Alignment tolerance measurements and optical coupling modeling for optoelectronic array interface assemblies

Alignment tolerance measurements for flip-chip mounted optoelectronic device substrates have been performed, including separation, tilt, and lateral misalignments. A test assembly was fabricated by joining two metallized and lithographically patterned glass substrates with an array of 76 μm dia. 63%Sn-37%Pb solder balls. Measurements indicated poorer alignment than expected, with an average lateral misalignment of 9 μm, and worst case height variation of ±8 μm for laser diode sites interconnecting to a 12-fiber array. These misalignment values are acceptable for coupling to multimode optical fibers, but not single-mode optical fibers. Work is ongoing to improve the alignment tolerance test assembly to provide more accurate results. A multimode optical coupling model using an analytic beam propagation approach has been validated with measurements of multimode fiber-to-fiber coupling. The model is suitable for fiber-to-fiber, laser diode-to-fiber, fiber-to-rectangular waveguide and fiber-to-photodiode interconnections