Physics Department Current Events
11:30 a.m., Marshak Science Building, Room 417
Department of Electrical Engineering and Computer Science,
Massachusetts Institute of Technology, Cambridge, MA 02139, United States
Nonlinearity and Hydrodynamics in Exciton-Polariton Fluids
During the last three decades, exciton-polaritons have revealed their huge potential for the study of interacting
Bose gases in the solid state. In semiconductor microcavities, polaritons arise from the strong coupling between
quantum well excitons and cavity photons. The resulting particles are hybrid objects, composed of half-matter
and half-light. Their unique nature brings along peculiar properties such as a very light mass, integer spin,
repulsive interaction and the possibility to easily couple with light. The combination of all these properties has
triggered large interest and led to striking experimental findings such as, for example, Bose-Einstein condensa-
tion, superfluidity and optical bistability.
In the first part of the talk we will discuss the quantum hydrodynamic turbulence of a propagating polariton
gas at the breakdown of the superfluid regime. Due to time-resolved interferometric measurements we can
quantitatively assess the conditions for the nucleation of quantized vortices in both chaotic and regular regimes
and investigate the formation and stability of dark solitons.
In the second part of the talk we will discuss the nonlinear behavior and the lasing of confined polaritons. We
have investigated a new relaxation mechanism for confined polaritons which preserves nonlinearity and allows
for coherent phenomena. This mechanism involves optical bistability, phonon interaction, long polariton life-
time and bosonic stimulation. The combination of all those ingredients results in a multimode laser at different
energies able to perform all-optical spin logic operations.
Gabriele Grosso, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA