Hybrid Integration of VCSEL and 3-μm Silicon Waveguide Based on a Monolithic Lens System

We design an optical interface system for vertical coupling between vertical-cavity surface-emitting lasers (VCSELs) and 3- \mu \text{m} silicon waveguides. The system includes a photoresist lens and a total internal reflection mirror, which allows for passive alignment and flip-chip bonding (FCB) of VCSELs. The simulated coupling loss is 0.7 dB, in optimal conditions, which increases to 1 dB when 3- and 20- \mu \text{m} alignment tolerances are considered in lateral and longitudinal directions, respectively. The system is built by post-processing lens and metallic wiring on the backside of a 3- \mu \text{m} silicon photonic platform. After FCB and embedding of the VCSELs, the system performance is characterized, and VCSEL-to-waveguide coupling efficiency of -7.5 dB is obtained.