We present a highly efficient 1-D grating structure that serves to couple light between standard optical fibers and single-mode waveguides in the silicon-on-insulator platform and to split both orthogonal polarization states. The efficiency of the fabricated coupler is enhanced by a backside metal mirror and reaches −2.4 dB for both polarizations at 1552 nm with an extinction ratio > 25 dB in a wide wavelength range. The efficiency can be theoretically improved to −1.1 dB when optimizing the

more »

... ber of periods and using a nonuniform grating. Index Terms-Grating coupler, metal mirror, photonic integrated circuits, polarization splitter, silicon-on-insulator.