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Code: EP116

Description

The lecture examines optoelectronics packaging in the context of optical communications via monomode fibre, requiring fibre interface (i.e., light I/O) with sub-micro precision, high frequency constraints on package dimensions, and combinations of unusual materials. The solution requires effective achievement of optical, electrical, thermal, mechanical, reliable and low cost solutions. Typical dimensions are: laser spot < 1 µm, photodiode active area ~ 30-50 µm, waveguide component ~ 2-8 µm, fibre core ~ 8 µm. Laser to fibre coupling requires 1-2 µm alignment tolerance for 10-20% coupling with butt fibre. Lensed fibre achieves 30-60% coupling but with alignment tolerance < 1 µm. Alignment includes self alignment and active alignment. Once aligned, the fibre is fixed either by adhesive, solder or laser weld. Laser welding provides localised heating, "cold" fixing, which is rigid and stable, but has a high purchase cost. The fibre is housed in a metal support tube and welded by a pulsed Nd:YAG laser. The metal is stainless steel, and it is important that no extraneous plating or contaminants are present. Practical techniques are described and illustrated by pictures and a video sequence. Precautions include controlling and minimising stray capacitance. The future outlook includes: emphasis on low cost, multi-fibre attachment, waveguide packaging, Si motherboards, neural networks, backplane interconnects, and optical switching.