Quantum Correlated Polariton Modes in a Semiconductor Vertical Triple Microcavity

This paper presents a semiconductor vertical triple microcavity system consisting of a MBE grown structure, made of three AlGaAs/GaAs lambda-microcavities, including single InGaAs quantum wells. The work investigated an experimental configuration expected to be optimal for generating correlated polariton modes: the pump is at 0deg, resonant with the second branch, and the signal and idler modes are at the same energy and opposite angles on the low energy branch. With this excitation geometry, a high symmetry between signal and idler modes is achieved (same photon content and same linewidth) which ensure maximal correlations. Moreover, the fact that the pump is at normal incidence allows eliminating spurious uncorrelated background noise contributions coming from the resonant Rayleigh scattering of the pump mode. Results show that in the strong light-matter coupling regime (temperature of 4 K, pump excitation 20 mW), the noise spectrum of the difference reveals 5% squeezing, demonstrating the first generation of quantum correlated polariton modes.