An optical modulator is provided. The optical modulator includes a ridge-shaped active region comprising a plurality of alternating high and low index layers. The ridge-shaped active region is used to confine a selective optical mode for optical modulation. A plurality of oxidized layers positioned so as to confine the selective optical mode in the middle region of the ridge-shaped active region. The oxidized layers enable the optical modulator to withstand high operating voltages both in reverse and forward bias without concern of breakdown or carrier loss.