Compensation of Interference Fringe Distortion Due to Temperature Variation in Holographic Data Storage

Photopolymer materials are feasible for holographic recording media. However, these materials shrink owing to photopolymerization and interference fringes recorded in them distort. In addition, temperature variation causes shrinkage and expansion of these materials and thus distorts recorded interference fringes. This distortion degrades reconstructed image quality and decreases the signal-to-noise ratio of the reproduced data. We applied adaptive optics controlled by a genetic algorithm to compensate for the distortion and improved the reconstructed image quality at 25 and 30 \mbox{ \circ C} ambient temperature. Under these conditions, the signal-to-noise ratio of reproduced data was more than 4 dB. Furthermore, we evaluated the distortion due to the temperature variation by using a medium angle and the wavefront of the reference beam. We found that the distortion caused by anisotropic shrinkage is slight; consequently, an optimised wavefront at 25 \mbox{ \circ C} can compensate for the interference fringe distortion and increase the signal-to-noise ratio by adjusting only the medium angle even if a temperature variation occurs. Adaptive optics can thus be used to compensate for interference fringe distortion caused by shrinkage and expansion due to temperature variation.