Optical information processing by using anisotropic diffraction in BaTiO₃

In this paper, we review the effects and the applications of anisotropic diffraction in a normalcut BaTiO₃. We also report some new applications to optical digital logic operations and optical interconnections. In addition, we discuss two special features in a configuration where the crystal optic axis is normal to the incident plane: (1) the refractive index change can be as large as 2.7 × 10^-4; (2) the diffraction process is permitted when the polarizations of the probe beam and diffracted beam are mutually orthogonal, i.e. one is ordinary polarization and the other is extraordinary. These characteristics cause anisotropic self-diffraction and enable the crystal to record strong volume holograms. We present the applications of these characteristics to optical information processing, including matrix-matrix multiplication, contrast-reversible optical incoherent-to-coherent conversion and the potential applications to optical storage, optical digital logic operation and all-optical interconnection.