Complex nanophotonic and plasmonic networks for ultrafast optical devices

Photonic technologies are playing an increasingly important role in our society with revolutionary applications ranging from optical data storage to broadband fibre internet. As electronics and nanophotonics are rapidly converging toward one hybrid nanotechnology, important open challenges arise related to the routing and control of light in integrated optoelectronic circuits. In this project, a conceptually new approach toward reconfigurable and switchable optical circuits will be developed. We choose the widely-used silicon-based nanophotonics platform. Our new approach will be enabled by the integration of photonic waveguides with chalcogenide phase-change materials that are used in rewritable DVDs. Reversible optical writing of patterns into the phase-change layer will achieve reconfigurable devices for routing of optical signals on a chip.

We will take the concept of phase-change technology to the next level by exploiting the technology for studying light transport in fundamentally new types of nanophotonic devices inspired by mesoscopic physics. We will design two-dimensional photonic layers in which light is controlled by the coherent mixing of a number of possible light paths. The reconfigurable phase-change layer will be used as a wavefront shaper to send light through such photonic layers etched in the waveguide. Subsequently, a pattern of ultrafast light pulses will be projected onto the waveguide to produce an ultrafast modulation of the independent light paths. This pattern will be used to achieve ultrafast switching devices through a new process of ultrafast demixing, which is fundamentally different from conventional switching devices. These processes will be facilitated by the dramatic enhancement of the Kerr optical nonlinearity by the chalcogenide cladding, by the use of nanoplasmonic actuators, and through design of advanced nanostructures, such as photonic graphene, thereby exploiting the analogies of light with solid-state quantum electronics.

Our studies include the use of plasmonic elements as nanoscale actuators to control the chalcogenide light modulator. Conversively, we will investigate how the hybrid plasmonic-chalcogenide networks can be used to achieve optical memristors, one of the building blocks of neural architectures. Such optical elements would be a first step toward routing of signals in a brain-like manner, which could lead to radically new modes of distribution and processing of information.

This proposal is aimed at generating impact by integrating three of the most promising emerging technologies: silicon photonics, phase-change materials, and plasmonics. We expect that combinations of these different elements will result in new types of devices. For example, the proposed chalcogenide phase-change devices can act as miniature reconfigurable circuitry. They can be directly connected to phase-change RAM memory functionalities to provide optical readout of data. Although we address here optically addressable phase-change devices, electronic read- and write-operations may be readily implemented. Plasmonics, the optical response resulting from collective oscillations of electrons in metal nanostructures, forms a natural bridge between photons and electrons. Plasmonically actuated photonic waveguides therefore hold promise for designing ultracompact devices for photon-electron integration.

The adaptation of concepts from the fields of quantum electronics and light scattering to silicon integrated photonics is motivated by scientific curiosity. These new concepts may however hold potential to generate disruptive new technology which may lead to increase in information capacity and fundamental new ways of controlling optical data, with the ultimate application of brain-inspired signal routing and processing.