Electrooptic polymer-based modulators have been investigated intensively due to their potential applications in optical communication systems. In this paper, we report a polymeric modulator with a domain-inverted Y-coupler configuration. Both of the modulation depth and linearity were improved due to the novel device structure. The Y-coupler modulator was automatically set at 3dB point with no need of DC bias, which eliminate the DC drift phenomena in Mach-Zehnder or co-direcitonal modulators. At the same time, a domain- inversion poling technique was developed, which can be used to fabricate other type of active EO devices in the future.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.