A novel polarizer with a silver nanoribbon added into a traditional waveguide directional coupler is designed to realize the polarized output of TE mode.A high extinction ratio can be obtained because of the selectivity of surface plasmon polaritons(SPPs)on polarization.The effects of the polarizer parameters on coupling efficiency and extinction ratio are discussed.Simulation results indicate that the coupling efficiency for TE mode can reach about 95%,but only 3% for TM mode,with the extinction ratio of TE mode about 15 dB when the light wavelength is 1550 nm.The polarizer may have potential applications in photonic integrated circuits and quantum information technology.
A multilevel grating coupler based on silicon-on-insulator (SOI) material structure is proposed to realize the coupling between waveguide and waveguide or waveguide and fiber. This coupler is compatible with the current fabrication facilities for complementary metal oxide semiconductor (CMOS) technology with vertical coupling. This structure can realize coupling when the beams with transverse electric (TE) polarization and transverse magnetic (TM) polarization are incident at the same time. The influences of the grating coupler parameters including wavelength, the thickness of waveguide layer, the thickness of SiO2 layer and the number of steps on the TE mode and TM mode coupling efficiencies are discussed. Theory researches and simulation results indicate that the wavelength range is from 1533 nm to 1580 nm when the TE mode and TM mode coupling efficiencies are both more than 40% as the grating period is 0.99 μm. The coupling efficiencies of the incident TE and TM modes are 49.9% and 49.5% at the wavelength of 1565 nm, respectively, and the difference between them is only 0.4%.
