Investigation on butt-coupling of VCSEL into PCB integrated waveguides

Optical interconnections on printed circuit boards are a promising approach to increase the bandwidth in future links. Polymer waveguides are one possible solution for creating such optical connections. The coupling of a light source into such a structure is a crucial point in optical interconnection to obtain low transmission loss. The paper shows the butt-coupling conditions between a vertical cavity surface emitting laser (VCSEL) and a highly multimode PCB integrated waveguide realized using "waveguides-in-copper" technology. Two types of VCSELs are used - a lensed one and a naked laser chip without any optics. The influence of lateral and axial laser displacement on coupling efficiency is demonstrated. One the basis of this experiment, the optimal mutual position of the laser and the waveguide can be found for acceptable quality of transmission.