CMOS-Compatible Polarization Splitter for 3-D Silicon Photonic Integrated Circuits

To achieve intra-chip three-dimensional (3-D) integration of silicon photonic circuits, we design a polarization beam splitter based on complementary metal-oxide-semiconductor (CMOS) platform. With the aid of the polarization-dependent nature of the center waveguide in a three-port directional coupler, the device separates the TM- and TE-polarization modes onto different layers of 3-D silicon photonic circuits. Numerical simulations with a full vectorial beam propagation method exhibit that we can obtain a 10 μm-long polarization splitter with extinction ratio better than 20 dB on the entire C-band. The optical device without the vertical offset can serve as a horizontal polarization splitter with nearly the same optical characteristics. We conclude that the proposed polarization beam splitter is compatible not only with the CMOS structure but also with the CMOS fabrication process.