Researchers of the of the ETH University (Zurich Switzerland), the Inter-university Research Center IMEC (Leuven, Belgium), the Lehigh University (USA) and the University of Karlsruhe (Germany) have succeeded in manufacturing an optical waveguide structure with highly non-linear behavior and ultra-fast performance. Since in these devices, photonic signals do no longer need to be converted to electronic ones, they are regarded as a key element to all-optical signal transport. In order to achieve that goal, the researchers took the silicon-organic (hybrid (SOH) approach, combining standard CMOS processing, deep ultraviolet lithography and organic molecular beam deposition.

The devices in question is a tiny SOH waveguide only 4mm long — but with a record nonlinearity coefficient of 10⁵ (Wkm)^-1 in the 1.55 µm telecommunications window. This piece of silicon is announced by the researchers as proof of the SOH concept, and it made it possible to confirm for the first time the record values predicted by theory.

The researchers mixed four signals with data rates of 42.7 Gbit/s each to achieve a multiplexed 170.8 Gbit/s signal — the fastest silicon photonic optical signal processing demonstrated to date. According to the researchers, the experiment proved the viability of SOH waveguides for all-optical processing of high-bandwidth telecommunication signals. In particular, the researchers were able to overcome existing obstacles in all-optical switching due to slow dynamics. Hitherto, the data rate achieved by using bare silicon waveguides was limited to about 40 Gbit/s. The ability of organic material used to homogenously fill the slot between the waveguides is a key feature of the deposition process.

The silicon circuits were designed by researchers of the Karlsruhe University and fabricated on IMECs silicon photonics platform through the ePIXfab service, a European funded initiative coordinated by IMEC.