Kyriacos Georgiou

Kyriacos Georgiou
Argonne National Laboratory | ANL · Center for Nanoscale Materials

PhD in Physics

About

36
Publications
7,037
Reads
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518
Citations
Introduction
Kyriacos currently works at the Center for Nanoscale Materials, Argonne National Laboratory and Pritzker School of Molecular Engineering, University of Chicago as a research scholar. He does research in photonics and material physics, with a particular focus on strong light-matter interactions in nanostructure.
Additional affiliations
March 2022 - present
University of Chicago
Position
  • Research Scholar
October 2020 - March 2022
University of Cyprus
Position
  • Research Fellow
September 2020 - September 2022
The University of Sheffield
Position
  • Honorary Research Fellow
Education
October 2014 - September 2018
The University of Sheffield
Field of study
  • Physics
September 2012 - September 2013
The University of Manchester
Field of study
  • Renewable Energy and Clean Technology
September 2007 - June 2012
University of Patras
Field of study
  • Physics

Publications

Publications (36)
Article
Full-text available
Lead halide perovskite nanocrystals (NCs) are highly suitable active media for solution-processed lasers in the visible spectrum, owing to the wide tunability of their emission from blue to red via facile ion-exchange reactions. Their outstanding optical gain properties and the suppressed nonradiative recombination losses stem from their defect-tol...
Article
Full-text available
While there have been numerous reports of long‐range polariton transport at room‐temperature in organic cavities, the spatiotemporal evolution of the propagation is scarcely reported, particularly in the initial coherent sub‐ps regime, where photon and exciton wavefunctions are inextricably mixed. Hence the detailed process of coherent organic exci...
Article
We have fabricated dielectric microcavities containing the molecular dye 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (DPAVB) dispersed in a transparent polymer matrix. We show that despite the relatively broad absorption linewidth of the DPAVB, the cavities enter the strong coupling regime. We use <330 ps pulses at 355 nm from a Nd:YAG...
Preprint
Full-text available
While there have been numerous reports of long-range polariton transport at room-temperature in organic cavities, the spatio-temporal evolution of the propagation is scarcely reported, particularly in the initial coherent sub-ps regime, where photon and exciton wavefunctions are inextricably mixed. Hence the detailed process of coherent organic exc...
Article
Full-text available
We have developed a simplified approach to fabricate high-reflectivity mirrors suitable for applications in a strongly-coupled organic-semiconductor microcavity. Such mirrors are based on a small number of quarter-wave dielectric pairs deposited on top of a thick silver film that combine high reflectivity and broad reflectivity bandwidth. Using thi...
Article
Strong light–matter coupling to form exciton– and vibropolaritons is increasingly touted as a powerful tool to alter the fundamental properties of organic materials. It is proposed that these states and their facile tunability can be used to rewrite molecular potential energy landscapes and redirect photophysical pathways, with applications from ca...
Preprint
Full-text available
Strong light-matter coupling to form exciton- and vibropolaritons is increasingly touted as a powerful tool to alter the fundamental properties of organic materials. It is proposed that these states and their facile tunability can be used to rewrite molecular potential energy landscapes and redirect photophysical pathways, with applications from ca...
Article
Full-text available
Ultralong-range polariton-assisted energy transfer was achieved in a microcavity containing two J-aggregate cyanine dyes. The two dyes were separated by a distance of up to 2 μm using a polymeric spacer layer. Here, it was confirmed that hybrid middle polariton (MP) states, composed of a mixture between the cavity photon modes and the different exc...
Article
Full-text available
Non‐radiative energy transfer between spatially‐separated molecules in a microcavity can occur when an excitonic state on both molecules are strongly‐coupled to the same optical mode, forming so‐called ‘hybrid’ polaritons. Such energy transfer has previously been explored when thin‐films of different molecules are relatively closely spaced (~100 nm...
Article
Full-text available
We have fabricated organic semiconductor microcavities having an extended optical path-length (up to 2 µm) that contain J-aggregates of a cyanine dye. These structures are studied using optical-reflectivity and are found to be characterized by a series of polaritonic modes. By changing the effective oscillator strength of the dye within the cavity,...
Article
Full-text available
Two-dimensional semiconducting transition metal dichalcogenides embedded in optical microcavities in the strong exciton-photon coupling regime may lead to promising applications in spin and valley addressable polaritonic logic gates and circuits. One significant obstacle for their realization is the inherent lack of scalability associated with the...
Article
Strong coupling to the electronic or vibronic transitions of an organic semiconductor has been extensively studied in microcavity structures in which a molecular film is placed between two closely spaced mirrors. Recent experiments suggest that such strong coupling can be used to modify chemical reactions; however, the geometry of conventional micr...
Article
Full-text available
The addition of alkali metal halides to hybrid perovskite materials can significantly impact their crystallisation and hence their performance when used in solar cell devices. Previous work on the use of potassium iodide (KI) in active layers to passivate defects in triple-cation mixed-halide perovskites has been shown to enhance their luminescence...
Article
Organic semiconductors are a promising platform for ambient polaritonics. Several applications, such as polariton routers, and many-body condensed matter phenomena are currently hindered due to the ultra-short polariton lifetimes in organics. Here, we employ a single-shot dispersion imaging technique, using 4 ns long non-resonant excitation pulses,...
Preprint
Full-text available
Two-dimensional semiconducting transition metal dichalcogenides embedded in optical microcavities in the strong exciton-photon coupling regime may lead to promising applications in spin and valley addressable polaritonic logic gates and circuits. One significant obstacle for their realization is the inherent lack of scalability associated with the...
Article
Full-text available
Exciton-polaritons in 2D lattice geometries now attract considerable attention as systems in which to explore new physics. However, such structures are relatively difficult to fabricate as this can involve sophisticated milling or etching of cavity layers to create arrays of defects. Here, a straightforward technique is reported that allows rapid f...
Preprint
Full-text available
Organic semiconductors are a promising platform for ambient polaritonics. Several applications, such as polariton routers, and many-body condensed matter phenomena are currently hindered due to the ultra-short polariton lifetimes in organics. Here, we employ a single-shot dispersion imaging technique, using 4 nanosecond long non-resonant excitation...
Article
Researchers from the University of Sheffield use focused‐ion beam lithography to etch micropillars into a planar microcavity formed from two dielectric mirrors placed on either side of a fluorescent conjugated‐polymer (see article number 1900067 by David G. Lidzey and co‐workers). The photoluminescence from the micropillars is explored using a seri...
Article
Full-text available
Bose-Einstein condensates of exciton-polaritons in inorganic semiconductor microcavities are known to possess strong interparticle interactions attributed to their excitonic component. The interactions play a crucial role in the nonlinear dynamics of such systems and can be witnessed as the energy blueshifts of polariton states. However, the locali...
Article
Full-text available
Researchers have optically connected organic semiconductors and inorganic thin films to produce a light-emitting diode powered by quasi-particles that are part light and part matter. Polaritons, which form when electron–hole pairs in a semiconductor interact with photons, can be energy efficient sources of coherent light. Rahul Jayaprakash from the...
Article
Full-text available
Exciton-polaritons are quasiparticles with mixed photon and exciton character that demonstrate rich quantum phenomena, novel optoelectronic devices and the potential to modify chemical properties of materials. Organic materials are of current interest as active materials for their ability to sustain exciton-polaritons even at room temperature. Howe...
Article
The light emission from a series of micropillar microcavities containing a fluorescent, red‐emitting conjugated polymer, is explored. Cavities are fabricated by defining two dielectric mirrors either side of a polymer active region. Focused ion‐beam (FIB) lithography is then used to etch pillar structures into the planar cavity having diameters bet...
Preprint
Full-text available
We report on the origin of energy-shifts in organic polariton condensates. The localised nature of Frenkel excitons in molecular semiconductors precludes interparticle Coulomb exchange interactions -the latter being the dominant mechanism for blueshifts in inorganic semiconductor microcavities that bear Wannier-Mott excitons. We examine the contrib...
Article
We report on the origin of energy-shifts in organic polariton condensates. The localised nature of Frenkel excitons in molecular semiconductors precludes interparticle Coulomb exchange interactions -the latter being the dominant mechanism for blueshifts in inorganic semiconductor microcavities that bear Wannier-Mott excitons. We examine the contrib...
Article
Full-text available
We explore the generation of anti-Stokes fluorescence from strongly coupled organic dye microcavities following resonant ground-state excitation. We observe polariton emission along the lower polariton branch, with our results indicating that this process involves a return to the exciton reservoir and the absorption of thermal energy from molecules...
Article
Full-text available
Hybridization of two fluorescent BODIPY dyes in a microcavity is achieved by coupling different exciton transitions to the same cavity mode. We characterise the luminescence of such hybrid system following non-resonant laser excitation and show that the relative population along the different polariton branches can be controlled by changing cavity...
Article
Full-text available
David G. Lidzey, Paclos G. Lagoudakis, and co-workers demonstrate room temperature polariton condensation in the yellow part of the visible spectrum from a planar organic semiconductor microcavity containing the molecular dye BODIPY-Br in article number 1700203. Single-shot polariton dispersion imaging is exploited to observe the collapse of the en...
Article
Rapid excited-state quenching in the solid state is a widespread limitation for organic chromophores. Even when molecules are dispersed in neutral host matrices, photoluminescence quantum yields decrease sharply with increased concentration, pointing to efficient intermolecular non-radiative decay pathways that remain poorly understood. Here we stu...
Article
Full-text available
Polariton condensation in the yellow part of the visible spectrum from a planar organic semiconductor microcavity containing the molecular dye bromine-substituted boron-dipyrromethene is observed. This study provides experimental fingerprint of polariton condensation under nonresonant optical excitation, including the nonlinear dependence of the em...
Article
Full-text available
Polariton condensation in the yellow part of the visible spectrum from a planar organic semiconductor microcavity containing the molecular dye bromine-substituted boron-dipyrromethene is observed. This study provides experimental fingerprint of polariton condensation under nonresonant optical excitation, including the nonlinear dependence of the em...
Article
Full-text available
On page 1615, D. G. Lidzey and co-workers explore changes in polariton population distribution in strongly coupled microcavities containing a fluorescent molecular dye. Radiative pumping of polariton states from weakly coupled species within the cavity is identified as the dominant population mechanism. A phenomenological fitting model is developed...
Article
Full-text available
The optical properties of a series of strongly coupled microcavities containing the fluorescent molecular dye BODIPY-Br (bromine-substituted boron-dipyrromethene) dispersed into a transparent dielectric matrix are explored, with each cavity having a different exciton–photon detuning. Using temperature dependent emission, time-resolved spectroscopy,...