An electro‐optic polymer intensity modulator designed in the heavily multimode region but operating as a quasi‐single mode waveguide has been demonstrated. The device relaxes much of the trade‐off relationship between the modulation voltage and coupling efficiency without the sacrifice of the modulation extinction ratio. The device poled at 1.5 MV/cm shows half‐wave voltage–length product of 7.2 V cm, modulation extinction ratio better than 20 dB, and mode diameters of about 4 and 9 &mgr;m in vertical and lateral directions, respectively. ©1996 American Institute of Physics.