Charged InAs/GaAs quantum dots (QD) are promising candidates for quantum information processing. Entangling the spin degree of freedom of a charge confined in the QD and the polarization of single incoming photons would allow implementing deterministic spin-photon and photon-photon quantum gates. A promising strategy for this is to take advantage of the giant polarization rotations induced by a single spin, as in micropillar cavity-based spin-photon interfaces. In this way, the polarization of a photon reflected from the device changes in a spin-dependent way, encoding the spin information on the polarization degree of freedom. The goal for such an interface is to obtain a perfect mapping between the spin state and the polarization of a reflected photon. In this presentation, I explore this interaction to demonstrate, both experimentally and theoretically, a measurement back-action phenomenon  onto the spin state, upon the detection of a reflected photon in a given polarization state. By exploiting a time-resolved polarization tomography technique, we experimentally show the emergence of a spin population imbalance and/or quantum coherence upon detection of a reflected photon. We also present experimental evidence of the perfect spin-photon mapping configuration, showcasing the potential of this platform as an efficient light-matter interface.