Absorption effects in photorefractive volume-holographic memory systems II Material heating

We consider how absorption-induced material heating alters the phase profile, the scale, the orientation, and the Bragg matching of volume holograms. We derive theoretical equations that consider the prisming, the lensing, and the Bragg mismatching that occur during material heating and compare these with experimental observations. From our Bragg-mismatching considerations we show how both read beam angle and wavelength need to be dithered for proper compensation of volume holograms for material-heating effects. Our results indicate that material heating in volume-holographic memory systems poses a severe threat to system performance. This threat is shown to be very significant in Fourier plane holograms but only moderately significant in image plane holograms.