1 May 2015 Fiber-chip edge coupler with large mode size for silicon photonic wire waveguides
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Fiber-chip edge couplers are extensively used in integrated optics as one of the key structures for coupling of light between planar waveguide circuits and optical fibers. In this work, a new fiber-chip edge coupler concept with large mode size for coupling to submicrometer silicon photonic wire waveguides is presented. The coupler allows direct coupling to conventional SMF-28 optical fiber and circumvents the need for lensed fibers. We demonstrate by simulations a 95% mode overlap between the mode at the chip facet and a high numerical aperture single mode optical fiber with 6 μm mode field diameter (MFD). We also demonstrate a modified design with 89% overlap between the mode at the chip facet and a standard SMF-28 fiber with 10.4 μm MFD. The coupler is designed for 220 nm silicon-oninsulator (SOI) platform. An important advantage of our coupler is that large mode size is obtained without the need to increase buried oxide (BOX) thickness, which in our design is set to 3 μm. This remarkable feature is achieved by implementing in the SiO2 upper cladding two thin high-index Si3N4 layers. The high-index layers increase the effective refractive index of the upper cladding layer near the facet and are gradually tapered out along the coupler to provide adiabatic mode transformation to the silicon wire waveguide. Simultaneously, the Si-wire waveguide is inversely tapered along the coupler. The mode overlap at the chip facet is studied using a vectorial 2D mode solver and the mode transformation along the coupler is studied by 3D Finite-Difference Time-Domain simulations. The couplers are optimized for operating with transverse electric (TE) polarization and the operating wavelength is centered at 1.55 μm.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Martin Papes, Martin Papes, Pavel Cheben, Pavel Cheben, Winnie N. Ye, Winnie N. Ye, Jens H. Schmid, Jens H. Schmid, Dan-Xia Xu, Dan-Xia Xu, Siegfried Janz, Siegfried Janz, Daniel Benedikovic, Daniel Benedikovic, Carlos A. Ramos, Carlos A. Ramos, Robert Halir, Robert Halir, Alejandro Ortega-Moñux, Alejandro Ortega-Moñux, André Delâge, André Delâge, Vladimír Vašinek, Vladimír Vašinek, } "Fiber-chip edge coupler with large mode size for silicon photonic wire waveguides", Proc. SPIE 9516, Integrated Optics: Physics and Simulations II, 95160K (1 May 2015); doi: 10.1117/12.2181547; https://doi.org/10.1117/12.2181547

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