We report the fabrication of monolithic phase grating modulators in single crystal 0.67PMN-0.33PT. Diffraction was observed for a period (b) to thickness (T) ratio >2.5. Very strong diffraction was obtained at a period of 250 mum, electrode width of 100 mum, and a substrate thickness of 50 gm. Under these conditions, the overall diffraction efficiency into the first orders at optimal voltage applied to the modulator was about 57%. Modulators containing linear arrays of elements are attractive alternatives to acousto-optic modulators, and rectangular arrays may be used for image projection. (C) 2004 American Vacuum Society.