Vertically bent silicon waveguide for high-efficiency optical fiber coupling

Youichi Sakakibara; Yuki Atsumi; Emiko Omoda; Tomoya Yoshida

doi:10.1117/12.2314742

21 May 2018 Vertically bent silicon waveguide for high-efficiency optical fiber coupling

Youichi Sakakibara, Yuki Atsumi, Emiko Omoda, Tomoya Yoshida

Proceedings Volume 10686, Silicon Photonics: From Fundamental Research to Manufacturing; 106860S (2018) https://doi.org/10.1117/12.2314742
Event: SPIE Photonics Europe, 2018, Strasbourg, France

Abstract

In silicon photonics, optical coupling between optical fibers and silicon photonics chips still remains a big issue to be improved. Recently we have developed a new surface coupler consisting of a vertically-bent silicon waveguide using ion implantation as a bending method. This bending method enabled bending of silicon waveguide terminals to the vertical surface direction with curvature radii as small as several μm and bending of propagation direction of light to the surface direction with broadband wavelength property. In our initial studies, to couple the propagated light with optical fibers efficiently, we taper-narrowed the tips of the waveguide terminals from 440 nm to ~200 nm to expand the mode field and obtained a coupling loss of ~2 dB in TE-polarization mode for a lensed fiber with a beam diameter of 2 μm. We are now developing couplers with high coupling efficiencies for 5 μm mode field diameter fibers. Such mode field diameters are available by HNA fibers and position alignment accuracy can be mitigated to a micron level. In addition, HNA fibers can be fusion-spliced to standard single mode fibers. Using 3D-FDTD simulation we have demonstrated that <1dB coupling is possible if the tip of the bent waveguide is taper-narrowed to 50 nm and covered with a lens-shaped SiO₂ dome. In practice, such a structure could be fabricated successfully and 5 dB coupling with a 5 μm mode field diameter lensed fiber has been demonstrated in our initial experiment

Citation Download Citation

Youichi Sakakibara, Yuki Atsumi, Emiko Omoda, and Tomoya Yoshida "Vertically bent silicon waveguide for high-efficiency optical fiber coupling", Proc. SPIE 10686, Silicon Photonics: From Fundamental Research to Manufacturing, 106860S (21 May 2018); https://doi.org/10.1117/12.2314742

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