PECVD grown multiple core planar waveguides with extremely low interface reflections and losses

A novel and generic method for fabricating silicaon-silicon planar lightwave circuits with cores composed of two or more different types of glasses is described. The basic process technologies used are silane/germane/nitrous-oxide based plasma enhanced chemical vapor deposition and fluorine based reactive ion etching. Very high-quality interfaces between the different core glasses are obtained with interface losses as low as 0.022±0.012 dB and reflection levels below -80 dB. This technique adds flexibility and ease to the design of complex silica planar waveguide components, allowing, e.g., independent optimization of amplifying and passive sections in lossless devices based on erbium-doped planar waveguides.