Friday, March 30, 2012

Integrated transmitter on silicon



The HELIOS partners demonstrated an integrated tunable transmitter on silicon. For the first time, a tunable laser source has been integrated on silicon, which represents a key milestone towards fully integrated transceivers

The transmitter incorporates a hybrid III-V/Si laser-fabricated by direct bonding, which exhibits 9 nm wavelength tunability and a silicon Mach-Zehnder modulator with high extinction ratio (up to 10 dB), leading to an excellent bit-error-rate performance at 10 Gb/s.

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 (SOI) wafers where the silicon waveguides and modulators are fabricated on CEA-Leti 200mm CMOS pilot line. Then, InP heterostructures are directly bonded to the SOI wafer, followed by the laser processing. Finally, metallization steps are performed for contacting the modulators, the heaters above ring resonators and the hybrid III-V/Si lasers.

The laser itself exhibits a maximum output power around 6.5 mW at 20°C, and still higher than 1 mW at 60°C. A single mode operation with SMSR larger than 35 dB is achieved. By thermally tuning the ring resonator placed inside the laser cavity, we achieved a tuning range of 7 nm.

The silicon modulator is a depletion type lateral pn junction modulator. For a reverse bias of 4 V, the 3 dB modulation bandwidth is around 13 GHz, and the 4 dB bandwidth is around 25 GHz.

Bit Error Rate (BER) measurements have been made at 10 Gb/s using a peuso-random binary sequence (PRBS) of a length of 27 – 1. At different wavelengths, we can achieve error free operation with BER < 10-9 with open eye diagrams for all those channels. The extinction ratio of all those wavelengths varies from 6 to 10 dB.

 
CEA (Atomic Energy Commission) is a French Governmental Research Organisation (15000 employees) devoted to both fundamental and industrial R&D. CEA-LETI is one of the major European research centres for applied electronics. More than 85% of its activity is dedicated to research finalised with external partners. Nearly 1,600 men and women are serving innovation and the transfer of technology in key domains. As the preferred contact of the industrial world, CEA-LETI has sparked the creation of nearly thirty high-technology start-ups, including Soitec, world leader in silicon on insulator

CEA-Leti is located in Grenoble where it benefits from 11000 m² state-of-the-art clean rooms, up to 300 mm wafer size, with equipment worth some 200 M€ (40 M€ are invested each year to maintain the equipment park). The yearly CEA-Leti budget was 174 M€ in 2006. L├ęti is one of the main groups behind Minatec, Europe’s main Centre of Excellence in Micro- and Nano-technology, that brings together more than 4,000 research, industry and education partners in Grenoble. CEA-LETI benefits from platforms within Minatec which group expertise and resources found nowhere else in Europe, such as the 300 mm silicon technology platform, the 200 mm microelectronics platform, the 200 mm MEMS200 microsystems platform, the nanocharacterisation platform, the Upstream platform and the Design platform.


Activities within HELIOS

“Photonics on CMOS” is one the emerging programs with already important achievements obtained with French laboratories under French Research minister contracts. CEA/LETI was involved in the IST project PICMOS. CEA will use the 200mm fabrication facility for the fabrication of all the devices.

CEA-LETI will be the HELIOS project leader, i.e. it will: drive project and ensure the respect of the timing, the milestones and deliverables.

CEA-LETI is involved in the development of major building blocks (sources, modulators, detectors), process integration, fabrication of demonstrators.
Further information

For further information about HELIOS, please contact:

Laurent Fulbert: +33 438 78 38 45 (laurent.fulbert[at]cea.fr)

Jean-Marc Fedeli: +33 438 78 68 79 (jean-marc.fedeli[at]cea.fr)

CEA-LETI website : www.leti.fr

CEA website: www.cea.fr

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