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 (22/05/2020).

Expected start date: 01/10/2020

Contacts:

Christian Grillet
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+33 4 72 18 62 53

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 : Thales TRT

Domain and scientific context :

The Mid-infrared (Mid-IR) wavelength range - from 3 to 15 µm - is currently experiencing a huge surge in interest for an enormous range of applications that affect almost every aspect of our society, from compact and highly sensitive biological and chemical sensors, imaging, defense and astronomy. A notable feature of the MIR is that most chemical and biological compounds that relate to our health, safety and environment have a strong spectral signature in the medium infrared. The MIR therefore offers unique opportunities for the development of technologies with a high societal (sensor applications, defence, industrial and environmental security, etc.) and fundamental impact (chemistry, biology, astrophysics, etc.).

An optical microcavity (a ring resonator, a photonic crystal cavity…) when properly designed and manufactured can store the light over a very long time and in a small volume potentially leading to high intensities and thus dramatically enhancing the light matter interaction. This is of particular relevance for exploring fundamental aspects, such as non-linear effects, light generation and sensing applications. High-Q microresonators in the mid-IR have been introduced only recently and the topic remains very challenging.

Keywords : mid-IR, optical micro-cavities, integrated photonics, Lasers, nonlinear optics, heterogeneous integration

Objectives and scientific challenges:

Despite its recognized potential, Mid-IR technologies are still limited in their range of applications, largely because of the size of the Mid-IR devices (optical components operating in this wavelength range have long been restricted to discrete components operating in free space, and to simple passive guides, generally based on multimode chalcogenide fibres) and the prohibitive costs of the instruments used due to the lack of compact Mid-IR optical devices.

Our strategy is therefore based on the development of an integrated hybrid MIR platform, involving the miniaturization of optical components and their integration on a planar substrate made of materials with remarkable optical properties (particularly in terms of transparency and non-linearities) at Mid-IR wavelengths like SiGe alloys, LiNbO3 and high band gap semiconductor (SC) like GaP and InP. The student's project will focus on one of the key building block of an integrated optical circuit, namely a high Q cavity.

In this thesis, our objectives are:

• to develop novel design concepts for high-Q cavities based on currently exploited mid-IR photonic platforms, including SiGe alloys, LiNbO3 and high band gap SC like GaP and InP,
• to integrate the resonator in a mid-IR photonic circuit,
• to implement advanced characterization tools in the mid-IR, around 3 to 5 µm and 8 to 10 µm, in particular high-resolution spectroscopy,
• to demonstrate high-Q resonators, aiming at Q = 106.
  

Expected original contributions :

A variety of novel mid-IR platforms have emerged recently and many of them are available through the RMIT and INL/LETI facilities. Hence, this PhD project will leverage the possibilities offered by these materials and fabrication methods to implement novel ideas of resonators including but not limited to thin-ridge resonators, ring resonators, photonic band gap structures. These cavities will be integrated within a photonic integrated circuit.

Expected original contributions include the

• First high-Q cavity in the in the 3 to 5 µm and 8 to 10 µm range.
• First demonstration of a Mid-IR integrated frequency comb in the 3 to 5 µm and 8 to 10 µm range.

Advanced characterization techniques will be implemented in order to perform an in-depth analysis of the circuit with spectral and spatial resolution.

Research program and methodology :

The student will be involved at all stages of the project from the design of the devices using commercial or in-house developed electromagnetic modelling tools such as FEMSIM, FDTD, Schroedinger non-linear equations, the layout (based on the process design kit –PDK- provided by RMIT), the manufacture of the devices by clean room processes via the NANOLYON nanotechnology platform and the Micro Nano Research Facility - MNRF at RMIT (nanolithography, etching) and their optical characterizations

The student will be working with the Nanophotonics, Mid-IR team at the INL ECL site led by Dr. Grillet and the InPAC group led by Prof. Arnan Mitchell in RMIT. The student will benefit from INL's, RMIT’s and Thales’ resources and expertise in integrated photonics and non-linear optics, both in terms of device design (the student will rely on INL's and RMIT’s theoretical and numerical expertise as well as the electromagnetic simulation tools available) and on technology and clean room manufacturing aspects for the production of the first basic demonstrators. The student will work closely with our industrial partner Thales on the III-V SC platform (InP, GaP) in particular to optimise these new material platform in the context of mid-IR integrated photonics (losses, high nonlinearity, etc…), and the deposition process.

The student will also work closely with Thales to setup an advanced characterization test-bed. First optical characterizations will consist of dispersion and transmission measurements performed using a swept coherent sources, e.g. tuneable Quantum Cascade Laser available at Thales. More advanced characterization will be performed using a suitable implementation of Optical Coherence Tomography.

Tentative timeline for the PhD studies

Year1: Mostly at INL & Thales.

• Design and modelling of different cavities based on the available material platforms
• Setup of advanced characterization techniques and nonlinear mid-IR test-bed in INL Lyon and Thales
• Fabrication of first resonators in the different material platforms

Year 2: Mainly at RMIT.

• Design and modelling of multimode waveguides-based resonator
• Fabrication of single and multimode resonator cavities in the MNRF at RMIT
• Exploration of electro-optic comb generation at the mid-IR
• Characterisation of the resonator cavities and investigation of the limitations on the highest achievable Q factors of the cavities

Year 3: Mainly at INL and Thales.

• Refined design and advanced characterization
• Realization/ characterization of optimized devices and nonlinear demonstrators with the most promising material platform.
• 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 (including 17% at Thales), 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, nonlinear optics, clean-room fabrication, material deposition or optical modelling and characterization will be strongly appreciated.

Objectives and 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...). No patent filing or confidentiality constraints are envisaged, but this could change (in consultation with our collaborators).

Skills that will be developed during the PhD :

The student will develop the complete range of "nanophotonics / nanotechnology" skills, from device design (simulation and design of optical microcomponents using different modelling techniques including FDTD-Finite difference time domain, BPM-Beam propagation method, FEM-finite element method, Nonlinear Schrodinger equation) and their integration into a circuit using an industry standard design framework, the manufacture of these components in clean room environments (from deposition, growth to electron beam lithography, chemical etching and dry etching), their characterization (within a complete optical bench - wafer coupling, microreflectivity, Fourier optics, non-linear characterization, pulsed laser, parametric processes - that the student will have contributed to design and deploy) and data processing.

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:

This conceptual, scientific and technological work on the creation of a new generation of mid-IR photonic components will result in the emergence of a platform that is completely different from current technologies. This platform will therefore be a milestone for new scientific and technological advances in the many fields of science and industry that can benefit from the mid-infrared. The future prospects for the student, at the end of his/her thesis, are therefore extremely rich, with the possibility of pursuing an academic career in a prestigious photonics laboratory or entering an industrial field that will be eager for the skills developed by the student.