High Optical Coupling Scheme in LD Modules with Silicon Platform Technology

Kazuhiro TANAKA
Kazunori MIURA
Shouichi OGITA
Mitsuhiro YANO

IEICE TRANSACTIONS on Electronics   Vol.E80-C    No.1    pp.107-111
Publication Date: 1997/01/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Devices, Packaging Technology, and Subsystems for the Optical Access Network)
silicon platform,  optical coupling,  passive alignment,  marker,  laser diode,  spot size transformer,  

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Laser module fabricated with silicon platform technology is very attractive for low-cost modules. The technology enables passive optical alignment of an LD to an optical fiber. Our marker design for passive alignment allows positioning accuracy within 1 µm of LD. However, coupling efficiency is a key issue because that by conventional butt coupling scheme is low with about 10 dB coupling loss. We investigated optical coupling characteristics in various types of coupling scheme: conventional flat end fibers, cone fibers, integrated GRIN rod lenses on the platform and the coupling with new-type LDs integrated with spot size transformer. Improvement of coupling efficiency with 3 dB and 7.5 dB compared to flat-end fiber is achieved by using the cone fiber and the GRIN rod lens, respectively, although 1-dB coupling tolerances for alignment deteriorated with these schemes. We obtained high efficient coupling with 3.5 dB coupling loss and wide alignment tolerance of 2.3 µm simultaneously with a new-type LD integrated with spot size transformer owing to its expanded spot size characteristics.