Exciton coherence propagation measured with non-local four-wave mixing micro-spectroscopy

Raczyński, M., Dydniański, A., Połczyńska, K. E., Szwed, G., Szczerba, A., Jung, J.-W., Nogues, G., Langbein, W. ORCID: https://orcid.org/0000-0001-9786-1023, Kossacki, P., Pacuski, W. and Kasprzak, J. 2026. Exciton coherence propagation measured with non-local four-wave mixing micro-spectroscopy. Optica 13 (2) , pp. 362-365. 10.1364/optica.582443

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Abstract

Coherence transfer is a multi-disciplinary topic of interest, including chemistry, biology, and physics. In quantum technologies, achieving non-local coherent coupling between solid-state qubits is of the utmost importance. Here, we demonstrate that excitons—i.e., electron–hole pairs bound by the Coulomb force within a quantum well—can act as a medium for mesoscopic optical coherence transfer in semiconductors. To this end, we use a femtosecond laser pulse to resonantly generate excitons within the light cone. These excitons can then either recombine radiatively or scatter out of the light cone, gaining an in-plane momentum in the process. In samples without disorder, such as the CdTe quantum wells used here, the resulting fast excitons can diffuse over mesoscopic distances before recombining radiatively. Using coherent nonlinear micro-spectroscopy, we carry out exciton time-of-flight measurements. Specifically, we monitor the spatio-temporal propagation of launched exciton wave packets, selectively observing their coherence or density on a scale of up to 10 µm. Our proof-of-principle experiment demonstrates that free excitons inherit a phase modulation from the optical pulsed excitation and can generate coherent links within excitonic circuits, offering a higher level of miniaturisation and compactness than photonic or polaritonic architectures.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2026-02-20
Publisher:	Optica Publishing Group
Date of First Compliant Deposit:	3 March 2026
Date of Acceptance:	10 January 2026
Last Modified:	03 Mar 2026 15:15
URI:	https://orca.cardiff.ac.uk/id/eprint/185438

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