Abstract

Image amplification through photorefractive two-beam coupling has been demonstrated by several investigators in the last decade.¹ In these demonstrations, high image fidelity was retained in the amplified image in the limit where the intensity of this image remained small compared with that of the pump beam from which it received energy. When this condition is violated, however, and the image and pump intensities become comparable, the gain of the amplification process becomes a nonlinear function of the image intensity, resulting in distortion and contrast reduction of the amplified output image.² This situation is encountered, however, in all power-limited applications where large fractions of incident pump energy must be transferred to the image. We thus examine this regime of image amplification with strong pump depletion and consider techniques through which the associated nonlinear image degradation may be reduced. Specifically, by analyzing the two-beam coupling process in the presence of complex wavefronts, we may determine both the form of the image wave and the experimental geometry for which the amplified fidelity is maximized. These analytic results are then compared to experimental studies of image amplification in photorefractive SBN over a broad range of experimental conditions.

© 1988 Optical Society of America