High optical coupling efficiency of polymer microlens and pillar on single mode fiber for silicon photonics

Silicon photonics technology has attracted considerable attention these days. However, the low coupling efficiency due to the difference in spot size between silicon photonic (SiPh) chips and single-mode fibers (SMFs) remains a challenging issue. We have already proposed a unique combination of a microlens and a pillar on the facet of SMF. However, the pillar may have difficulty in keeping a single mode for a signal beam of 1. 55 μm wavelength due to air cladding. In this study, we clarified the length of the pillar that can support the single mode through simulations and experiments. By the optimum designing, the spot size as the same level as the SiPh chip was obtained. We could show that our coupling device provides high coupling efficiency with a test sample of SiPh chip, and this device also can be applied to multi-core fibers.