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:
Dr. Christian Grillet, CNRS/Ecole centrale de Lyon
This email address is being protected from spambots. You need JavaScript enabled to view it.
+ 33 4 72 18 62 53

Pr. Arnan Mitchell, RMIT
This email address is being protected from spambots. You need JavaScript enabled to view it.

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.).
Strongly resonant (high-quality Q factor) resonators represent an essential element in photonics, for exploring the fundamental aspects of light-matter interaction , as well as for applications in filtering, wavelength demultiplexing, sensing and, combined with an active or nonlinear material, generation of light. High-Q micro-cavities in the mid-IR have been introduced only recently  and the topic remains very challenging, in particular when integrating them with a photonic platform amenable to lasing. Such a platform would enable high-purity sources for sensitive detection in this spectral range based on heterodyne detection.  
Keywords: mid-IR, optical micro-cavities, integrated photonics, Lasers, nonlinear optics, heterogeneous integration

Scientific challenges and objectives:
Despite its recognized potential, mid-IR technologies are still limited in their range of applications. Optical systems operating in the mid-IR wavelength range have long been restricted to large, cumbersome and fragile configurations of discrete components operating in free space, potentially including simple passive waveguides, generally based on multimode chalcogenide fibres. The cost of these systems also generally prohibitive due to the lack of compact mass manufacturable mid-IR optical devices. In addition, mid-IR lacks the powerful and affordable testing and measurement tools that are available in the telecom spectral range, which makes characterisation in this spectral range more demanding.
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 resonator.

In this thesis, our objectives are:

• to develop novel design concepts for high-Q resonators based on currently exploited mid-IR photonic platforms, including SiGe alloys, LiNbO3 and high band gap SC like GaP and InP. In particular, we will pursue an original approach using multimode ring resonators to create frequency combs with tunable free spectral range (FSR).
• 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. Besides whispering gallery and racetrack resonators, photonic crystal structures will offer a huge parameter space to tailor the desired optical properties. Because of the favourable geometric scaling, these will be in principle much easier to fabricate than in the near IR, leaving much larger room for improvement which has barely been considered up to date.
The resonator will be built in a way that it will be integrated monolithically with a generic mid-IR photonic circuit, which is of paramount importance for using it as a key building block for future integrated photonic systems.
Expected original contributions include the

• First high-Q resonator 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.
• First demonstration of a frequency comb or frequency mixing exploiting multimode waveguides-based resonator.  

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 .

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 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...). 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.

Bibliographic references about the PhD topic:

1. Vahala, Kerry J. "Optical microcavities." nature 424.6950 (2003): 839.
2. Shankar, Raji, Irfan Bulu, and Marko Lončar. "Integrated high-quality factor silicon-on-sapphire ring resonators for the mid-infrared." Applied Physics Letters 102.5 (2013): 051108; Shankar, Raji, et al. "Mid-infrared photonic crystal cavities in silicon." Optics Express 19.6 (2011): 5579-5586.
3. Palaferri, Daniele, et al. "Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers." Nature 556.7699 (2018): 85.
4. Combrié, Sylvain, et al. "Comb of high‐Q Resonances in a Compact Photonic Cavity." Laser & Photonics Reviews 11.6 (2017): 1700099.