Light coupling between vertical III-As nanowires and planar Si photonic waveguides for the monolithic integration of active optoelectronic devices on a Si platform.

We present a new concept for the optical interfacing between vertical III-As nanowires and planar Si waveguides. The nanowires are arranged in a two-dimensional array which forms a grating structure on top of the waveguide. This grating enables light coupling in both directions between the components made from the two different material classes. Numerical simulations show that this concept permits a light extraction efficiency from the waveguide larger than 45% and a light insertion efficiency larger than 35%. This new approach would allow the monolithic integration of nanowire-based active optoelectronics devices, like photodetectors and light sources, on the Si photonics platform.

Continuously tunable delay line based on SOI tapered Bragg gratings.

The realization of an integrated delay line using tapered Bragg gratings in a drop-filter configuration is presented. The device is fabricated on silicon-on-insulator (SOI) rib waveguides using a Deep-UV 248 nm lithography. The continuous delay tunability is achieved using the thermo-optical effect, showing experimentally that a tuning range of 450 ps can be obtained with a tuning coefficient of -51 ps/°C. Furthermore the system performance is considered, showing that an operation at a bit rate of 25 Gbit/s can be achieved, and could be extended to 80 Gbit/s with the addition of a proper dispersion compensation.

Tunable Bragg reflectors on silicon-on-insulator rib waveguides.

We present the design, fabrication and characterization of Bragg reflectors on silicon-on-insulator rib waveguides. The fabrication is based on a new double lithographic process, combining electron-beam lithography for the grating and photolithography for the waveguides. This process allows the realization of low loss reflectors, which were fully characterized. The influence of the etching depth and of the waveguide geometry on the reflector performance is considered. We demonstrate a reflectivity larger than 80% over a bandwidth of 0.8 nm with an insertion loss of only 0.5 dB. A thermal tunability of the device is also considered, showing that a shift of the reflected wavelength of 77 pm/K is possible.