Poly(vinyl alcohol-acrylamide) photopolymers are materials of interest in the field of digital information storage (holographic memories). We analyzed the behavior of a 1-mm-thick photopolymer. Using a standard holographic setup, we recorded unslanted diffraction gratings. The material has high angular selectivity (0.4°), good sensitivity (88 mJ/cm2), and small losses caused by absorption and scattering of light. It also has a high maximum diffraction efficiency (70%). A significant induction period was seen in the material. The authors hypothesize that, during most of this induction period, polymerization does in fact take place but is not reflected in the appearance of the diffracted light until a certain threshold value of exposure is reached.
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