Contrast-reversible photorefractive incoherent-to-coherent optical converter by using an anisotropic strong volume hologram

Incoherent-to-Coherent Conversion by Use of the Photorefractive Beam-Fanning Effect and Amplification by Two-Wave Coupling in a Photorefractive Ba(1-x)Sr(x)TiO(3) Crystal

Incoherent-to-coherent conversion by use of the photorefractive beam-fanning effect and amplification by two-wave coupling have been demonstrated experimentally in a photorefractive Ba(1-x)Sr(x)TiO(3) crystal. The converted coherent image is amplified by 60x. The resolution of the amplified coherent image is ~28 line pairs/mm. A notable advantage of the method is that incoherent-to-coherent conversion and coherence amplification of the converted coherent image are realized simultaneously in a photorefractive crystal.

Optical symmetry filtering by use of anisotropic self-diffraction in BaTiO3 crystals

We propose what we believe to be a novel and simple method for optical symmetry filtering, using anisotropic self-diffraction in BaTiO(3) crystals. This method allows us to distinguish a centrosymmetric pattern from a noncentrosymmetric pattern easily with scale invariance. It is self-referential; no extra reference element is required. Both the theory and the experiment are demonstrated.

High-resolution incoherent-to-coherent conversion by use of the photorefractive fanning effect

We demonstrate that high-resolution incoherent-to-coherent conversion can be carried out in an incoherent-to-coherent converter based on the photorefractive fanning effect. The output coherent image has the same direction as the incident coherent beam, and thus the resolution is not limited by the grating diffraction. We obtained a resolution as high as 90.5 line pairs/mm in this experiment. The transmittance of the coherent beam relative to the intensity of the incoherent beam was measured. We also theoretically estimated the resolving power with respect to the interaction length. The numerical results agree well with the experiments.

Photorefractive Incoherent-to-Coherent Optical Converter Based on Anisotropic Self-Diffraction in BaTiO(3)

A photorefractive incoherent-to-coherent optical converter (PICOC) is demonstrated; conversion is accomplished by anisotropic self-diffraction in BaTiO(3). The setup of the PICOC is easy, and only two writing beams are required. The diffraction efficiency reaches 50%, and the resolution is 22 line pairs (lp)/mm in a typical-size crystal. Further, the resolution reaches 40 lp/mm when a BaTiO(3):Rh crystal of thickness 1.2 mm is used, and the diffraction efficiency is as high as 51%. The resolution of the PICOC can be increased effectively by reduction of the crystal thickness with no penalty for low diffraction efficiency.

Incoherent-to-coherent conversion by use of the photorefractive fanning effect

A dynamic incoherent-to-coherent converter using the photorefractive fanning effect is demonstrated in a BaTiO(3):Ce crystal, and high-quality positive replicas of the incoherent image are obtained with a resolution of 32line pairs/mm. In this method the incoherent image-bearing beam modulates the transmission intensity of the coherent beam directly, and no readout beam is required. When the intensity ratio of the incoherent beam to the coherent beam is smaller than 5, the transmission intensity of the coherent beam increases almost linearly with increased intensity of the incoherent beam.