Spatial distribution of an optically induced excitonic reservoir below exciton-polariton condensation threshold

TL;DR

This study investigates how optically induced excitonic reservoirs in microcavities are spatially reshaped by pump power, revealing effects like local heating and extended polariton transport, challenging the assumption of static reservoir distributions.

Contribution

It provides experimental evidence of dynamic reservoir reshaping in exciton-polariton systems, highlighting mechanisms like heating and transport effects.

Findings

Barrier width decreases with increasing pump power due to local heating.

Reservoir influences emission far from the pump spot, indicating extended polariton transport.

Reservoir distribution is dynamically reshaped by pump power, not static as previously assumed.

Abstract

Optical trapping and manipulation of microcavity exciton polaritons rely on effective potentials induced by the interaction of polaritons with a reservoir of high energy excitonic particles injected by an off-resonant optical pump. Here, we experimentally investigate possible mechanisms responsible for reshaping of these effective potentials in the low-density exciton-polariton regime. We infer the spatial distribution of the reservoir from the spatially resolved energy of exciton-polariton emission measured at zero momentum (zero kinetic energy). Power-dependent shape analysis of the potential barrier induced by a focused continuous wave laser pump shows a monotonic decrease of the barrier width with increasing excitation power, which is attributed to the local heating of the sample at the pump spot. In addition, we observe the significant influence of the reservoir on the zero-momentum emission tens of micrometers away from the laser pump spot, which is in line with the previously reported enhanced transport of high-momentum excitonic polaritons from the bottleneck region. Our work presents evidence for a complex spatial reshaping of the reservoir with the pump power, contrary to the common assumption of a static reservoir distribution fixed by the intensity profile of the pump.