High resolution coherent spectroscopy of a polariton fluid : Bogoliubov modes, non equilibrium phase transitions and turbulence
Ferdinand Claude
Excitons-polaritons of semiconductor microcavities are quasiparticles originating from the dressing of optical cavity photons by the interactions between quantum well electron-hole pairs. In planar geometry, their belonging to the family of quantum fluids has been many times demonstrated through the observation of macroscopic coherence phenomena, such as superfluidity and Bose-Einstein condensation. Like ultracold atoms, polaritons support on their surface a set of collective excitations, the Bogoliubov modes, whose spectrum encompasses the key information to describe the dynamics of quantum fluids. In this thesis, we present a wide variety of results concerning the detection and control of such modes in different configurations. Thanks to the development of a new high-resolution coherent spectroscopy method, we carried out a detailed study of the spectrum of polariton collective excitations. In particular, we highlighted the effects of the driven-dissipative nature of the system on the fundamental dynamics of the fluid, by investigating the interplay between the Bogoliubov modes and the polariton bistability under coherent pumping. This was the opportunity to reveal, in addition to the well-known phonon-type excitations, precursors of dynamical instability and the so-called ghost branch. Moreover, we studied the behavior of out-of-equilibrium phase transitions: first, via the effect of the system dimension on the bistability and, second, with the onset of a Goldstone mode, as a result of a spontaneous symmetry breaking in a parametric oscillation regime. Finally, we designed a pumping geometry that directly controls the instability modes between dark solitons of a pair guided by an intensity channel, leading to the formation of vortex-antivortex streets in the density.
•Nov 28, 2022•1 citation