Evidence for parametric memory and correlation in semiconductor microcavities

TL;DR

This study investigates the delayed dynamics of polariton parametric scattering in semiconductor microcavities, revealing the importance of correlated signal-idler polariton fields and long polariton lifetimes for stimulated emission.

Contribution

It provides experimental evidence for the non-instantaneous, parametric memory effects in polariton scattering, supported by a model of coherent polariton conversion.

Findings

Delayed stimulated scattering observed with 250 fs resolution

Long polariton lifetime (~10 ps) enables correlation buildup

Model confirms coherent conversion of pump polaritons into signal-idler pairs

Abstract

We measured the dynamics of polariton parametric stimulated scattering in semiconductor microcavities, by time-resolving the amplified signal with 250 fs resolution. Our experiments demonstrate that the stimulation process is considerably delayed with respect to the arrival time of both probe and pump pulses. This effect is clearly observable in our high quality sample due to the long lifetime of the microcavity polaritons (about 10 ps), and it is in excellent agreement with the model describing the coherent conversion of two pump polaritons into a signal-idler pair. We demonstrate that the non-instantaneous character of the polariton stimulation occurs because the polariton-wave amplification requires the build up of correlated signal-idler polariton fields.