Context and main objective
Over the past 30 years, optical communications have transformed the way we transfer information around the world. Its underlying ultra-high speed fibre-optic network now plays a critical role in our global society and economy. The Internet traffic is growing exponentially, as fueled by new broadband access technologies and services. Yet, the energy requirements for providing this bandwidth can no longer be ignored and should continue to increase along with the amounts of exchanged data. The cost, size, and energy consumption of the present electronic equipment that manages these massive data flows across the network calls for the development of disruptive routing technologies. While the use of light has proved to be the most effective way to carry data over long distances, tasks such as data treatment, storage or routing are performed in electronic routers, creating bottlenecks. More energy-efficient, compact and cooler methods are needed. One promising solution lies in moving to all-optical technologies in which the optical information would be directly processed and redirected across the network via another optical signal, i.e. without being converted back and forth into electrical signals. Such technology crucially requires the development of novel platforms, in which the light–matter interaction is dramatically increased with respect to that in fibers. This implies an appropriate choice of materials and geometries to efficiently manipulate high-speed optical signals in very compact and integrated chips. GRAPHICS will develop new solutions based on graphene/ semiconductor (III-V and SOI) hybrid integration and nanophotonic concepts that promote light matter interaction, in order to create efficient devices for high-speed manipulation of optical signals. The resulting devices will lay the foundations of a novel routing technology that can directly manage, at the heart of the network, high-speed optical data in far more compact platforms that consume less power.
Ideally, the developed technology should be compatible with CMOS processing and architectures, for enabling the convergence of optics and microelectronics. Computer chips meet with severe difficulties to keep up with increasing processing speed performance while maintaining low power consumption. Microelectronics would thus equally benefit from the development of inter- and intra-chip optical interconnects, where the advantages of optics high transfer speed, high data-handling capacity are brought down to the chip level.
While silicon photonics has led to strong advances in this context, crystalline silicon has severe limitations precluding its sole use for the applications mentioned above. GRAPHICS aims to create novel graphene/ semiconductor hybrid platforms for the generation, processing, and manipulation of fast optical signals on-chip at ~1.55µm Telecom wavelengths. Our research program will focus on two main classes of nonlinear optical devices: (1) integrated pulsed III-V/ Si microlasers capable of generating short optical pulses on a chip, and (2) all-optical signal processing devices using light to control light in a fast and efficient manner. These devices will rely on two distinct nonlinear features of graphene, i.e. its saturable absorption and its nonlinear Kerr response, respectively. In addition, the capability of electrically tuning graphene optical properties will be explored to create fundamentally flexible and reconfigurable intelligent optical devices. The resulting architectures will be the cornerstone of a novel chip-based optical routing and processing technology that underpins a variety of applications related to telecommunications, datacom, and inter-and intra-chip optical communications.
The two classes of nonlinear devices targeted in the project represent significant achievements in their own right. However, they share some scientific and technological challenges. For instance, relevant strategies must be found for enhancing the typically low interaction of light with the monolayer of carbon atoms, as needed for the device miniaturization. Here, we will combine graphene with advanced microphotonic concepts and structures capable of strongly confining light microcavities, slow light and other optimized waveguide geometries to enhance the light-graphene interaction and realize compact chip-scale devices. More fundamentally, these two classes of nonlinear devices will jointly contribute to shape the long-term vision of a fully integrated photonic platform, in which the pulsed microlaser delivers directly on-chip the optical peak power necessary to trigger all other "intelligent" devices onto the same circuit. GRAPHICS will therefore help to "draw" a novel generation of photonic integrated circuits and architectures, with graphene playing a key role, to be used for managing high-speed optical data.