(EN) A method to form a vertical waveguide taper in a planar waveguide includes providing a substrate (10), forming a cladding layer (12) or the substrate, forming a core layer (14) on the cladding layer (12) . A protective layer (16B) with an opening is formed on the core layer (14), the opening exposing a portion of the core layer. A chemical mechanical polishing process is performed so that dishing occurs in the exposed portion, forming a depression (31) , in the core (14) with a sloped sidewall. In one embodiment, the core layer (14) is then patterned so that a portion of the core layer is removed to about the depth of the depression. This removed portion includes a part of the core layer containing the depression. The resulting structure includes an unetched sloped surface that transitions to a substantially planar etched surface. The core layer is patterned and etched again to form the waveguide, with the sloped surface forming part of the taper.
