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Menghrajani KS, Vasista AB, Tan WJ, Thomas PA, Herrera F, Barnes WL. Molecular Strong Coupling and Cavity Finesse. J Phys Chem Lett 2024; 15:7449-7457. [PMID: 39008808 DOI: 10.1021/acs.jpclett.4c00782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/17/2024]
Abstract
Molecular strong coupling offers exciting prospects in physics, chemistry, and materials science. While attention has been focused on developing realistic models for the molecular systems, the important role played by the entire photonic mode structure of the optical cavities has been less explored. We show that the effectiveness of molecular strong coupling may be critically dependent on cavity finesse. Specifically we only see emission associated with a dispersive lower polariton for cavities with sufficient finesse. By developing an analytical model of cavity photoluminescence in a multimode structure we clarify the role of finite-finesse in polariton formation and show that lowering the finesse reduces the extent of the mixing of light and matter in polariton states. We suggest that the detailed nature of the photonic modes supported by a cavity will be as important in developing a coherent framework for molecular strong coupling as the inclusion of realistic molecular models.
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Affiliation(s)
- Kishan S Menghrajani
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Adarsh B Vasista
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Wai Jue Tan
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Philip A Thomas
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Felipe Herrera
- Department of Physics, Universidad de Santiago de Chile, Av. Victor Jara 3493, Santiago 9170124, Chile
- Millennium Institute for Research in Optics, Concepción 750, Chile
| | - William L Barnes
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
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2
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Thomas PA, Tan WJ, Kravets VG, Grigorenko AN, Barnes WL. Non-Polaritonic Effects in Cavity-Modified Photochemistry. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2309393. [PMID: 37997481 DOI: 10.1002/adma.202309393] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 10/23/2023] [Indexed: 11/25/2023]
Abstract
Strong coupling of molecules to vacuum fields is widely reported to lead to modified chemical properties such as reaction rates. However, some recent attempts to reproduce infrared strong coupling results have not been successful, suggesting that factors other than strong coupling may sometimes be involved. In the first vacuum-modified chemistry experiment, changes to a molecular photoisomerization process in the ultraviolet-visible spectral range are attributed to strong coupling of the molecules to visible light. Here, this process is re-examined, finding significant variations in photoisomerization rates consistent with the original work. However, there is no evidence that these changes need to be attributed to strong coupling. Instead, it is suggested that the photoisomerization rates involved are most strongly influenced by the absorption of ultraviolet radiation in the cavity. These results indicate that care must be taken to rule out non-polaritonic effects before invoking strong coupling to explain any changes of properties arising in cavity-based experiments.
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Affiliation(s)
- Philip A Thomas
- Department of Physics and Astronomy, University of Exeter, Exeter, EX4 4QL, UK
| | - Wai Jue Tan
- Department of Physics and Astronomy, University of Exeter, Exeter, EX4 4QL, UK
| | - Vasyl G Kravets
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | | | - William L Barnes
- Department of Physics and Astronomy, University of Exeter, Exeter, EX4 4QL, UK
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3
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Georgiou K, Athanasiou M, Jayaprakash R, Lidzey DG, Itskos G, Othonos A. Strong coupling in mechanically flexible free-standing organic membranes. J Chem Phys 2023; 159:234303. [PMID: 38112504 DOI: 10.1063/5.0178144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 11/22/2023] [Indexed: 12/21/2023] Open
Abstract
Strong coupling of a confined optical field to the excitonic or vibronic transitions of a molecular material results in the formation of new hybrid states called polaritons. Such effects have been extensively studied in Fabry-Pèrot microcavity structures where an organic material is placed between two highly reflective mirrors. Recently, theoretical and experimental evidence has suggested that strong coupling can be used to modify chemical reactivity as well as molecular photophysical functionalities. However, the geometry of conventional microcavity structures limits the ability of molecules "encapsulated" in a cavity to interact with their local environment. Here, we fabricate mirrorless organic membranes that utilize the refractive index contrast between the organic active material and its surrounding medium to confine an optical field with Q-factor values up to 33. Using angle-resolved white light reflectivity measurements, we confirm that our structures operate in the strong coupling regime, with Rabi-splitting energies between 60 and 80 meV in the different structures studied. The experimental results are matched by transfer matrix and coupled oscillator models that simulate the various polariton states of the free standing membranes. Our work demonstrates that mechanically flexible and easy-to-fabricate free standing membranes can support strong light-matter coupling, making such simple and versatile structures highly promising for a range of polariton applications.
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Affiliation(s)
- Kyriacos Georgiou
- Department of Physics, Laboratory of Ultrafast Science, University of Cyprus, Nicosia 1678, Cyprus
| | - Modestos Athanasiou
- Department of Physics, Experimental Condensed Matter Physics Laboratory, University of Cyprus, Nicosia 1678, Cyprus
| | - Rahul Jayaprakash
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - David G Lidzey
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - Grigorios Itskos
- Department of Physics, Experimental Condensed Matter Physics Laboratory, University of Cyprus, Nicosia 1678, Cyprus
| | - Andreas Othonos
- Department of Physics, Laboratory of Ultrafast Science, University of Cyprus, Nicosia 1678, Cyprus
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Bhuyan R, Mony J, Kotov O, Castellanos GW, Gómez Rivas J, Shegai TO, Börjesson K. The Rise and Current Status of Polaritonic Photochemistry and Photophysics. Chem Rev 2023; 123:10877-10919. [PMID: 37683254 PMCID: PMC10540218 DOI: 10.1021/acs.chemrev.2c00895] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Indexed: 09/10/2023]
Abstract
The interaction between molecular electronic transitions and electromagnetic fields can be enlarged to the point where distinct hybrid light-matter states, polaritons, emerge. The photonic contribution to these states results in increased complexity as well as an opening to modify the photophysics and photochemistry beyond what normally can be seen in organic molecules. It is today evident that polaritons offer opportunities for molecular photochemistry and photophysics, which has caused an ever-rising interest in the field. Focusing on the experimental landmarks, this review takes its reader from the advent of the field of polaritonic chemistry, over the split into polariton chemistry and photochemistry, to present day status within polaritonic photochemistry and photophysics. To introduce the field, the review starts with a general description of light-matter interactions, how to enhance these, and what characterizes the coupling strength. Then the photochemistry and photophysics of strongly coupled systems using Fabry-Perot and plasmonic cavities are described. This is followed by a description of room-temperature Bose-Einstein condensation/polariton lasing in polaritonic systems. The review ends with a discussion on the benefits, limitations, and future developments of strong exciton-photon coupling using organic molecules.
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Affiliation(s)
- Rahul Bhuyan
- Department
of Chemistry and Molecular Biology, University
of Gothenburg, 412 96 Göteborg, Sweden
| | - Jürgen Mony
- Department
of Chemistry and Molecular Biology, University
of Gothenburg, 412 96 Göteborg, Sweden
| | - Oleg Kotov
- Department
of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
| | - Gabriel W. Castellanos
- Department
of Applied Physics and Science Education, Eindhoven Hendrik Casimir
Institute and Institute for Complex Molecular Systems, Eindhoven University of Technology, 5612 AE Eindhoven, The Netherlands
| | - Jaime Gómez Rivas
- Department
of Applied Physics and Science Education, Eindhoven Hendrik Casimir
Institute and Institute for Complex Molecular Systems, Eindhoven University of Technology, 5612 AE Eindhoven, The Netherlands
| | - Timur O. Shegai
- Department
of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
| | - Karl Börjesson
- Department
of Chemistry and Molecular Biology, University
of Gothenburg, 412 96 Göteborg, Sweden
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Tan WJ, Thomas PA, Barnes WL. Origin of an Anticrossing between a Leaky Photonic Mode and an Epsilon-Near-Zero Point of Silver. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:19262-19267. [PMID: 36425000 PMCID: PMC9677423 DOI: 10.1021/acs.jpcc.2c05836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 10/10/2022] [Indexed: 06/16/2023]
Abstract
Strong light-matter coupling hybridizes light and matter to form states known as polaritons, which give rise to a characteristic anticrossing signature in dispersion plots. Here, we identify conditions under which an anticrossing can occur in the absence of strong coupling. We study planar silver/dielectric structures and find that, around the epsilon-near-zero point in silver, the impedance matching between the silver and dielectric layers gives rise to an anticrossing. Our work shows that care must be taken to ensure that anticrossing arising from impedance matching is not misattributed to strong coupling.
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Nagarajan K, Thomas A, Ebbesen TW. Chemistry under Vibrational Strong Coupling. J Am Chem Soc 2021; 143:16877-16889. [PMID: 34609858 DOI: 10.1021/jacs.1c07420] [Citation(s) in RCA: 80] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Over the past decade, the possibility of manipulating chemistry and material properties using hybrid light-matter states has stimulated considerable interest. Hybrid light-matter states can be generated by placing molecules in an optical cavity that is resonant with a molecular transition. Importantly, the hybridization occurs even in the dark because the coupling process involves the zero-point fluctuations of the optical mode (a.k.a. vacuum field) and the molecular transition. In other words, unlike photochemistry, no real photon is required to induce this strong coupling phenomenon. Strong coupling in general, but vibrational strong coupling (VSC) in particular, offers exciting possibilities for molecular and, more generally, material science. Not only is it a new tool to control chemical reactivity, but it also gives insight into which vibrations are involved in a reaction. This Perspective gives the underlying fundamentals of light-matter strong coupling, including a mini-tutorial on the practical issues to achieve VSC. Recent advancements in "vibro-polaritonic chemistry" and related topics are presented along with the challenges for this exciting new field.
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Affiliation(s)
- Kalaivanan Nagarajan
- University of Strasbourg, CNRS, ISIS & icFRC, 8 allée Gaspard Monge, 67000 Strasbourg, France
| | - Anoop Thomas
- Department of Inorganic & Physical Chemistry, Indian Institute of Science, Bengaluru 560012, India
| | - Thomas W Ebbesen
- University of Strasbourg, CNRS, ISIS & icFRC, 8 allée Gaspard Monge, 67000 Strasbourg, France
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Thomas PA, Menghrajani KS, Barnes WL. Cavity-Free Ultrastrong Light-Matter Coupling. J Phys Chem Lett 2021; 12:6914-6918. [PMID: 34280306 PMCID: PMC8327311 DOI: 10.1021/acs.jpclett.1c01695] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 07/02/2021] [Indexed: 05/10/2023]
Abstract
Strong coupling between light and matter can occur when the interaction strength between a confined electromagnetic field and a molecular resonance exceeds the losses to the environment, leading to the formation of hybrid light-matter states known as polaritons. Ultrastrong coupling occurs when the coupling strength becomes comparable to the transition energy of the system. It is widely assumed that the confined electromagnetic fields necessary for strong coupling to organic molecules can only be achieved with external structures such as Fabry-Pérot resonators, plasmonic nanostructures, or dielectric resonators. Here we show experimentally that such structures are unnecessary and that a simple dielectric film of dye molecules supports sufficiently modified vacuum electromagnetic fields to enable room-temperature ultrastrong light-matter coupling. Our results may be of use in the design of experiments to probe polaritonic chemistry and suggest that polaritonic states are perhaps easier to realize than previously thought.
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Affiliation(s)
- Philip A. Thomas
- Department of Physics and
Astronomy, University of Exeter, Exeter, EX4 4QL, United Kingdom
| | - Kishan S. Menghrajani
- Department of Physics and
Astronomy, University of Exeter, Exeter, EX4 4QL, United Kingdom
| | - William L. Barnes
- Department of Physics and
Astronomy, University of Exeter, Exeter, EX4 4QL, United Kingdom
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Georgiou K, McGhee KE, Jayaprakash R, Lidzey DG. Observation of photon-mode decoupling in a strongly coupled multimode microcavity. J Chem Phys 2021; 154:124309. [PMID: 33810682 DOI: 10.1063/5.0038086] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
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, we evidence a transition from "normal" strong coupling in which the photon modes are coupled to one another via the excitonic transition of the molecular dye to a state in which photon-modes become decoupled. We use an eight-level modified Hamiltonian to describe the optical properties of the system and compare the distribution of the confined optical field in coupled and decoupled structures.
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Affiliation(s)
- Kyriacos Georgiou
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - Kirsty E McGhee
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - Rahul Jayaprakash
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - David G Lidzey
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
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Gu B, Mukamel S. Optical-Cavity Manipulation of Conical Intersections and Singlet Fission in Pentacene Dimers. J Phys Chem Lett 2021; 12:2052-2056. [PMID: 33615792 DOI: 10.1021/acs.jpclett.0c03829] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We demonstrate how the singlet fission process in pentacene dimers mediated by a conical intersection is controlled by coupling the molecule to a confined optical cavity photon mode. By following the polariton quantum dynamics of a conical intersection coupled to a cavity mode taking into account vibrational relaxation and cavity loss, we find that the singlet fission can be significantly suppressed because the polaritonic conical intersection is pushed away from the initial Franck-Condon excitation region.
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Affiliation(s)
- Bing Gu
- Department of Chemistry and Department of Physics & Astronomy, University of California, Irvine, CA 92697, United States
| | - Shaul Mukamel
- Department of Chemistry and Department of Physics & Astronomy, University of California, Irvine, CA 92697, United States
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