On the dynamics of ballistic exciton-polariton condensates

Abstract

Exciton-polaritons are bosonic quasiparticles - a combination of strongly coupled photonic and excitonic modes. Polaritons inherit a light effective mass from their photonic component and strong nonlinear interactions from their excitonic component. These features permit nonequilibrium Bose-Einstein condensation of polaritons at elevated temperatures and their ballistic outflow from localized pumping spots. This thesis presents a comprehensive investigation of the interaction dynamics between polariton condensates under nonresonant excitation. A condensate, formed in the vicinity of excitonic reservoir experiences repulsion and ballistically propagates away from the excitonic potential. This behavior enables coherent coupling between spatially separated polariton condensates and facilitates the formation of propagating planar polariton waves.

Resonant excitation is the established method of creating polaritons with the desired momentum in the cavity plane. However, for the application of the on-chip technologies, scalability becomes an important requirement for the used method. This thesis presents experimental realization and supporting simulations for nonresonant planar antennae for polariton condensate. Such an element uses a nonresonant beam modified by the spatial light modulator to excite planar microlens under normal angle with respect to the microcavity. Such a design enables the generation of ballistic, coherent polariton waves directed along a chosen trajectory, representing a significant advancement in the development of reprogrammable reservoir computing devices.

Direct observation of coherence and phase transfer between ballistically coupled polariton condensates is a highly difficult task, but important for understanding of processes, undergoing in the complex systems of many condensates. Many open questions remain in the context of coherence build-up in polariton graphs. This thesis presents a comprehensive study of information propagation and perturbation robustness in ballistically coupled polariton arrays. Effects of connectivity and geometry on coherence formation in polariton graphs are studied by means of time-resolved interferometry, suggesting possible advancements in the realization of polaritonic simulators.

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Identifiers

ORCID for Denis Aristov: orcid.org/0000-0002-3129-9485

ORCID for Pavlos Lagoudakis: orcid.org/0000-0002-3557-5299

ORCID for Simone De Liberato: orcid.org/0000-0002-4851-2633

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