Abstract

Optical coupling from single mode fibers to integrated waveguides of semiconductor optoelectronic devices with less than 0.5 dB packaging loss generally requires positioning accuracies on the order of ±0.5 to ±1.5 μm. Laser welding is widely used for fixing because it guarantees long term stability, and it is the preferred method for hermetic packaging [1-3]. Furthermore, no thermal strain on the module parts and precise positioning of the welds are attractive features of this technique. A Nd:YAG laser equipped with fiber guided energy distribution to the welding heads is generally used. However, commercial laser systems do not guarantee a stable distribution of the energy into the different arms. This leads to different volumes and temperatures of the melted material in the weld spots, preventing a simultaneous solidification and cooling process. Hence, an unequal shrinking of the welding spots occurs, resulting in a shift of a few microns of the welded parts, strongly increasing the assembly loss. However, the shrinking of welding spots can be turned into an advantage by using it for readjustment purposes.

© 1994 Optical Society of America