Passively aligned glass micro-optic bridge for expanded-beam vertical coupling and pluggable Silicon Photonics

Achieving reliable, low-loss optical coupling in the confined space of electronic packages is a key challenge for high-yield co-packaged photonics. While a common method to relax alignment tolerances involves beam expansion, conventional approaches often entail attaching large micro-optic die to the silicon PIC, significantly impacting the overall assembly thickness. Furthermore, precise alignment systems are typically necessary for positioning the micro-optic die with sub-micron tolerances. This article introduces a novel solution to address these challenges: utilizing a glass micro-optic bridge passively aligned to a silicon PIC through existing mechanical alignment features. The micro-optic bridge contains curved micromirrors which allow for vertical coupling in and out of the PIC, enabling the use of existing low loss edge couplers along with facilitating high speed optical test. The optical bridges contain mechanical alignment features that allow for passive placement onto the PIC, allowing for a simplified assembly process with relaxed tolerances. Beam expansion to approximately 30 μm was achieved, and an average excess loss of 1.32 dB was observed when coupled through a two-mirror periscope based system.