Amplified phase-conjugate beam reflection by four-wave mixing with photorefractive Bi12SiO20 Crystals Rajbenbach, H. ; Huignard, J. P. ; Refrégier, Ph. Abstract Publication: Optics Letters Pub Date: December 1984 DOI: 10.1364/OL.9.000558 Bibcode: 1984OptL....9..558R