AlO bonding: a method of joining oxide optical components to aluminum coated substrates

With the increased use of photonic packages, there are needs for reliable and low cost methods of attaching optical components. Packages based on silicon optical bench (SiOB) technology include oxide coated ball-lenses and silica fibers which are generally epoxied in anisotropically etched features of silicon substrates. The reliable attachment of these micro-optical components requires the application of small (approximately 1 nanoliter) quantities of epoxy at precise locations on the substrate. This is a time consuming process and requires considerable operator training and skill. Dispensing too much epoxy can deteriorate the optical performance of the device and dispensing too little results in an insufficient holding power. AlO bonding is an alternative attachment technique, under development, which forms solid-state bonds directly between these oxide-components and aluminum thin film coated silicon optical bench substrates and therefore does not require the handling of additives, such as epoxy, at the bond interface. This paper includes: methods of bonding ball-lenses and fibers; an interfacial analysis and proposed bonding mechanism derived from SEM/metallographic photomicrographs and thermodynamic data; destructive test results as a function of bonding and material parameters and; in situ loss measurements through AlO bonded components (multi-, single mode fibers and ball-lenses) during the bonding procedures and subsequent thermal cycling (-40 to 80°C and from ambient to -195.8°C) tests