An integrated tunable transmitter on silicon has been demonstrated for the first time, paving the way for fully integrated transceivers.
The transmitter has been developed by CEA-Leti, III-V lab, a joint lab of Alcatel-Lucent Bell Labs France and Thales Research and Technology. The transmitter incorporates a hybrid III-V/Si laser-fabricated by direct bonding, which exhibits 9nm wavelength tunability and a silicon Mach-Zehnder modulator with high extinction ratio (up to 10dB), leading to a bit error rate performance at 10Gb/s. The results were obtained as part of the European funded project HELIOS. The University of Surrey designed the modulator, while Ghent University-imec designed the laser. CEA-Leti and III-V lab have also demonstrated single wavelength tunable lasers, with 21mA threshold at 20°C, 45nm tuning range and side mode suppression ratio larger than 40dB over the tuning range. The results will be overviewed during the Optical Fiber Communication conference 2012 in Los Angeles (USA) on March 4 to 8, 2012. Both organisations believe they have made a significant breakthrough in silicon photonics by integrating complex devices on the same chip, such as a fully integrated transmitter working above 10Gb/s or a tunable single wavelength laser. Silicon photonics technology has the potential to bring large scale cmos manufacturing to traditional expensive photonic devices. One obstable to silicon photonics is the lack of optical sources on silicon – the base material on cmos. Martin Zirngibl, Bell Labs Physical Technologies Research leader, said: "We can overcome this problem by bonding III-V material, necessary for active light sources, onto a silicon wafer and then coprocessing the two, thus accomplishing two things at once. Traditional cmos processing is still used in the process, while at the same time we now can integrate active light sources directly onto silicon." According to Zirngibl, based on the heterogeneous integration process developed by the CEA-Leti and III-V lab, III-V materials such as InP can be integrated onto silicon wafers. The fabrication process starts on 200mm silicon on insulator wafers where the silicon waveguides and modulators are fabricated on CEA-Leti 200mm cmos pilot line. "We are proud to jointly present with III-V lab the results of the integrated silicon photonics transmitter and the tunable laser," said Laurent Fulbert, Photonics Program Manager at the CEA-Leti France. "The ability to integrate a tunable laser, a modulator and passive waveguides on silicon paves the way of further developments on integrated transceivers that can address several application needs in metropolitan and access networks, servers, data centres, high performance computers as well as optical interconnects at rack level and board level. We are pleased to bring our contribution to these state of the art results which can truly revolutionise optical communications."