A two-port polarization-insensitive coupler module between single-mode fiber and silicon-wire waveguide

A two-port polarization-insensitive single-mode fiber-silicon wire-waveguide coupler module, 5.3 × 3.4 × 0.7 mm(3) in size, is realized. The spot-size converter (SSC) involved utilizes a concatenated horizontal up-taper and vertical down-taper. Measured coupling losses between the fiber and the silicon-wire waveguide of the E(11)(y) and E(11)(x) modes of the SSC are 2.8 and 2.7 dB/port, respectively. The device platform is planar, robust, and easy to fabricate with conventional lithography.