an integrated optical arrangement having at least one optical waveguide integrated a substrate of semiconductor material , characterized by the waveguide being a rib waveguide comprising the p - doped material disposed on a substrate which contains a waveguiding layer which is either an n - doped or an undoped material , said arrangement having either a pn or a pin junction between the p - doped material of the rib and the n - doped or undoped material of the waveguiding layer . in addition , a method for forming the various layer is disclosed .