PhD student in Photonics (ESR9): Two-dimensional materials for neuromorphic photonics on SOI...

Updated: 3 months ago
Job Type: FullTime
Deadline: 22 May 2020

We seek a highly talented and ambitious PhD student to join, in the framework of the ECLAUSion cotutelle program (see below), our project aiming at two-dimensional materials for neuromorphic photonics on SOI platform.

The rise of the field of Silicon Photonics (SiPh) in the last decades has been heavily supported by the need to move ever-growing amount of data more efficiently and faster. In particular, the leveraging of CMOS-compatible platforms has allowed to provide SiPh solutions, which were technologically already achievable thanks to the infrastructure built by the microelectronics industry. However, this opportunity meant also that the vast majority of the solutions investigated were technologically limited to what was readily available in the foundries.

Recently, proposed SiPh solutions are starting to exploit novel technological approaches, often hybrid, to still leverage the benefits from the microelectronics industry, but with the addition of key functionalities. In particular, the field of optical signal processing is constantly seeking solutions that are more and more integrated for scalability. However, integrated solutions in SiPh platforms for applications such as photonic neuromorphic computing, which heavily rely on network reconfigurability properties, present some drawbacks. In fact, key photonic devices exploiting e.g. memory effects for such applications have several limitations (e.g. short cavity lifetime, large footprint) in standard intrinsic Silicon-On-Insulator (SOI) platforms for telecom applications. Hence, the scientific interest of exploring hybrid integration of functional materials, the emerging 2D materials in particular, onto silicon photonics platform to compensate the drawbacks of pure Si will lead to the fully functional neuromorphic photonics for high-end computing on mature silicon photonics platform.

Researchers have successfully demonstrated photonic computing either by using thermal-optical effect or traditional phase changing materials on purely SiPh platforms. For the usage of thermal-optical effect, the advantage is that it can be easily programmed by using advanced microelectronic circuits, while the disadvantage is the power budget, as the weights for optical analog computing on PICs are adjusted by local heating of the waveguides, and this requires surprisingly large amounts of energy to tune the weights. On the other hand, the usage of traditional phase changing materials does not require high power operation as they can be modulated by using pulsed light, but the disadvantage is very obvious: the controlling by external light illumination is challenging on-chip which limits its integration density. Therefore, one would think if there is a way to combine the electrical and optical ways together, it would be great to lead to higher density integration with low power budget neuromorphic computing devices on-chip.

An attractive strategy is to hybrid integrate silicon photonic devices with novel functional materials whose dielectric properties can be varied by using of low or zero power consumption. The research group at RMIT University has discovered that a new group of two-dimensional (2D) materials, exhibiting plasmonic behaviours, are emerging, and their plasmon resonance wavelength and intensity can be controlled by the concentrations of ionic dopants and concurrently injected free charge carriers. The most recent investigation demonstrated that by using external voltage on the pre-doped 2D materials, the charges in the materials will be re-distributed, which will lead to the plasmonic property change dramatically. Most importantly, such voltage tuning does not need current as the static electrical field is enough to separate the positive and negative charges in the materials. So, one can say that the materials can be tuned by electrical method without power consumption. Using this approach, it is possible to create programmable and reconfigurable optical circuits with low power requirements to enable future information processing systems on silicon photonics platform.

The objectives of this PhD study will be (1) to identify the system requirements for neuromorphic computing on a photonic chip harnessing the existing building blocks and identifying any missing building blocks or bottlenecks that could be the focus of further research; (2) work with the research teams at RMIT to design and realize a suite of demonstrator circuits and characterize these as record breaking neuromorphic computing elements; (3) explore the opportunity for 2D plasmonic materials integrated on silicon photonics platform to realize non-volatile low-power photonic chip reconfiguration. In particular, this platform could provide a considerable improvement in terms of power consumption over other systems because of the very low switching power required for such memory-dependent components. Besides, non-linear effects provided by the 2D plasmonic materials will be harnessed to increase the computational performance of the neural networks.

Expected original contributions :

  • Pioneering design and demonstration of photonic chip platforms for neuromorphic computing applications using the silicon photonics platform
  • Exploration of a new non-volatile programmable circuit element by using novel 2D plasmonic materials
  • Advancement of building blocks to increase scalability, switching/writing speed and power consumption
  • Creation of some of the first photonic chip architectures leveraging these novel building blocks and experimental demonstration of initial prototypes.

Research program and methodology :

The PhD student will be involved in all the different research aspects concerning the material synthesis and characterizations, the design, fabrication and characterization of building blocks and initial prototypes. In particular, S/he will carry out design work of photonic system architectures at INL. The student will first be trained in using the integrated photonic design framework (IPKISS by Luceda Photonics) used by RMIT University and enhanced to accommodate SOI and using both commercial and custom system and device level tools. In particular, system designs will harness an event-based simulator to design architectures has been recently developed at INL for stochastic computing using phase-change materials, which could be adapted to the SOI platform and the IPKISS integrated REME (simulation tool), which is uniquely capable of designing devices in the SOI platform. While at INL, the student will design a number of simple circuits and will coordinate with the RMIT team in Australia to have these circuits realized and delivered to INL for characterization using an electro-optic test setup

The second year will be spent at RMIT learning how designs are converted into practical chips with the opportunity to learn materials synthesis and characterization, devices fabrication and packaging skills. They will particularly use this time to explore enhanced circuit elements including non-volatile programmable elements that can be used for more sophisticated information processing circuits.

In the final year, the student will return to INL with the second generation of photonic circuits and will conduct record breaking demonstrations with these chips. The final year will present the opportunity for a third iteration, pushing the boundaries of system complexity realizing the vision of programmable system design initiated in the first year and incorporating the insights into practicalities and opportunities of device and system realization gained in the second year. This will enable a final breakthrough demonstration that will complete the PhD.

The student will be working with the Nanophotonics research group at INL hosted by Ecole Centrale de Lyon, the Integrated Photonics and Applications Centre (InPAC) by Prof. Arnan Mitchell at RMIT for integrated photonic devices and the nanomaterials research group led by A/Prof. Jian Zhen Ou at RMIT University. The student will benefit from INL's and RMIT’s resources and photonics and materials expertise, both in terms of device/system design and on technology and clean-room manufacturing aspects for the production of the first basic prototypes. S/he will join a team of pioneers in the field of integrated photonics, materials engineering and emerging technologies for computing applications.

The cotutelle ECLAUSion program

We seek talented and ambitious PhD students to join our new cotutelle PhD program ECLAUSion. ECLAUSion will build on ECL and RMIT outstanding reputation of research excellence, state of the art research facility in micro-nanofabrication and nanotechnology platform, and the rich Lyon and Melbourne area ecosystem in biotechnology and ICT industries to offer a multidisciplinary, cutting edge research program initially centered around 4 topics impacted by nanotechnologies i) functional materials, ii) electronics and computing architecture, iii) photonics and photovoltaics, iv) biotechnology and healthcare. ECLAUSion, with their strong academic researchers, programs and industrial support for the first time gathered within a single flag, provides a unique opportunity to develop global (across continents) crossdisciplinary PhD training & research with impact ranging from fundamental science to original technological innovation underpinned by nanotechnology. The domains of application cover key economic sectors for investment and growth and have been flagged as research collaboration priority in the Australian-EU S&T roadmap: semiconductors, microelectronics and photonics, telecommunications, ICTs in general, energy, health and well-being, biosensors.

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