Fiber-Core-Matched Three-Dimensional Adiabatic Tapered Couplers for Integrated Photonic Devices

A three-dimensional (3-D) adiabatic tapered coupler is demonstrated to improve light coupling between single-mode fibers (SMF) and an integrated photonic chip. This 3-D taper, made by polymer via a fabrication process using mode extrusion in combination with photolithography, can have a large coupling area matching with a fiber core. For a silicon oxynitride waveguide coupling to a SMF, the measured coupler loss was 3 dB. The fiber misalignment tolerance is 3.5 mu m and 3 to 5 mu m for the lateral and vertical offset, respectively, according to a 3-dB loss window.