Thèse Etude de la Topologie dans des Réseaux Photoniques en Semiconducteurs H/F - Doctorat.Gouv.Fr

Établissement : Université Paris-Saclay GS Physique École doctorale : Ondes et Matière Laboratoire de recherche : Centre de Nanosciences et de Nanotechnologies Direction de la thèse : Jacqueline BLOCH Début de la thèse : 2026-10-01 Date limite de candidature : 2026-04-30T23:59:59 The discovery of topological phases of matter (e.g. quantum Hall effect, topological insulators...) in the 1980s has led to a profoundrevolution in solid-state physics. Recently, the extension of these exotic phases to photonic systems (e.g. photonic crystals, coupledresonators, micro-structured waveguides...) has enabled a much wider and easier exploration of topological concepts, thanks to theversatility of these synthetic platforms. The present PhD project aims at extending even further the frontiers of this field of topologicalphotonics by using cavity polaritons. Polaritons are light-matter hybride particles resulting from the strong coupling between quantumwell excitons and photons confined in a cavity. Their advantages over pure photons arise from their excitonic part that allows for: i)exploring nonlinear physics (e.g. lasing...), and ii) realizing time-reversal broken topological phases similar to the quantum Hall effectusing their response to magnetic field.
Taking advantage of the technological facilities available at C2N, our group has developed state of the art semiconductor lattices wherepolariton band structures can be engineered with well-defined topological properties. For example, honeycomb lattices (i.e. artificialgraphene) have been implemented and a garden variety of exotic phenomena emerging from the Dirac cones have been explored. Wehave recently fabricated a photonic topological insulators based on a polariton lattices and were able to perform a completespectroscopy of the eigenstates which reveals the non trivial topology of the lattice.
Building on these major achievement, the goal of this PhD research program is to explore the physics of polariton fluids in sucharchitectures of lattices with the overall objectives of discovering new and non-trivial topological properties first in the linear and then inthe non-linear regime.
The work will be divided in two main parts: an experimental one with low temperature optical spectroscopy under strong magnetic fields,and a more theoretical one to evaluate the topological properties of different lattice geometries. Over the last few years, exciton polaritons in semiconductor microcavities have triggered an increased interest due to their potentialapplications for quantum science and technologies. Thanks to their mixed exciton photon nature, very promising scenari have beenproposed to use the concept of topological physics in order to synthetic materials with potential application in photonics. Main objective: theoretical and experimental study of the physics of polariton fluids in topological lattices
Workplan:
- Eigenfunction spectroscopy in multiband topological lattices
- Observation and characterisation of topological edge states. Study of their robustness
- Observation of lasing on topological edge states and characterisation of the coherence properties
- Exploration of the role of drive and non-linearities for topology Technological processes with electron beam lithography and dry etching are developed in the C2N clean room to fabricate lattices ofcoupled resonators. Optical properties are experimentally explored making use of low temperature optical spectroscopy under strongmagnetic field. Typical experiments are: photoluminescence with real space, and reciprocal space imaging with the control of thepolarization.

We are looking for students with high level academic background, highly interested in fundamental physics and motivated in conductingphysics experiments in an optics lab. Strong knowledge in quantum optics and condensed matter physics is highly soughtafter.Computer skills would be also highly appreciated for numerical calculations and modelling the experiments (Matlab, PythonorMathematica for instance) as well as computer control of the experiments (Labview, Matlab or Python for instance).
We are looking for students with high level academic background, highly interested in fundamental physics and motivated in conductingphysics experiments in an optics lab. Strong knowledge in quantum optics and condensed matter physics is highly soughtafter.Computer skills would be also highly appreciated for numerical calculations and modelling the experiments (Matlab, PythonorMathematica for instance) as well as computer control of the experiments (Labview, Matlab or Python for instance).