Silicon and laser: a brilliant pairing!

Researchers at Télécom ParisTech, in partnership with the University of California, Santa Barbara (UCSB), have developed new optical sources. These thermally-stable, energy-saving lasers offer promising potential for silicon photonics. These new developments offer numerous opportunities for improving very high-speed transmission systems, like datacomms and supercomputers. Their results were published in Applied Physics Letters last summer, a journal edited by AIP Publishing.

Silicon photonics is a field that is aiming to revolutionize the microelectronics industry and communication technologies. It combines two of the most significant inventions: the silicon integrated circuit and the semiconductor laser. Integrating laser functions into silicon circuits opens up a great many perspectives, allowing data to be transferred quickly over long distances compared to conventional electronic solutions, while benefiting from silicon’s large-scale production efficiency. But there’s a problem: silicon is not a good at emitting light. The laser emissions are therefore achieved using materials from column III of the famous periodic table and one element from column V, specifically, boron or gallium with arsenic or antimony.

Researchers from Télécom ParisTech and the University of California, Santa Barbara (UCSB) have recently presented a new technology for preparing these III-V components by growing them directly on silicon. This technological breakthrough enables researchers to obtain components with remarkable properties in terms of power output, power supply and thermal robustness. The results show that these sources have more stability in the presence of interfering reflections—a critical aspect in producing low-cost communication systems without an optical isolator. Industrial giants such as Nokia Bell Labs, Cisco, Apple and major digital stakeholders like Google and Facebook have high hopes for this technology. It would allow them to develop the next generation of extremely high-speed optical systems.

The approach currently used in the industry is based on thermally adhering a semiconductor laser (developed with a III-V material) to a structured silicon substrate to direct the light. Thermal adhesion does not optimize costs and is not easily replaced, since silicon and III-V elements are not naturally compatible. However, this new technology will pave the way for developing laser sources directly on silicon, a feat that is much more difficult to achieve than for other components (modulator, guides, etc.) For several years now, silicon has become an essential component in microelectronics. And these new optical sources on silicon will help the industry adapt its manufacturing processes without changing them and still respond to the current challenges: produce higher-speed systems that are cost-effective, compact and offer energy savings.

This technological breakthrough is the result of collaboration between Frédéric Grillot, a researcher at Télécom ParisTech, and John Bowers, a researcher at the UCSB. The work of Professor Bowers’ team contributed to developing technology that produced the first “hybrid III-V on silicon” laser with Intel in 2006. In 2007, it won the “ACE Award” (Annual Creativity in Electronics) for the most promising technology. The collaboration between John Bowers and Frédéric Grillot and his team is one of the few that exist outside the United States.