We propose a pump-probe setup to analyze the properties of the collective excitation spectrum of a spinor polariton fluid. By using a linear response approximation scheme, we carry on a complete classification of all excitation spectra, as well as their intrinsic degree of polarization, in terms of two experimentally tunable parameters only: the mean-field polarization angle and a rescaled pump detuning. We evaluate the system response to the external probe, and show that the transmitted light can undergo a spin rotation along the dispersion for spectra that we classify as diffusivelike. We show that in this case, the spin flip predicted along the dispersion is enhanced when the system is close to a parametrically amplified instability.

• Received 4 November 2014
• Revised 22 December 2014

DOI:https://doi.org/10.1103/PhysRevB.91.075308