Patent ID: 8885449

Claim:
A method for fabricating a waveguide structure that includes a light polarization rotator section for converting TE light to TM light, comprising: (a) sequentially depositing a waveguide layer and a hard mask layer on a substrate; (b) patterning the waveguide layer and hard mask layer to give a structure with a lengthwise dimension in a first axis direction that is perpendicular to a cross-track direction, and with a thickness in a down-track direction, and wherein a first section at a first waveguide end has a first width in a cross-track direction, a middle tapered section has a first width at an end that adjoins the first section and a second width less than the first width at a second end, and a third section that is formed between a second end of the waveguide and the second end of the middle tapered section has a second width; (c) etching a middle portion of the third section with ions directed at an angle of about 45 degrees to the substrate such that a portion of the hard mask and waveguide layer along one side of the middle portion are removed and replaced with a sloped side that defines a light polarization rotator section wherein the sloped side connects a top surface with a bottom surface of the middle portion and is formed opposite to a vertical side; and (d) depositing a dielectric layer along the sloped side, vertical side, and on the hard mask layer followed by a chemical mechanical polish process to remove the hard mask and form a top surface of the dielectric layer that is coplanar with a top surface of each of the first section, tapered section, and remaining portions of the third section, and the top surface of the light polarization rotator section.