The coupling efficiency between laser diode arrays or OEIC components and single-mode fiber ribbons drops rapidly with increasing misalignment tolerance. There are trade-offs between the allowed minimum coupled power and the cost of establishing the required alignment. We demonstrate how tapered polymer waveguides may be used to match the laser mode to the fiber mode, resulting in a module with decreased alignment requirements for a given coupling efficiency. Waveguides with tapered mode profiles have been constructed using photobleaching of a guest/host dye/polymer system. Amoco 4212 polyimide doped with DCM dye was chosen as the waveguide material due to its good thermal stability, and its simple processing which allows multilayer waveguides to be readily fabricated. In particular, waveguides which simultaneously taper the mode both laterally and vertically have been designed. This waveguide system is compatible with assembly of the laser and waveguide components into a module by flip-chip soldering. Our solder self-alignment technique achieves accurate alignment of touching chips through an understanding of the dynamics during bonding.
A self-pulling soldering technology has been demonstrated for assembling liquid crystal on silicon (LCOS) spatial light modulators (SLMs). One of the major challenges in manufacturing the LCOS modules is to reproducibly control the thickness of the gap between the very large scale integrated circuit (VLSI) chip and the cover glass. The liquid crystal material is sandwiched between the VLSI chop and the cover glass which is coated with a transparent conductor. Solder joints with different profiles and sizes have been designed to provide surface tension forces to control the gap accommodating the ferroelectric liquid crystal layer in the range of a micron level with sub- micron uniformity. The optimum solder joint design is defined as a joint that results in the maximum pulling force. This technology provides an automatic, batch assembly process for a LCOS SLM through one reflow process. Fluxless soldering technology is used to assemble the module. This approach avoids residues from chemical of flux and oxides, and eliminates potential contamination to the device. Two different LCOS SLM designs and the process optimization are described.
An integrated tool has been developed to predict how vertical cavity surface emitting laser (VCSEL) light output power is affected by packaging components. The set that has been developed includes modeling tools for devices and packages. The integrated tool can be useful for choosing an optimum specific package design for a VCSEL structure and to predict its characteristics in different packages under a variety of operating conditions. In this paper the integrated tool has been applied to study how VCSEL light output power is affected by different assembly technologies and packaging materials.