Vertical silicon waveguide coupler bent by ion implantation.

We propose and demonstrate that vertically curved waveguides (VCWs) enable vertical coupling between silicon wire waveguides and optical fibers with low wavelength dependence and polarization dependence for wide telecommunication wavelength band light. To bend these VCWs, we implanted silicon ions into silicon wire cantilevers from the vertical direction. The internal stress distribution that was induced by ion implantation drove the bending force, and we achieved vertical bending of the waveguides, with curvature radii ranging from 3 to 25 μm. At a radius of curvature of 6 μm, we obtained a coupling loss of 3 dB using a lens fiber.