A simple passive-alignment packaging technique for laser diode modules

Abstract

A simple passive-alignment packaging technique has been developed for the fabrication of a laser diode connection to a singlemode fiber pigtail. The fabrication begins with a multimode fiber soldered in a U-groove with 5 mu m tolerance. Then the laser chip with a junction-up die-bond is passively aligned to a multimode fiber and converted into a singlemode fiber. The tolerance as measured for the multimode fiber at 10% loss of maximum coupling from the laser diode is 11 mu m. Because the tolerance of the multimode fiber from the laser chip is larger (11 mu m) than that of the fiber in the U-groove (5 mu m), this passive alignment is easily obtained. In contrast to other passive-alignment techniques, the advantages of this technique are that it is less sensitive to transverse misalignment and requires no complicated alignment marks. From laser to multimode fiber a coupling efficiency of greater than 80% and a bandwidth of greater than 1 GHz have been achieved. In this package, the overall coupling efficiency from laser to singlemode fiber is 16%, The resulting laser module with compact size and fewer components should make it highly suitable for use in low-cost telecommunication applications, (C) 1998 Elsevier Science S.A. All rights reserved.