ΛΙΣΤΑ ΚΟΙΝΟΠΟΙΗΣΕΩΝ ΣΤΗ ΦΙΛΟΣΟΦΙΚΗ ΣΧΟΛΗ

ΘΕΜΑ: Παρουσίαση PhD Tingge Gao

ΑΠΟΣΤΟΛΕΑΣ: Charalampos Stratigis [mailto:stratigis@xxxxxxxxxxxxxxxx]

Πρόσκληση σε Δημόσια Παρουσίαση της Διδακτορικής Διατριβής του

(Σύμφωνα με το άρθρο 12 του Ν. 2083/92)

Την Τρίτη 01 Απριλίου 2014 και ώρα 16:00 στην αίθουσα Φ2 Τμήματος Φυσικής

θα γίνει η δημόσια παρουσίαση και υποστήριξη της Διδακτορικής Διατριβής του υποψήφιου διδάκτορα του Τμήματος Επιστήμης και Τεχνολογίας Υλικών κ. Tingge Gao με θέμα:

«Manipulation of Exciton Polariton Condensates in 1D Waveguides»

«Έλεγχος Πολαριτονικών Συμπυκνωμάτων σε Μονοδιάστατους Κυματοδηγούς»

ABSTRACT

Polaritons, are hybrid states of light and electronic excitations in a semiconductor microcavitie in the strong coupling regime. In this thesis, we realize ultralow threshold polariton lasing regime under optically pumping in a high finesse planar microcavity and micropillars. Temperature dependence and transition between lasing in the strong and weak coupling regime is investigated. A monotonic increase of the polariton lasing threshold with temperature is found which is consistent with the relation for the critical density of polariton condensate in quasi-thermalization regime. Notably polariton lasing regime is found to be restricted to temperatures below 60K in GaAs microcavity system. Our study shows that polariton lasing threshold decreases with reducing pillar size due to strong lateral confinement, which favours polariton energy relaxation, thermalization and avoidance of exciton diffusion.

Utilizing 1 dimensional waveguides cut through the structure we generate polariton condensates on one end and achieve their flow along the ridge owing to high finesse of these structures. The energy blueshift due to repulsive exciton-exciton interaction in the initially created exciton reservoir is found to be responsible for launching of the condensate flow. Prototype polariton condensate transistor regime is realized by gating the condensate flow along the ridge using weak gate beam. Spin dependent switching properties of the transistor are also investigated.

The spatial control of the polariton condensate flow in 1D waveguides allows implementation of integrated optical circuits based on polaritons.

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Charalampos Stratigis

Secretariat

Dept. of Materials Science and Technology

University of Crete

P.O. Box 2208,

GR-710 03 HERAKLION, GREECE

Tel. +30 2810 394272

Fax. +30 2810 394273