Near-Zero Shift Attachment for Optoelectronic Components

High performance laser-based optoelectronic devices commonly feature the use of free-space optical coupling between the laser diode and optical elements such as filters, secondary harmonic generators and optical fibers. A critical challenge in the assembly of such components is maintaining the required optical alignment precision during attachment of the optical subcomponents to a common platform. In the case of devices based on single mode waveguides, the post-attach shift must often be held to less than a few hundred nanometers to achieve the desired optical coupling efficiency. Historically, these tight tolerances have required the use of costly post-work operations such as laser hammering or re-bend to achieve performance objectives. Over the course of designing several such optoelectronic components, we have used and developed a variety of design concepts and assembly processes which have allowed us to achieve these demanding tolerances, often without the use of post-work. UV-curable structural adhesives and Nd:YAG laser spot welding have been used, individually and in combination, to perform the required sub-micron optomechanical attachments. Several approaches which have been successfully used will be described and their relative merits will be compared. In addition, key design and process elements which can impact post-attach shift will be discussed.