Compact TE/TM polarization splitters for 1.31 and 1.55 μm wavelengths in LiNbO3 photonic wires

Ultra-compact TE/TM polarization splitters in LiNbO3 photonic wires with same bending waveguide in input and output transition regions at 1.31 μm and 1.55 μm wavelengths have been proposed, respectively. Their operating principles are based on the directional coupling mode. Their optimization designs are achieved by using commercial software COMSOL Multiphysics. Calculated steady-state field distributions indicate that guided lightwaves in both quasi-TM and quasi-TE polarizations can be spatially separated from different output waveguides ports. The transmittances of quasi-TE and quasi-TM polarization at 1.31 μm wavelength are 90% and 88.5%, respectively. And that at 1.55 μm are 88.6% and 84.7%, respectively. The total lengths of the devices for 1.31 μm and 1.55 wavelengths are 47 μm and 36.52 μm, respectively. Moreover, the coupling length dependences of the transmittances, the optical transmission bandwidths, and fabrication sensitivities are evaluated, respectively. The simple and compact polarization splitters are expected to be applied to highly dense LN photonic integrated circuits.