Terahertz excitation of a coherent three-level {\Lambda}-type exciton-polariton microcavity mode

TL;DR

This study demonstrates terahertz pulses can coherently excite a three-level system in a microcavity, revealing strong coupling effects and nonlinearities in exciton-polariton states and the 2p-exciton state.

Contribution

It introduces a novel three-level mbda-type system involving exciton-polariton modes and the 2p-exciton state in a microcavity, with detailed microscopic theoretical explanation.

Findings

Terahertz pulses strongly couple polariton states to the 2p-exciton state.

Pronounced nonlinearities observed via time-resolved spectroscopy.

No resonant transition observed between the two polariton levels.

Abstract

Interactions of few-cycle terahertz pulses with the induced optical polarization in a quantum-well microcavity reveal that the lower and higher exciton-polariton modes together with the optically forbidden 2p-exciton state form a unique {\Lambda}-type three-level system. Pronounced nonlinearities are observed via time-resolved strong-terahertz and weak-optical excitation spectroscopy and explained with a fully microscopic theory. The results show that the terahertz pulses strongly couple the exciton-polariton states to the 2p-exciton state while no resonant transition between the two polariton levels is observed.