The investigation of the effect of recording conditions on grating formation in a novel holographic photopolymer

Abstract

Holographic photopolymers become promising materials for future production of holographic devices. And the mechanism of hologram formation in photopolymers has been broadly studied. In this paper we present a simplified model in order to describe the monomer diffusion and photopolymerization. According to this model, the main effect the modulation of refraction index comes from the intensity of recording beams and fringe spacing during recording. So we quantitatively analyzed the effect of recording intensity and fringe spacing on diffraction efficiency, and carried out validating experiments with a novel blue-green sensitized photopolymer. Holographic gratings were recorded with different recording beam intensities and different fringe spacing respectively, and corresponding diffraction efficiency were obtained. By fitting the experimental results to the model, we obtained the material parameters, such as diffusion time constant, polymerization coefficient. The experimental results indicated that a higher recording intensity resulted in a faster growth of grating and lower saturated diffraction efficiency. And saturated diffraction efficiency increased with the increasing of fringe spacing. These agreed well with theoretical expectation. This study improves the understanding of recording process and consequently allows building more accurate holographic components in the photopolymers.