Inverse-phase Rabi oscillations in semiconductor microcavities

TL;DR

This study experimentally observes and explains opposite-phase Rabi oscillations between polariton modes in semiconductor microcavities, revealing fundamental quantum beat behavior of coupled light-matter states.

Contribution

It provides the first experimental observation of opposite-phase Rabi oscillations and explains their origin through pump-induced modifications of polariton Hopfield coefficients.

Findings

Opposite-phase oscillations observed at polariton modes.

Theoretical explanation links oscillations to Hopfield coefficient modifications.

Contrast with in-phase oscillations in pure excitonic states.

Abstract

We study experimentally the oscillations of a non stationary transient signal of a semiconductor microcavity with embedded InGaAs quantum wells. The oscillations occur as a result of quantum beats between the upper and lower polariton modes due to the strong exciton-photon coupling in the microcavity sample (Rabi oscillations). The registration of spectrally resolved signal has allowed for separate observation of oscillations at the eigenfrequencies of two polariton modes. Surprisingly, the observed oscillations measured at the lower and upper polariton modes have opposite phases. We demonstrate theoretically that the opposite-phase oscillations are caused by the pump-induced modification of polariton Hopfield coefficients, which govern the ratio of exciton and photon components in each of the polartion modes. Such a behaviour is a fundamental feature of the quantum beats of coupled light-matter states. In contrast, the reference pump-probe experiment performed for the pure excitonic states in a quantum well heterostructure with no microcavity revealed the in-phase oscillations of the pump-probe signals measured at different excitonic levels.