Vertical fiber-to-waveguide coupling using adapted fibers with an angled facet fabricated by a simple molding technique.

Vertical coupling between silicon-on-insulator waveguides and optical fibers is achieved using adapted fibers with an angled facet. The proposed coupling scheme is demonstrated for waveguides containing uniform one-dimensional grating couplers. A coupling efficiency of 32% and a 1 dB bandwidth of 32 nm are measured at a wavelength of 1550 nm. We demonstrate single-step fabrication of these fibers using a simple molding technique.

Efficient, broadband and compact metal grating couplers for silicon-on-insulator waveguides.

Compact metal grating couplers for efficient and broadband coupling between optical fibers and silicon-on-insulator waveguides are proposed and demonstrated. Simulation results for silver, gold, aluminum and copper grating couplers are presented. Using a uniform silver grating, coupling efficiencies are calculated as high as 60 % at a wavelength of 1.55 mum. Metal grating couplers require only one single etching or lift-off step and are therefore very easy to fabricate. As a proof of principle, a gold grating coupler for near-vertical fiber-to-waveguide coupling was fabricated using e-beam writing and lift-off, demonstrating 34 % coupling efficiency and a 1 dB-bandwidth of 40 nm. Measurement data and simulation results are in good agreement.