Funding type: COFUND Marie Slodowska Curie Action

This project is under the Marie Skłodowska-Curie Actions (MSCA) program. There are no nationality conditions but the candidates must fulfill the MSCA mobility conditions, which means that she/he must not have stayed more than 1 year in France during the last 3 years immediately before the call deadline (31/05/2019).

Expected start date: 01/10/2019

Contacts:

Ass. Prof. Christelle Monat
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+33 4 72 18 62 54

Pr. Arnan Mitchell, RMIT
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Websites:

• https://www.rmit.edu.au/about/our-locations-and-facilities/facilities/research-facilities/micronano-research-facility
• http://inl.cnrs.fr/en/

Collaborations/External partners :

Domain and scientific context :

In the past two decades, silicon photonics has emerged as a mature technological platform allowing for multiple optical functions to be integrated onto the same chip. Electro-optic modulators, SiGe photodetectors and low-loss silicon waveguides are now available. However, when it comes to light emission or nonlinear functions, silicon turns out to be intrinsically limited. The heterogeneous integration of III-V materials onto silicon has already provided a way to realize efficient LED or laser devices. Similarly, several material candidates are investigated for their nonlinear properties, with the aim to integrate them onto the mature silicon photonic platform. The nonlinear optical response of materials can sustain the realization of optical devices such as all-optical switches and even amplifiers that can directly control light signals with other light signals. These can be much faster than in their optoelectronic counterparts. Perhaps more importantly, these nonlinear properties can enable completely new functions such as wavelength conversion, the generation of frequency combs or supercontinuum pulses. More generally, a wide range of nonlinear devices can be realized for information processing using light control signals [1]. These could advantageously complement the power-hungry and bulky electronic routers that are used in telecommunications. These routers perform data processing and signal routing in the electrical domain, i.e. after converting light signals that convey information across the Internet network. They already struggle to cope with the exponentially increasing data flows across the internet, calling for the need to develop alternative and disrupting technologies. All-optical devices could play a central role there.

Keywords : 2D materials, nanophotonics, nonlinear optics, integrated optics, heterogeneous integration, phase change materials

Objectives and scientific challenges:

Despite the high application potential of nonlinear optics for all-optical information processing, no nonlinear material candidate has emerged as a clear choice to complement silicon photonics so far. On the one hand, wide band gap semiconductors have been investigated, but their integration onto silicon photonics is not straightforward. Glass materials have also been explored, but their relatively weak nonlinearity precludes the realization of compact devices. On the other hand, since the isolation of graphene, a monolayer of carbon material in 2004, several kinds of monolayer materials have emerged, offering new properties that can advantageously complement silicon photonics. Most importantly, these 2D materials can be relatively easily integrated onto planar photonic devices using post-processing techniques [2 . At RMIT, since 2017, a group of scientists have come up with a new method to synthesize 2D materials, namely from liquid metal chemistry [ 3, 4, 5, 6, 7]. This approach has turned out to provide a fruitful toolbox for producing a very wide variety of ultra-thin oxide, chalcogenide and pnictognide materials, such as HfO2, Gd2O3, GaS, GaN, Bi2Te3 and SnS among others.

The objectives of this PhD study will be (1) to explore how this new method based on liquid metals can produce 2D materials with excellent nonlinear properties and (2) to realize nonlinear optical devices by integrating these 2D materials wth more traditional semiconductor or glass based integrated optics. As a third objective, we will test these 2D materials and seek for another optical material property that is referred to as phase-change materials. This new class of materials holds the prospect for the realization of tunable/ reconfigurable optical devices and potentially non-volatile optical memories. Phase-change materials indeed present a strong optical contrast between their amorphous and crystalline states and this reversible amorphous-crystalline transition can be driven optically or electrically at high-speeds [8]. They have become popular historically as the active layer of rewriteable DVDs and are now investigated for non-volatile integrated optics applications [8 ]. However, most of the groups only focus on the GeSbTe material, which presents substantial optical losses in the near-infrared range. Exploring the potential of liquid metal chemistry for the discovery of new 2D phase-change materials would definitely widen the opportunities offered by these tunable materials.

Expected original contributions :

• Contribution to the development of new 2D materials based on liquid metal chemistry
• Investigation/ identification of the nonlinear optical properties of liquid metal based 2D materials
• Integration of these 2D materials onto chip-based devices for the realization of nonlinear optical functions
• Exploration of phase-change 2D materials for reconfigurable integrated optics

Research program and methodology :

The PhD student will be involved at all stages of the studies from the 2D material fabrication to their integration into nanophotonic devices. This will include the synthesis of 2D materials based on liquid metal chemistry, as per the approach developed at RMIT, and their transfer onto semiconductor/glass devices made by more traditional clean-room nanofabrication (nanolithography, etching) at the NANOLYON nanotechnology platform (for resonant periodic structures) and the MNRF Melbourne (for waveguide structures). The PhD student will also drive the characterization of both the 2D material (ellipsometry, reflectivity, XPS…) as well as the testing of the related optical devices using the characterization setups available at INL (both linear and nonlinear optical test-beds).

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 as well as the Centre for Advanced Electronics and Sensors (CAdES) and the Centre for Future Low Energy Electronic Technologies (FLEET) with the nanomaterials team led by Dr. Torben Daeneke on liquid metal based 2D materials. The student will benefit from INL's and RMIT’s resources and expertise in silicon photonics, non-linear optics and 2D materials, both in terms of device design and on technology and clean room manufacturing aspects for the production of the first basic demonstrators. S/he will join a team of pioneers in the field of novel 2D material synthesis techniques. The PhD student will also work closely with the INL researchers and PhD students involved in the EU project GRAPHICS, which aims at integrating graphene with nanophotonics for realizing nonlinear optical devices on a chip.

Tentative timeline for the PhD studies

Year 1: Development of 2D materials based on liquid metals (RMIT). Design of waveguide based devices using 2D materials for nonlinear optics (INL). Development of transfer methods for integrating these 2D materials onto photonic devices (RMIT/INL).

Year 2: Selection of a few 2D materials for nonlinear optics and/ or phase change properties (probed by ellipsometry). Fabrication of corresponding devices and testing. These will include waveguide based approaches as well as semi-resonant structures such as thin ridge resonators relying on TE/TM coupling, or resonant structures and Bragg mirrors. These will provide different options for promoting light-matter interaction in the 2D material.

Year 3: Realization/ characterzation of optimized devices and nonlinear demonstrators with the most promising 2D materials. Writing of the thesis.

Scientific supervision:

• Description of the supervision committee :

• Integration inside the laboratories (percentage of working time inside these laboratories) : 67% at INL, 33% at RMIT

PhD funding : Co-Fund Marie Sladowska Curie Action (MSCA) ECL/RMIT (ECLAUsion program)

Profile of the candidate :

We seek a talented and ambitious researcher with a good knowledge and a solid background in the field of solid-state physics, optics, and semiconductor devices. S/he should work towards his/her Masters/honours or Engineering degree in a field apposite to one of these areas. An experience in photonics, clean-room fabrication, material deposition or optical modeling and characterization will be strongly appreciated.
Objectives for the valorization of the research work :
The results obtained will be published in peer-reviewed journals with a high impact factor and presented at international conferences in the field (CLEO-US/Europe, SPIE photonics Europe, NLO...).

Skills that will be developed during the PhD :

The PhD work lies at the frontier between material science and nanophotonics. The student will thus develop skills related to these two highly complementary technological areas. The PhD student will thus gain experience in the "nanophotonics / nanotechnology" field, from the device design (simulation and design of optical microcomponents, FDTD-Finite difference time domain, FEMSIM-finite element method, Nonlinear Schrodinger equation), the nanofabrication of these devices in clean room environments (e-beam and optical lithography, dry and wet etching), and their characterization (using the wide range of setups - microreflectivity, Fourier optics, linear and non-linear optical characterization¬ available at INL). S/he will also acquire unique know-how on the synthesis of 2D materials based on the novel chemistry method developed at RMIT, as well as some expertise on their characterization by ellipsometry and XPS.
The highly collaborative and international environment of the project will require the student to develop, in addition to technical and scientific skills, communication, teamwork and project management skills.

Professional opportunities after the PhD:

The conceptual, scientific and technological work carried out by the PhD student on the creation of a new generation of photonic components will result in the emergence of a platform that is completely different from current technologies. An increasing number of applications arises with the advances made on 2D materials, which the PhD student will have direct experience with. Finally, the nanotechnology and computation tools used by the student during the PhD will be relevant for a high number of application fields and will allow him/her to find a job in the photonics or microelectronics industry. The future prospects for the student, at the end of his thesis, include the possibility of pursuing an academic career in a prestigious photonics laboratory or joining an industry in the microelectronics, biosensor or photonics sector.

Bibliographic references about the PhD topic :

1. S. M. Hendrickson, A. C. Foster, R. M. Camacho, and B. D. Clader, “Integrated nonlinear photonics: emerging applications and ongoing challenges” J. Opt. Soc. Am. B 31, 3193 (2014)
2. T. Gu, N. Petrone, J. F. McMillan, A. van der Zande, M. Yu, G. Q. Lo, D. L. Kwong, J. Hone and C. W. Wong, “Regenerative oscillation and four-wave mixing in graphene optoelectronics” Nature Photonics 6, 554 (2012)
3. A. Zavabeti, J. Z. Ou, B. J. Carey, N. Syed, R. Orrell-Trigg, E. L. Mayes, C. Xu, O. Kavehei, A. P. O’mullane, R. B. Kaner, K. Kalantar-zadeh, “A liquid metal reaction environment for the room-temperature synthesis of atomically thin metal oxides” Science 358, 332 (2017)
4. B. J. Carey, J. Z. Ou, R. M. Clark, K. J. Berean, A. Zavabeti, A. S. Chesman, S. P. Russo, D. W. Lau, Z. Q. Xu, Q. Bao, O. Kavehei, “Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals” Nature communications 8, 14482 (2017).
5. N. Syed, A. Zavabeti, J. Z. Ou, M. Mohiuddin, N. Pillai, B. J. Carey, B. Y. Zhang, R. S. Datta, A. Jannat, F. Haque, K. A. Messalea, C. Xu, S. P. Russo, C. F. McConville, T. Daeneke & K. Kalantar-Zadeh, “Printing two-dimensional gallium phosphate out of liquid metal” Nature Communications 9, 3618 (2018)
6. N. Syed, A. Zavabeti, K. A. Messalea, E. Della Gaspera, A. Elbourne, A. Jannat, M. Mohiuddin, B. Y. Zhang, G. Zheng, L. Wang, S. P. Russo, D. Esrafilzadeh, C. F. McConville, K. Kalantar-Zadeh, and T. Daeneke, “Wafer-Sized Ultrathin Gallium and Indium Nitride Nanosheets through the Ammonolysis of Liquid Metal Derived Oxides” J. Am. Chem. Soc. 141, 104 (2019)
7. T. Daeneke, P. Atkin, R. Orrell-Trigg, A. Zavabeti, T. Ahmed, S. Walia, M. Liu, Y. Tachibana, M. Javaid, A. D. Greentree, S. P. Russo, R. B. Kaner , and K. Kalantar-Zadeh, “Wafer-Scale Synthesis of Semiconducting SnO Monolayers from Interfacial Oxide Layers of Metallic Liquid Tin” ACS Nano 11, 10974 (2017)
8. M. Wuttig, H. Bhaskaran, & T. Taubner, “Phase-change materials for non-volatile photonic applications” Nature Photonics, 11, 465 (2017).