Analysis and experiment on phase-conjugate reflectivity of CAT mirror

The effects that the arrangement of light rays inside the photorefractive crystals have on the reflectivity of CAT miners are analyzed anew. Experiments are performed using BaTiO3 crystal and the measured results are compared with those of numerical calculations. First, for generation of beam fanning in photo-refractive crystals, three different cases of generation are considered, i.e., at the plane of incidence of the crystal, in the range of maximum coupling coefficient, and in the range of maximum coupling strength. Next, the light-ray incident conditions (incident position, incident angle, and beam radius) and the generating position of beam-fanning associated with variations of light-ray arrangement inside the photorefractive crystal are simulated. In each of these three cases, the phase-conjugate reflectivity is estimated via numerical calculations from which the effects that light-ray arrangement have on reflectivity is clarified. Finally, experiments are carried out using a BaTiO3 crystal and the measured data are compared with the simulated results. It is shown that if the angle of the incident beam with respect to the crystal is large, beam-fanning is generated at the position where the coupling coefficient is at its maximum. When the angle of incidence is small and in the range of small values of the position of incidence, beam-fanning occurs in the plane of incidence of the crystal. Using this analysis, the light-ray arrangement required in achieving high phase-conjugate reflectivity is clarified.