE 1051, Practical Holography III, (25 May 1989); doi: 10.1117/12.951462; https://doi.org/10.1117/12.951462