Abstract

We analyze the temporal and spatial nature of the diffracted light from a photorefractive volume hologram under the influence of electronic noise in the material. Because of this noise, the holographic grating within the crystal is not strictly periodic; in other words, it has random fluctuations in both amplitude and period. Gaussian beam illumination at the nominal Bragg angle is assumed. The reason for this choice is that we can now evaluate not only the temporal statistics in the diffracted light, but also its spatial randomness. This quantitative evaluation achieved through defining a system transfer function that relates the output diffracted light to the input in the spatial frequency domain. For light nominally incident at the Bragg angle, this transfer function may be derived by Fourier transforming the paraxial wave equation in the presence of interaction terms. Estimation of spatial randomness is not possible to calculate assuming plane wave illumination since one cannot monitor transverse fluctuations along its wavefront. By using first- order approximation, the temporal and spatial noise ratios are obtained. Their dependence on reading time, reading beam intensity, grating spacing, and temperature are predicted.

© 1991 Optical Society of America