Resonant two-wave mixing in photorefractive materials with the aid of dc and ac fields Kalinin, V. A. ; Shcherbin, K. ; Solymar, L. ; Takacs, J. ; Webb, D. J. Abstract Publication: Optics Letters Pub Date: December 1997 DOI: 10.1364/OL.22.001852 Bibcode: 1997OptL...22.1852K