A digital optical modulator based on an asymmetric Y-branch waveguide is proposed and fabricated by using an electro-optic polymer. The operating point is initially shifted to the off-state utilising the asymmetry in the branch to provide an initial zero-tate with no electrical bias. It has been confirmed that the high extinction ratio can be obtained with a low drive voltage. An extinction ratio of 25 dB is demonstrated for a drive voltage of 20V using a polymer, PMMA-DR1 with r(33) of 5pm/V at 1.3 mum.