Polarization independent grating coupler for silicon-on-insulator waveguides

A polarization independent grating coupler for coupling the light from an optical fiber into a silicon-on-insulator (SOI) waveguide with a coupling efficiency independent of the polarization of the incident light was proposed. Such a polarization independent grating coupler can be achieved by superimposing the grating couplers which were originally designed for coupling solely the TE and the TM modes. Furthermore, it may have the advantage of being fabricated by a single etching step.