In this paper, we report a quasi-velocity-matched electrooptic (EO) modulatorconstructed by periodic domain inversion technology and the newest experimental resultswith it for generation of ultra-wide optical sideband. The quasi-velocity-matchingbetween phase velocity of microwave and the group velocity of light, not dependins onthe modulation frequency, was etublished by using periodic domain inversion of an EOcrystal LiTaO3. Consequently, long effective interaction length was ontuined at 16.25 GHz to increase the modulation effeciency. As a result, we have obtained modulation index 57 rad and extended the sidebands as wide as 1.85 THz.