Color cross talk in photorefractive LiNbO3

Abstract

Photorefractive LiNbO3 is an attractive material for the recording of real-time volume holograms for optical signal processing. Its ability to maintain holographic gratings for extended periods, coupled with the relative simplicity that it allows in system construction, have lead to its widespread use in electro-optic devices. Angular and wavelength multiplexing techniques have been developed to efficiently utilize the large storage capacity of the material. However, when transmission holograms are recorded, color cross talk can occur between gratings written by one wavelength and read out by a different wavelength. This effect degrades the efficiency of the wavelength multiplexing technique. In this paper, we explore the variation in the diffraction efficiency as a function of the input angle of the volume hologram gratings. In addition, when the grating writing process is performed in parallel, we observe cascading of the cross talk, leading to higher order diffractions. This effect severely limits the capabilities of performing color signal processing by using multiple wavelengths simultaneously.