Microscopic optical anisotropy of exciton-polaritons in a GaAs-based semiconductor microcavity

Exciton-polaritons in semiconductor microcavities are ideal for the study of the exciton-light interaction and its dependence on light polarization. In this work, we report on the optical response and the dependence on polarization of a polariton microcavity using microreflectance anisotropy spectroscopy ($\ensuremath{\mu}$-RAS) with a spatial resolution of $10.0\ifmmode\times\else\texttimes\fi{}10.0\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}{\mathrm{m}}^{2}$. We have found that, in contrast to optical reflection, the $\ensuremath{\mu}$-RAS spectra are quite inhomogeneous along the microcavity surface. We demonstrate the existence of microscopic local domains with differences in optical anisotropy of up to $20%$ within $100\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$. These variations are independent of the detuning between the optical and excitonic resonances, which in our sample is close to 0 meV. The $\ensuremath{\mu}$-RAS line shape can be understood by using a model based on the anisotropic strain fields induced at the interfaces of the microcavity. The model agrees quite well with the experimental results and allows us to quantify the split of the energy levels of the exciton-polariton branches induced by the local break of symmetry at the microcavity interfaces.