Low cost packaging of semiconductor laser arrays using passive self-aligned flip-chip technique on Si motherboard

A passive self-aligned packaging technique for semiconductor laser arrays has been realized. Alignment trenches on the laser chip are introduced to enable self-alignment to optical fibers during flip-chip mounting on a structured Si motherboard. The use of the etched Si sidewalls for alignment results in a self-positioning effect, reducing device placing precision, and allows larger tolerances in the motherboard processing. Arrays of 4, 8 and 12 lasers have been flip-chip mounted with a coupling efficiency of -3.4±0.2 dB to cleaved 50/125 μm multimode fiber (MMF) ribbons. The excess loss due to the optical mounting process is <0.3 dB. Coupling to lensed MMF´s results in 1.3±0.2 dB coupling loss. The laser characteristics, such as threshold current and efficiency remain unchanged during packaging and show a very low temperature dependence. A characteristic temperature of 170 K in the range of 25°C to 75°C opens the possibility for applications of these laser modules without active temperature control. Together with the short assembly times of the passive self-alignment, the described technology is very promising for low-cost laser array modules