Recently Frenkel exciton polaritons (EPs) in organic materials and biological structures attracted considerable interest in relation to their Bose-Einstein condensation, low threshold polariton lasing, and polariton chemistry in microcavity. The concept of EPs suggests strong light-matter interaction that is supported by a considerably larger oscillator strength of organic systems compared to inorganic semiconductors. Polariton absorption of electron-vibrational systems was considered in nanofibers of organic dyes using a realistic non-Markovian model of molecular vibrations [1], and in a single-mode cavity in the presence of Brownian dissipation [2]. Theoretical description of EP luminescence in molecular systems is a challenge since in this case both the interaction with radiation field and electron-vibrational interaction are strong. Elastic cavity emission of polaritons in a single-mode microcavity in the presence of Brownian dissipation from molecular vibrations was considered in Ref.[2] for a specific case when polariton linewidth is the mean of cavity and molecular linewidth, although only at resonance when the cavity frequency is equal to that of a molecular resonance. Meanwhile, the interaction of the polariton with molecular vibrations should depend on exciton contribution to EP. In this work using a realistic non-Markovian theory for the description of the polariton-molecular vibrations interaction we calculate polariton luminescence in the polariton basis. We show that the frequency shift and broadening of polariton luminescence spectra strongly depend on the exciton contribution to the exciton polariton that is a function of frequency. Our non-Markovian theory predicts Fano resonances in EP luminescence and narrowing of its spectrum with an increase in the number of molecules in a single-mode microcavity. We also consider non-equilibrium (hot) EP luminescence that opens a way for its observation in organic-based nanodevices.
[1] B.D. Fainberg, J. Phys. Chem. C 123, 7366 (2019).
[2] K.S.U. Kansanen, J.J. Toppari, and T.T. Heikkila, J. Chem. Phys. 154, 044108 (2021).
Chemically synthesized biomolecules can self-assemble to bioinspired nanostructures of different morphologies such as dots, tubes, spheres, nanofibers and more. They adopt similar basic ordering as their biological counterparts either α-helical or β-sheet peptide/protein conformations. These two fundamental biomolecular architectures exhibit dissimilar physical properties. One of the most interesting physical properties found in biological and bioinspired structures is a new biophotonic phenomenon of visible fluorescence (FL). It has been observed both in neurodegenerative disease-related amyloid fibrils and in synthetic amyloidogenic biorganic di- and tri-aromatic and aliphatic peptide nanostructures. The FL effect has been also found recently in peptide nanodots and hybrid polymer/peptide thin films. All of them have been assembled to β-sheet secondary structure. In this work we report on a new development of FL optical waveguiding in elongated bioinspired fibrillary structures, self-assembled from ultrashort amylodogenic peptides/proteins and hybrid polymer/peptides biomolecules. We show that FL propagation in these two fiber materials of different origin can be described by two completely different mechanisms. One of them is conventional FL propagation in the region of optical transparency of peptide materials in accordance with optical confinement rules. Another model is FL reabsorption mechanism where anomalous long range FL propagation has been found. We show that this intrinsic FL biophotonic waveguiding effects found in different β- sheet biomaterials is considered as a promising tool for precise biomedicine where new biocompatible visible tunable FL optical waveguides can be applied in advanced nanomedical technologies (local bioimaging, light diagnostics, therapy, optogenetitcs and health monitoring).
Purely organic materials with negative and near-zero dielectric permittivity can be easily fabricated, and propa- gation of surface polaritons at the material/air interface was demonstrated. Here we develop a mean- eld theory of nonlinear light-induced "plasmonic" properties of organic materials. The theory describes both a red shift of the resonance frequency of isolated molecules, according to the Clausius-Mossotti Lorentz-Lorentz mecha- nism, and the wide variations of their spectra related to the aggregation of molecules into J- or H-aggregates. The bistable response of organic materials in the condensed phase has been demonstrated using the electron- vibrational model. We predict the generation of the switching waves, or kinks in the bistable organic thin lms that enable us to observe a bistable behaviour of the surface polaritons at the organic thin lm/dielectric inter- face under the laser irradiation. We present the alternating-sign dependence of the switching wave velocity on pump intensity and discuss a possibility of controlling the polariton propagation by switching waves.
Purely organic materials with near-zero dielectric permittivity can be easily fabricated. Here we develop a theory of non-steady-state organic plasmonics with strong short laser pulses that enable us to obtain near-zero dielectric permittivity during a short time. We have proposed to use non-steady-state organic plasmonics for the enhancement of intersite dipolar energy-transfer interaction in the quantum dot wire that in°uences on electron transport through nanojunctions. Such interactions can compensate Coulomb repulsions for particular conditions. We propose the exciton control of Coulomb blocking in the quantum dot wire based on the non- steady-state near-zero dielectric permittivity of the organic host medium.
Graphene electrodes provide a suitable alternative to metal contacts in molecular conduction nanojunctions. Here, we propose to use graphene electrodes as a platform for effective photon assisted tunneling through molecular conduction nanojunctions. We predict dramatic increasing currents evaluated at side-band energies ~ nħω (n is a whole number) related to the modification of graphene gapless spectrum under the action of external electromagnetic field of frequency ω. A side benifit of using doped graphene electrodes is the polarization control of photocurrent related to the processes occurring either in the graphene electrodes or in the molecular bridge. The latter processes are accompanied by surface plasmon excitation in the graphene sheet that makes them more efficient. Our results illustrate the potential of graphene contacts in coherent control of photocurrent in molecular electronics, supporting the possibility of single-molecule devices.
We present a pseudoparticle nonequilibrium Green function formalism as a tool to study the coupling between plasmons and excitons in nonequilibrium molecular junctions. The formalism treats plasmon-exciton couplings and intra-molecular interactions exactly, and is shown to be especially convenient for exploration of plasmonic absorption spectrum of plexitonic systems, where combined electron and energy transfers play an important role. We demonstrate the sensitivity of the molecule-plasmon Fano resonance to junction bias and intra-molecular interactions (Coulomb repulsion and intra-molecular exciton coupling). The electromagnetic theory is used in order to derive self-consistent ¯eld-induced coupling terms between the molecular and the plasmon excitations. Our study opens a way to deal with strongly interacting plasmon-exciton systems in nonequilibrium molecular devices.
Theory of energy transfer interactions between a pair of two level molecules in the molecular
nanojunction including surface plasmon (SP) dressed interaction of plasmonic nanostructure,
replicating metallic leads is presented. Results on the modification of bare dipolar interaction,
known to be responsible for molecular energy transfer processes, in the proximity of metallic
nanosystem are presented. Specifically, the manuscript includes theoretical investigation of
nanosphere (NSP) monomer, nanoshell (NSH) monomer, and coupled nanosphere pair (dimer)
based nanosystems. Closed form analytical expressions for NSP and NSH structures tailored for molecular nanojunction geometry are derived in the theoretical framework of multipole spectral expansion (MSE) method, which is straightforwardly extendible to dimers and multimers. The role of size and dielectric environment on energy transfer is investigated and interpreted. Theory predicts
that the monomer and dimer both enhance the dipolar interaction, yet, dimer geometry is favorable due to its spectral tuning potential originated from plasmon hybridization and true resemblance with typical molecular nanojunctions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.