In our experiments, an expanded beam from an argon-ion laser is intercepted by a 2-D phase-modifying transparency and then focused into a single BaTiO3 crystal (Fig. 1). The beam enters with polarization parallel to the plane in which the crystal c and a axes lie. It has been already shown that such an arrangement forms a self-pumped phase conjugator.1 The conjugated wave front is produced by a photorefractive phase hologram generated in the crystal volume by the single input beam. Although this hologram and the phase-conjugated wave front can be generated continuously, with subsequent inputs erasing and replacing preceding ones, the holograms themselves have significant lifetimes in the dark. To produce a phase gradient of the input phase-modifying transparency, we form the hologram of the input transparency with illumination incident typically for ~15 sec.
© 1984 Optical Society of AmericaPDF Article