Optical coupling of planar III-V pin photodiodes and SOI waveguides using an integrated BCB prism

Vertical hybrid integration of photodiodes (PD) and silicon-on-insulator (SOI) waveguides has been investigated. To this end, InP-based planar detectors were used onto which a polymer prism was formed to turn the light beam into the vertical direction. The photodiodes were flip-chip mounted onto a SOI waveguide platform using thermo-compression bonding. Comparable high responsivity of around 0.75 A/W was obtained when light was coupled directly into the prism as well as via a SOI waveguide. The responsivity for SOI integrated PDs was found to depend only to a minor extent on input wavelength and polarization. PD bandwidth of up to 10 GHz was measured. The investigated optical coupling scheme proved to work well also when integrating a PD with an array of ten SOI waveguides which are combined with a star coupler.