A polarization-diversity wavelength duplexer circuit in silicon-on-insulator photonic wires.

We present a wavelength duplexer based on a compact arrayed waveguide grating (AWG) in silicon-on-insulator photonic wire waveguides. Polarization insensitive operation is achieved through a special polarization diversity approach in which we use 2-D grating fiber couplers as integrated polarization splitters. To mitigate the effects of process variations, we propagated both polarizations in opposite directions through the same AWG with a mere 600x350microm(2) footprint. This resulted in an on-chip insertion loss between -2.1dB and -6.9dB, crosstalk of -15dB, and only 0.66dB polarization dependent loss. This is the first demonstration of a functional polarization-diversity circuit implemented in SOI nanophotonic waveguides, including interfaces to single-mode fiber.

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.

Integration of InP/InGaAsP photodetectors onto silicon-on-insulator waveguide circuits.

The integration of optical functionalities on a chip has been a long standing goal in the optical community. Given the call for more integration, Silicon-on-Insulator (SOI) is a material system of great interest. Although mature CMOS technology can be used for the fabrication of passive optical functionality, particular photonic functions like efficient light emission still require III-V semiconductors. We present the technology for heterogeneous integration of III-V semiconductor optical components and SOI passive optical components using benzocyclobutene (BCB) die to wafer bonding. InP/InGaAsP photodetectors on SOI waveguide circuits were fabricated. The developed process is compatible with the fabrication of InP/InGaAsP light emitters on SOI.

Compact efficient broadband grating coupler for silicon-on-insulator waveguides.

We have designed a high-efficiency broadband grating coupler for coupling between silicon-on-insulator (SOI) waveguides and optical fibers. The grating is only 13 microm long and 12 microm wide, and the size of the grooves is optimized numerically. For TE polarization the coupling loss to single-mode fiber is below 1 dB over a 35-nm wavelength range when using SOI with a two-pair bottom reflector. The tolerances to fabrication errors are also calculated.