Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)


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Master 2 Internship - Polariton collective states and solitons in a polaritonic waveguide

par Christelle EVE - publié le

The interaction between electronic excitations (excitons) and photons is strongly enhanced in optical microcavities, compared to a bulk medium. When large enough, it can reach the strong coupling regime, where the perturbation theory isn’t suitable anymore to understand the light-matter interaction. In this regime, the new eigenstates are the so-called polaritons, half exciton/half photon quasi-particles. They can be generated, transported, accumulated in dense phases and brought into strong interactions. The discovery of the Bose condensation of polaritons in 2006 [1] (at low temperature in a GaAs microcavity) has triggered many interesting research projects and led to the discovery of the superfluidity of polariton condensates, the observation of unique kinds of vortices in these “fluids of light”, and the development of polaritonic devices.
GaN and ZnO-based microcavities have raised a large interest in the community thanks to their robust excitons and large oscillator strength. Indeed polariton condensates can be demonstrated at room temperature, which is a strikening advantage with respect to GaAs devices operated at cryogenic temperatures. Together with our colleagues from the laboratories CRHEA, C2N and IP, our group has demonstrated in 2013 the condensation of polaritons in a ZnO microcavity at 300K [2] and investigated the spatial propagation of the condensates in a standard 2D cavity [3].
The present internship is focused on a new kind of polaritonic device : the polaritonic waveguide, i.e. an optical waveguide in which propagating photons and excitons are in the strong coupling regime. The waveguide polaritons have much longer lifetimes than cavity polaritons due to the low waveguide losses, and their investigation in GaAs is quite recent [4]. Dedicated samples from CRHEA and C2N based on ZnO and GaN show that polariton lasing can be achieved in this new geometry. We plan to investigate the formation of temporal solitons in polaritonic waveguides, as well as original pattern formations inspired from the atomic physics community, at the frontier between non-linear optics and condensate physics.
The internship is funded by the ANR project “Plug-and-Bose”, gathering the C2N, CRHEA, IP and L2C laboratories. It could lead to a PhD application in the group. The candidate should have a strong background in semiconductor physics and/or quantum optics, optical spectroscopy, non-linear optics.

1. Kasprzak, J. et al. Bose-Einstein condensation of exciton polaritons. Nature 443, 409–414 (2006).
2. Li, F. et al. From Excitonic to Photonic Polariton Condensate in a ZnO-Based Microcavity. Phys Rev Lett 110, 196406– (2013).
3. Hahe, R. et al. Interplay between tightly focused excitation and ballistic propagation of polariton condensates in a ZnO microcavity. Phys. Rev. B 92, 235308 (2015).
4. Walker, P. M. et al. Ultra-low-power hybrid light–matter solitons. Nat. Commun. 6, 8317 (2015).

Supervision :
Thierry Guillet :
Christelle Brimont :