Phase properties of χ^(2) gratings in glass

A new method for the measurement of the phase shift between second-harmonic light generated by a bulk glass and the injected second-harmonic seed is presented. A linearly polarized pump and a second-harmonic seed with noncollinear polarizations were used for preparation of cerium-doped lead-silica glass. Independence of the phase shift from the angle between the polarizations of the recording waves is demonstrated, and a phase shift value close to 90 degrees is observed, i.e., the X((2)) grating was in phase with the real ?E(EE)?.