Nanoscale optomechanical interactions in semiconductor microcavities

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Microcavity exciton polaritons (to be denoted as polaritons) are bosonic matter-wave excitations resulting from the strong coupling between quantum well (QW) excitons and photons in a semiconductor microcavity (MC). Polaritons thus combine the long spatial coherence of photons with strong inter-particle interactions resulting from the excitonic component. The low effective mass together with the bosonic character enables the formation of polariton condensates with long spatial (tens of m) and time (100’s of ps) coherences at relatively low particle densities and high temperatures (i.e., liquid He temperatures for (Al,Ga)As structures). The objective of the present project is to investigate the resonant acousto-optical interaction between polaritons (and their condensates) and longitudinal acoustic phonons (denoted as gAPs) guided along the spacer layer of a structured polariton MC. We will develop a new platform for polariton-phonon coupling, which enables the simultaneous confinement of a high density of polaritons and phonons at the same spatial location. In this platform, the spectrally narrow polariton resonances (in particular, in the condensation regime) will enable the detection of gAP effects with high sensitivity. The platform will be used for accessing two complementary aspects of the resonant acousto-optical interactions. The first explores the modulation of polaritons by GHz gAPs for the formation of dynamic polariton lattices. These tunable lattices can be regarded as solid-state analogs to optical lattices of cold atoms. The polariton-phonon platform supporting high frequency (several GHz) and sub-micrometer wavelengths phonons will provide access to a regime of small spatial and time modulation periods, not possible in existing modulation schemes. The second aspect of the project will take advantage of the strong acousto-optic back-action induced by the high polariton density to control the generation, propagation, and guiding of gAPs in structured MCs.