Silicon oxynitride in integrated optics

I . INTRODUCTION Integrated optics (IO) devices for application in telecommunication are highly demanding on low insertion loss, efficient fiber-to-chip coupling, high compactness (small bending radii) and polarization independent operation. In most operating communication devices developed within the last decade, low-index contrast waveguiding structures have been applied El]. The large channel cross-section of these waveguides matches well with the standard optical fiber, but due to the low index contrast large bending radii are required for low bend losses leading to a low integration density. The compactness of 10 devices is significantly increased when applying high-index contrast waveguiding structures. Although for these structures the fiber-to-chip coupling efficiency is generally low, this parameter can be significantly improved by a proper design of the fiber-to-chip interface. Silicon oxynitride (SiON) grown by chemical vapor deposition (CVD) is a material which is well-suited for the realization of high contrast waveguides, since the range over which the refractive index of this material can be tuned (1.46-2) is large. In this contribution we will shortly review on the state of the art of our SiON deposition process and the important properties of this material. Then, the development and realization of a SON-based high contrast channel structure having the potential of filfilling all the above given demands arising from the telecommunication application will be discussed. Finally, results of the application of this structure in a WDM add-drop device will be shown.