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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.

We provide further details on the calculation method used in the paper "Surface plasmon interferometer in silicon-on-insulator: novel concept for an integrated biosensor" [Opt. Express 14, 7063-7072 (2006)]. Contrary to the claims made in the Comment [Opt. Express 15, 13649-13650 (2007)], the method used does take radiation modes into account and can therefore handle the recapture of optical power from these modes. Convergence studies are provided to support our calculations.

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.

We propose a novel configuration for a highly integrated and highly sensitive optical biosensor. The basic element of the sensor is a surface plasmon interferometer consisting of a thin layer of gold embedded in a silicon membrane. We investigate the performance of the sensor by simulation using eigenmode expansion. We calculate that refractive index changes in the order of 10(-6) RIU should be easily detectable for a component of length 10 microm. Moreover, we illustrate that the operation wavelength of the sensor can be easily tuned to a desired wavelength for a wide range of environmental refractive indices, making our device suitable for chemo- and biosensing.