Abstract: The present invention relates to a multi-layer optical planar waveguide which is vertically coupled using multimode-interference couplers and to the method of manufacturing the same. The purpose of this invention is to increase the degree of integration on the multi-layer optical planar waveguide by applying the concept of via holes of the multi-layer printed circuit board (MLPCB) used in electronic circuits to the optical waveguide devices. According to the present invention, particularly, a multimode interference coupler of a stepped structure has the higher coupling ratio at relatively short length of interference than the usual multimode interference coupler. The present invention can implement a multimode interference coupler at a specialized spot while reducing evanescent field interference between the upper and lower optical waveguides out of the spot by separating the layers enough.

Abstract: Disclosed is a method of forming a silica layer for an optical waveguide. The present invention includes the steps of preparing a chamber having a magnetic coil, a gas supply unit, and a support and injecting a reactant gas in the chamber to deposit the silica layer on a substrate mounted on the support by high density plasma chemical vapor deposition. The present invention provides the high deposition ratio of the silica layer since the ionization of the reactant gas proceeds fast due to the high density plasma induced by the magnetic coil. Moreover, the sputtering process by the inert gas and the silica layer depositing process are simultaneously carried out to provide the silica layer with a high deposition ratio and high density, whereby additional annealing is unnecessary as well as the process can be carried out at a low temperature to fabricate various silica-polymer mixed waveguide.