The optical response of a heavily doped quantum well, with two occupied subbands, has been investigated as a function of the electronic density. It is shown that the two optically active transitions are mutually coupled by dipole-dipole Coulomb interaction, which strongly renormalizes their absorption amplitude. In order to demonstrate this effect, we have measured a set of optical spectra on a device in which the electronic density can be tuned by the application of a gate voltage. Our results show that the absorption spectra can be correctly described only by taking into account the Coulomb coupling between the two transitions. As a consequence, the optical dipoles originating from intersubband transitions are not independent, but rather coupled oscillators with an adjustable strength.
@article{arxiv.1301.5837,
title = {Gate controlled coupling of intersubband plasmons},
author = {Aymeric Delteil and Angela Vasanelli and Yanko Todorov and Bruno Paulillo and Giorgio Biasiol and Lucia Sorba and Carlo Sirtori},
journal= {arXiv preprint arXiv:1301.5837},
year = {2013}
}