Ultrashort Polarization Splitter Using Two-Mode Interference in Silicon Photonic Wires

An ultrashort polarization splitter based on the zero-gap directional coupler is proposed and realized. Its interference section is 8.8 mu m long. It is also shown that the length of the interference section can be reduced to about 2.1 mu m. The crosstalk for both transverse-electric (TE) and transverse-magnetic (TM) polarizations is 16 dB at a wavelength of 1.55 mu m. The extinction ratios of TE and TM polarizations are 18.2 and 13.7 dB, respec_ tively. The device has 3-dB bandwidth of 43 mn in TE polarization and 50 nm in TM polarization with the center wavelength at 1.55 mu m.