Polaritons in micropillars: from single-photon phase shift to spin-orbit interaction in photonic graphene

Microcavities based on gallium arsenide are experimentally investigated and analysed, with polaritons in single and honeycomb micropillar geometries.

First, the single micropillar polariton energy structure is analysed. A pillar is selected with appropriate energy and phase matching conditions that satisfy parametric scattering. Parametric scattering is attempted but is not successful in our device. Pump-probe laser excitation is used to seed a final state population in the parametric scattering signal state. With appropriate incident power, stimulated scattering is seen in the idler polariton mode. The parametric blockade was the motivation for using the single micropillar device. The photon statistics of the central polariton mode were analysed, no evidence of anti-bunching was found.

The next part of this thesis uses two separate micropillar devices and explores the phase imprinted from one polariton mode onto another. The size of the phase shift is measured using a sensitive polarisation detection basis. The two devices have different exciton fractions in their respective modes, which changes the predicted and experimental phase shift, with the most significant phase value per polariton found to be 3mrad.

Finally, polaritons are confined within a period array of micropillars. The photoluminescence spectra from a honeycomb lattice have a TE-TM field akin to Dresselhaus spin-orbit coupling around the Dirac points. The pseudospin for polaritons found in non-resonant excitation is confirmed by resonantly exciting at the Dirac point energies in the S-band and P-band. The optical spin-Hall effect shows that the pseudospin pattern has two clear domains in the recorded real-space spectra.