Efficient TE/TM spot-size converter for broadband coupling to single mode fibers

We present the novel design of a spot-size converter (SSC) for high efficiency coupling between a conventional single-mode fiber (SMF) and a standard silicon nanowire. Our design involves evanescent coupling between a stack of Si3N4/SiO2 alternating layers and a standard silicon nanowire. The proposed SSC coupler demonstrates highly broadband performance with a polarization dependence of less than 0.62 dB and an expected taper loss of less than 1.0 dB, over 100 nm bandwidth ranging from 1.5 to 1.6 mu m. To the best of our knowledge, the proposed SSC achieves the highest broadband coupling for both polarizations between a fiber with a large mode-field diameter (i.e., SMF-28) and a standard silicon nanowire. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement