Researchers at Télécom ParisTech, in collaboration with the University of California at Santa Barbara (UCSB), have developed new optical sources. Low energy consumption and very stable in temperature, these lasers offer promising performance for photonics on silicon, a material that has become an essential component of microelectronics. This opens up many prospects for improvements in very high-speed transmission systems, datacoms and supercomputers. The results were published this summer in the journal Applied Physics Letters, edited by AIP Publishing.
Aon silicon photonics is a discipline that aims to revolutionize the microelectronics industry and communication technologies. It is a combination of two of the most important inventions, the silicon integrated circuit and the semiconductor laser. The integration of laser functions into silicon circuits opens up many new possibilities, as it allows rapid data transfer over longer distances compared to conventional electronics, while building on the efficiency of large-scale silicon manufacturing.
Problem: Silicon itself is not a very good light emitter. Therefore, laser emissions are rather made with materials that combine a chemical element from column III of the famous periodic table, and an element from column V. Concretely, boron or gallium with arsenic or antimony.
Researchers from Télécom ParisTech and the University of California at Santa Barbara (UCSB) have just come up with a new technology of these III-V components by direct growth on silicon. This technological prowess makes it possible to obtain components with remarkable performance in terms of output power, power supply currents and temperature robustness.
The results also show an increased stability of these sources against parasitic reflections, a crucial point for the production of low-cost communication systems without optical isolators. Industrial giants such as Nokia, Bell Labs, Cisco, Apple, but also major digital players such as Google or Facebook are pinning a lot of hope on this technology. It would enable them to develop the next generation of optical systems operating at very high speeds.
The approach currently favoured by the industry is based on the thermal bonding of a semiconductor laser (made with a III-V material) to a structured silicon substrate in order to guide the light. Thermal bonding is not cost-optimal and is not easy to replace because silicon and III-V are not naturally compatible elements.
This new technology opens the way to the realization of laser sources directly on silicon, a feat that is much more complicated to achieve than for other components (modulator, guides, etc.).
In recent years, silicon has become an essential component of microelectronics. And these new optical sources on silicon will enable the industry to adapt its manufacturing processes without changing them, while meeting the current challenges of providing higher throughput rates compatible with the challenges of reducing costs, dimensions and energy consumption.
This breakthrough is the result of a collaboration between Frédéric Grillot, a researcher at Télécom ParisTech, and John Bowers, a researcher at UCSB. The work of Professor Bowers' team is at the forefront of the development of the technology that led to the first "hybrid III-V on silicon" laser in 2006 with Intel.
This technology was recognized in 2007 by the ACE Award (Annual Creativity in Electronics) as the most promising. John Bowers' collaboration with Frédéric Grillot and his team is one of the only ones outside the United States.