Optimizing fiber coupling with a quasi-passive microoptical bench

While the silicon microoptical bench with purely passive locational features was an attempt at breadboard-like integration for photonic applications, it failed to provide the high-precision alignment required for efficient light coupling between devices and/or fibers. To optimize the final alignment without the introduction of on-board active actuators or external high-precision manipulators, we have developed and demonstrated a low-cost, micromachined optical bench with quasipassive locational features capable of submicron alignment optimization. The concept capitalizes on inherent residual tensile stresses produced during the stoichiometric Si₃N₄ thin-film deposition process. By selectively trimming stress element on either side of a suspended platform, the equilibrium position can be biased to one side or another, enabling high-resolution relative motion between the suspended platform and the base. We have demonstrated, as a first attempt, high-efficiency fiber-to-fiber alignment using this concept. [1556].