Relaxed-tolerance optoelectronic device packaging

The authors present an approach to single-mode fiber coupling which results in relaxed alignment tolerances during the package assembly process. The authors use a ball lens to couple from the optical device either directly to single-mode fiber (SMF), or indirectly to SMF through a fiber lens. The ball lens is aligned and mounted in the first assembly stage. The lens is aligned and fixed either mechanically or semiactively. In the second stage of assembly, the SMF is aligned so as to compensate for any small misalignments of the ball lens. The authors have achieved coupling efficiencies of 33-40 % with this coupling scheme. It has been used for coupling to standard laser diodes and to near-traveling wave optical amplifiers. Fiber-to-fiber gains of 8.5-10 dB have been achieved with packaged devices. The approach provides some versatility with respect to the placement of passive optical components inside the package