Doctorat (M/F) in photonics

Job Description

Missions

Information processing methods, whether digital or analog, are now essential for the implementation of telecommunications systems and for data analysis—particularly through the execution of static or dynamic routing functions and pattern recognition in signals or images. Frequency-Shifted Loops (FSLs), which operate on the principle of generating a large number of replicas of a given signal shifted in both time and frequency [1–3], offer an attractive solution for performing numerous high-speed analog operations, such as the Fourier transform, signal correlation, or matrix multiplication [4,5].

However, to date, the available BDF demonstrators, which make use of architectures based on optical fibers and fiber-based components, have proven to be relatively bulky. The objective of the ANR Fresh-Mint project and, by extension, of this thesis, is to evaluate the feasibility of more compact solutions avoiding the optical amplification stage, that rely on millimeter-scale, low-loss optical resonators made of lithium niobate and exploiting the electro-optic effect to implement frequency shifting function through simple serrodyne (or sawtooth) modulation.

More specifically, the proposed PhD focuses on demonstrating BDF using linear or ring resonators integrated using the thin-film lithium niobate (TFLN) technological platform. The work will address three key areas essential to this proof of concept and the development of the related components. The first part involves the modeling and design of resonators and electrodes optimized for the generation of frequency-shifted signals. The second strands concerns the development and implementation of reliable, high-performance, and reproducible microfabrication processes for these components. This fabrication step will be carried out in the LAAS cleanroom, one of the five major technology centers of the French national academic network RENATECH. This activity will benefit from the support of the cleanroom technical staff and will build on the team previously-obtained results whithin the ANR RESON project [6–8] and the NanoFiLN project of the “Electronics” PEPR [9,10]. Finally, the last task will address the performance characterization of the fabricated components. Preliminary tests will be conducted in-house to ensure that the devices are fully operational prior to a more in-depth evaluation in collaboration with the FOTON Rennes team for more advanced applications.

This PhD studentship will be hosted by the LAAS-CNRS Photonics Team, and is part of the ANR Fresh-Mint project where different FSL architectures will be assessed being based on fibre components, laser-polished millimetric disks or the above-mentioned integrated photonic solution.

[1] H. Guillet De Chatellus, O. Jacquin, O. Hugon, W. Glastre, E. Lacot, and J. Marklof, Generation of ultrahigh and tunable repetition rates in CW injection-seeded frequency-shifted feedback lasers, Opt. Express 21, 15065 (2013).
[2] H. Guillet De Chatellus, E. Lacot, W. Glastre, O. Jacquin, and O. Hugon, Theory of Talbot lasers, Phys. Rev. A 88, 033828 (2013).
[3] H. Yang, M. Brunel, M. Vallet, H. Zhang, and C. Zhao, Analysis of frequency-shifting loops in integer and fractional Talbot conditions: electro-optic versus acousto-optic modulation, J. Opt. Soc. Am. B 37, 3162 (2020).
[4] C. Schnébelin and H. Guillet De Chatellus, Agile photonic fractional Fourier transformation of optical and RF signals, Optica 4, 907 (2017).
[5] C. Schnébelin, J. Azaña, and H. Guillet De Chatellus, Programmable broadband optical field spectral shaping with megahertz resolution using a simple frequency shifting loop, Nat Commun 10, 4654 (2019).
[6] F. Renaud, A. Monmayrant, S. Calvez, O. Gauthier-Lafaye, A.-L. Fehrembach, and E. Popov, Second-harmonic-generation enhancement in cavity resonator integrated grating filters, Opt. Lett. 44, 5198 (2019).
[7] E. Hemsley, O. Gauthier-Lafaye, A. Monmayrant, P. Dubreuil, S. Calvez, A.-L. Fehrembach, and E. Popov, Critical coupling in cavity-resonant integrated-grating filters (CRIGFs), Opt. Express 31, 27274 (2023).
[8] A. Monmayrant, S. Calvez, P.-F. Calmon, P. Dubreuil, S. Charlot, A.-L. Fehrembach, E. Popov, and O. Gauthier-Lafaye, Cavity resonator-integrated guided-mode resonance filters with on-chip electro- and thermo-optic tuning, Opt. Express 30, 16669 (2022).
[9] C. Selva, K. Kinjalk, A. Monmayrant, O. Gauthier-Lafaye, and S. Calvez, Waveguide Loss Model and Geometry Optimization for Linear and Nonlinear Applications, in Integrated Photonics Platforms IV, edited by D. Van Thourhout, D. Marris-Morini, and P. O'Brien (SPIE, Strasbourg, France, 2026), p. 31.
[10] C. Selva, K. Kinjalk, A. Moreau, J. Lumeau, A.-L. Fehrembach, A. Monmayrant, O. Gauthier-Lafaye, and S. Calvez, Photonics Devices Based on Lithium Niobate On Insulator (LNOI), in (IEEE, Prague (Czech Republic), 2026).

Activity

- Design of low-loss electro-optically modulated resonators
- Microfabrication of photonic components and circuits on LNOI
- Presentation of results at project meetings, in journal articles, and at conferences.
- Characterization of photonic (guided-light) structures

Your Profil

Skills

- Hold an engineering degree or a master's degree in photonics, optics, applied solid-state physics, or electronics.
- Interest in and enthusiasm for photonic and laser technologies
- Experience or training in cleanroom microelectronics would be a plus
- Strong oral and written communication skills (French and English required) to present work during project meetings and conferences, and to write articles for scientific journals.
- Strong motivated candidate with an interest in the project, and the ability to work independently to adapt to the demands of research and develop skills in photonics related to components.
- Ability to work in a team

Applications must include a detailed resume; at least two references (people who can be contacted); and a one-page cover letter;

Your Work Environment

This PhD project focuses on the design, fabrication, and characterization of photonic components and draws primarily on the design and technological expertise of the LAAS-CNRS Photonics team. It will be conducted as part of the ANR Fresh Mint project, in collaboration with the FOTON research center in Rennes and FEMTO-ST in Besançon. The position is in a sector subject to the Protection of Scientific and Technical Potential (PPST) regulations and therefore, in accordance with these regulations, requires that your appointment be authorized by the competent authority at the Ministry of Higher Education and Research (MESR).

Constraints and risks

Since part of the work will take place in a cleanroom environment, the candidate will receive comprehensive training upon arrival at the laboratory on safety and cleanroom procedures, as well as on working with laser sources, in order to carry out the fabricated device characterization.

Compensation and benefits

Compensation

2300euros/month minimum

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions