| 1. |
- Andrén, Daniel, 1991, et al.
(författare)
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Microscopic metavehicles powered and steered by embedded optical metasurfaces
- 2021
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 16:9, s. 970-974
-
Tidskriftsartikel (refereegranskat)abstract
- Nanostructured dielectric metasurfaces offer unprecedented opportunities to manipulate light by imprinting an arbitrary phase gradient on an impinging wavefront(1). This has resulted in the realization of a range of flat analogues to classical optical components, such as lenses, waveplates and axicons(2-6). However, the change in linear and angular optical momentum(7) associated with phase manipulation also results in previously unexploited forces and torques that act on the metasurface itself. Here we show that these optomechanical effects can be utilized to construct optical metavehicles-microscopic particles that can travel long distances under low-intensity plane-wave illumination while being steered by the polarization of the incident light. We demonstrate movement in complex patterns, self-correcting motion and an application as transport vehicles for microscopic cargoes, which include unicellular organisms. The abundance of possible optical metasurfaces attests to the prospect of developing a wide variety of metavehicles with specialized functional behaviours.
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| 2. |
- Baranov, Denis, 1990, et al.
(författare)
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All-dielectric nanophotonics: the quest for better materials and fabrication techniques
- 2017
-
Ingår i: Optica. - : The Optical Society. - 2334-2536. ; 4:7, s. 814-825
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Forskningsöversikt (refereegranskat)abstract
- All-dielectric nanophotonics is an exciting and rapidly developing area of nano-optics that utilizes the resonant behavior of high-index low-loss dielectric nanoparticles to enhance light-matter interaction at the nanoscale. When experimental implementation of a specific all-dielectric nanostructure is desired, two crucial factors have to be considered: the choice of a high-index material and a fabrication method. The degree to which various effects can be enhanced relies on the dielectric response of the chosen material as well as the fabrication accuracy. Here, we provide an overview of available high-index materials and existing fabrication techniques for the realization of all-dielectric nanostructures. We compare performance of the chosen materials in the visible and IR spectral ranges in terms of scattering efficiencies and Q factors of the magnetic Mie resonance. Methods for all-dielectric nanostructure fabrication are discussed and their advantages and disadvantages are highlighted. We also present an outlook for the search for better materials with higher refractive indices and novel fabrication methods that will enable low-cost manufacturing of optically resonant high-index nanoparticles. We believe that this information will be valuable across the field of nanophotonics and particularly for the design of resonant all-dielectric nanostructures.
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| 3. |
- Baranov, Denis, 1990, et al.
(författare)
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Anapole-Enhanced Intrinsic Raman Scattering from Silicon Nanodisks
- 2018
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:7, s. 2730-2736
-
Tidskriftsartikel (refereegranskat)abstract
- Enhancement of inelastic light emission processes through resonant excitation usually correlates with enhanced scattering of the excitation light, as is for example typically the case for surface-enhanced fluorescence and Raman scattering from plasmonic nanostructures. Here, we demonstrate an unusual case where a reverse correlation is instead observed, that is, we measure a multifold enhancement of Raman emission along with suppressed elastic scattering. The system enabling this peculiar effect is composed of silicon nanodisks excited in the so-called anapole state, for which electric and toroidal dipoles interfere destructively in the far-field, thereby preventing elastic scattering, while the optical fields in the core of the silicon particles are enhanced, thus, amplifying light-matter interaction and Raman scattering at the Stokes-shifted emission wavelength. Our results demonstrate an unusual relation between resonances in elastic and inelastic scattering from nanostructures and suggest a route toward background-free frequency conversion devices.
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| 4. |
- Baranov, Denis, 1990, et al.
(författare)
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Circular dichroism mode splitting and bounds to its enhancement with cavity-plasmon-polaritons
- 2020
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Ingår i: Nanophotonics. - : Walter de Gruyter GmbH. - 2192-8614. ; 9:2, s. 283-293
-
Tidskriftsartikel (refereegranskat)abstract
- Geometrical chirality is a widespread phenomenon that has fundamental implications for discriminating enantiomers of biomolecules. In order to enhance the chiral response of the medium, it has been suggested to couple chiral molecules to resonant optical cavities in order to enhance the circular dichroism (CD) signal at the resonant frequency of the cavity. Here, we studied a distinctly different regime of chiral light-matter interaction, wherein the CD signal of a chiral medium splits into polaritonic modes by reaching the strong coupling regime with an optical microcavity. Specifically, we show that by strongly coupling chiral plasmonic nanoparticles to a non-chiral Fabry-Pérot microcavity one can imprint the mode splitting on the CD spectrum of the coupled system and thereby effectively shift the initial chiral resonance to a different energy. We first examined the effect with the use of analytical transfer-matrix method as well as numerical finite-difference time-domain (FDTD) simulations. Furthermore, we confirmed the validity of theoretical predictions in a proof-of-principle experiment involving chiral plasmonic nanoparticles coupled to a Fabry-Pérot microcavity.
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| 5. |
- Baranov, Denis, 1990, et al.
(författare)
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Coherent perfect absorbers: Linear control of light with light
- 2017
-
Ingår i: Nature Reviews Materials. - : Springer Science and Business Media LLC. - 2058-8437. ; 2
-
Forskningsöversikt (refereegranskat)abstract
- The absorption of electromagnetic energy by a material is a phenomenon that underlies many applications, including molecular sensing, photocurrent generation and photodetection. Typically, the incident energy is delivered to the system through a single channel, for example, by a plane wave incident on one side of an absorber. However, absorption can be made much more efficient by exploiting wave interference. A coherent perfect absorber is a system in which the complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves. Here, we review recent advances in the design and applications of such devices. We present the theoretical principles underlying the phenomenon of coherent perfect absorption and give an overview of the photonic structures in which it can be realized, including planar and guided-mode structures, graphene-based systems, parity-symmetric and time-symmetric structures, 3D structures and quantum-mechanical systems. We then discuss possible applications of coherent perfect absorption in nanophotonics, and, finally, we survey the perspectives for the future of this field.
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| 6. |
- Baranov, Denis, 1990, et al.
(författare)
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Coherent virtual absorption based on complex zero excitation for ideal light capturing
- 2017
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Ingår i: Optica. - : The Optical Society. - 2334-2536. ; 4:12, s. 1457-1461
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Tidskriftsartikel (refereegranskat)abstract
- Absorption of light is directly associated with dissipative processes in a material. In suitably tailored resonators, a specific level of dissipation can support coherent perfect absorption, the time-reversed analogue of lasing, which enables total absorption and zero scattering in open cavities. On the contrary, the scattering zeros of lossless objects strictly occur at complex frequencies. While usually considered nonphysical due to their divergent response in time, these zeros play a crucial role in the overall scattering dispersion. Here, we introduce the concept of coherent virtual absorption, accessing these modes by temporally shaping the incident waveform. We show that engaging these complex zeros enables storing and releasing the electromagnetic energy at will within a lossless structure for arbitrary amounts of time, under the control of the impinging field. The effect is robust with respect to inevitable material dissipation and can be realized in systems with any number of input ports. The observed effect may have important implications for flexible control of light propagation and storage, low-energy memory, and optical modulation. (c) 2017 Optical Society of America
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| 7. |
- Baranov, Denis, 1990, et al.
(författare)
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Modifying magnetic dipole spontaneous emission with nanophotonic structures
- 2017
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Ingår i: Laser and Photonics Reviews. - : Wiley. - 1863-8899 .- 1863-8880. ; 11:3, s. Article Number: 1600268-
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Forskningsöversikt (refereegranskat)abstract
- Tailoring of electromagnetic spontaneous emission predicted by E. M. Purcell more than 50 years ago has undoubtedly proven to be one of the most important effects in the rich areas of quantum optics and nanophotonics. Although during the past decades the research in this field has been focused on electric dipole emission, the recent progress in nanofabrication and study of magnetic quantum emitters, such as rare-earth ions, has stimulated the investigation of the magnetic side of spontaneous emission. Here, we review the state-of-the-art advances in the field of spontaneous emission enhancement of magnetic dipole quantum emitters with the use of various nanophotonics systems. We provide the general theory describing the Purcell effect of magnetic emitters, overview realizations of specific nanophotonics structures allowing for the enhanced magnetic dipole spontaneous emission, and give an outlook on the challenges in this field, which remain open to future research.
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| 8. |
- Baranov, Denis, 1990, et al.
(författare)
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Nanophotonic engineering of far-field thermal emitters
- 2019
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 18:9, s. 920-930
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Forskningsöversikt (refereegranskat)abstract
- Thermal emission is a ubiquitous and fundamental process by which all objects at non-zero temperatures radiate electromagnetic energy. This process is often assumed to be incoherent in both space and time, resulting in broadband, omnidirectional light emission toward the far field, with a spectral density related to the emitter temperature by Planck’s law. Over the past two decades, there has been considerable progress in engineering the spectrum, directionality, polarization and temporal response of thermally emitted light using nanostructured materials. This Review summarizes the basic physics of thermal emission, lays out various nanophotonic approaches to engineer thermal emission in the far field, and highlights several applications, including energy harvesting, lighting and radiative cooling.
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| 9. |
- Baranov, Denis, 1990, et al.
(författare)
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Novel Nanostructures and Materials for Strong Light-Matter Interactions
- 2018
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:1, s. 24-42
-
Forskningsöversikt (refereegranskat)abstract
- Quantum mechanical interactions between electromagnetic radiation and matter underlie a broad spectrum of optical phenomena. Strong light-matter interactions result in the well-known vacuum Rabi splitting and emergence of new polaritonic eigenmodes of the coupled system. Thanks to recent progress in nanofabrication, observation of strong coupling has become possible in a great variety of optical nanostructures. Here, we review recently studied and emerging materials for realization of strong light-matter interactions. We present general theoretical formalism describing strong coupling and give an overview of various photonic structures and materials allowing for realization of this regime, including plasmonic and dielectric nanoantennas, novel two-dimensional materials, carbon nanotubes, and molecular vibrational transitions. In addition, we discuss practical applications that can benefit from these effects and give an outlook on unsettled questions that remain open for future research.
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| 10. |
|
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| 11. |
- Baranov, Denis, 1990, et al.
(författare)
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Ultrastrong coupling between nanoparticle plasmons and cavity photons at ambient conditions
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrastrong coupling is a distinct regime of electromagnetic interaction that enables a rich variety of intriguing physical phenomena. Traditionally, this regime has been reached by coupling intersubband transitions of multiple quantum wells, superconducting artificial atoms, or two-dimensional electron gases to microcavity resonators. However, employing these platforms requires demanding experimental conditions such as cryogenic temperatures, strong magnetic fields, and high vacuum. Here, we use a plasmonic nanorod array positioned at the antinode of a resonant optical Fabry-Pérot microcavity to reach the ultrastrong coupling (USC) regime at ambient conditions and without the use of magnetic fields. From optical measurements we extract the value of the interaction strength over the transition energy as high as g/ω ~ 0.55, deep in the USC regime, while the nanorod array occupies only ∼4% of the cavity volume. Moreover, by comparing the resonant energies of the coupled and uncoupled systems, we indirectly observe up to ∼10% modification of the ground-state energy, which is a hallmark of USC. Our results suggest that plasmon-microcavity polaritons are a promising platform for room-temperature USC realizations in the optical and infrared ranges, and may lead to the long-sought direct visualization of the vacuum energy modification.
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| 12. |
- Canales Ramos, Adriana, 1993, et al.
(författare)
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Abundance of cavity-free polaritonic states in resonant materials and nanostructures
- 2021
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 154:2
-
Tidskriftsartikel (refereegranskat)abstract
- Strong coupling between various kinds of material excitations and optical modes has recently shown potential to modify chemical reaction rates in both excited and ground states. The ground-state modification in chemical reaction rates has usually been reported by coupling a vibrational mode of an organic molecule to the vacuum field of an external optical cavity, such as a planar Fabry-Pérot microcavity made of two metallic mirrors. However, using an external cavity to form polaritonic states might (i) limit the scope of possible applications of such systems and (ii) might be unnecessary. Here, we highlight the possibility of using optical modes sustained by materials themselves to self-couple to their own electronic or vibrational resonances. By tracing the roots of the corresponding dispersion relations in the complex frequency plane, we show that electronic and vibrational polaritons are natural eigenstates of bulk and nanostructured resonant materials that require no external cavity. Several concrete examples such as a slab of the excitonic material and a spherical water droplet in vacuum are shown to reach the regime of such cavity-free self-strong coupling. The abundance of cavity-free polaritons in simple and natural structures points at their relevance and potential practical importance for the emerging field of polaritonic chemistry, exciton transport, and modified material properties.
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| 13. |
- Canales Ramos, Adriana, 1993, et al.
(författare)
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Polaritonic linewidth asymmetry in the strong and ultrastrong coupling regime
- 2023
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Ingår i: Nanophotonics. - 2192-8614. ; 12:21, s. 4073-4086
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Tidskriftsartikel (refereegranskat)abstract
- The intriguing properties of polaritons resulting from strong and ultrastrong light–matter coupling have been extensively investigated. However, most research has focused on spectroscopic characteristics of polaritons, such as their eigenfrequencies and Rabi splitting. Here, we study the decay rates of a plasmon–microcavity system in the strong and ultrastrong coupling regimes experimentally and numerically. We use a classical scattering matrix approach, approximating our plasmonic system with an effective Lorentz model, to obtain the decay rates through the imaginary part of the complex quasinormal mode eigenfrequencies. Our classical model automatically includes all the interaction terms necessary to account for ultrastrong coupling without dealing with the rotating-wave approximation and the diamagnetic term. We find an asymmetry in polaritonic decay rates, which deviate from the expected average of the uncoupled system’s decay rates at zero detuning. Although this phenomenon has been previously observed in exciton–polaritons and attributed to their disorder, we observe it even in our homogeneous system. As the coupling strength of the plasmon–microcavity system increases, the asymmetry also increases and can become so significant that the lower (upper) polariton decay rate reduction (increase) goes beyond the uncoupled decay rates, γ − < γ 0,c < γ +. Furthermore, our findings demonstrate that polaritonic linewidth asymmetry is a generic phenomenon that persists even in the case of bulk polaritons.
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| 14. |
- Cuadra, Jorge, 1982, et al.
(författare)
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Observation of Tunable Charged Exciton Polaritons in Hybrid Monolayer WS 2 -Plasmonic Nanoantenna System
- 2018
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 18:3, s. 1777-1785
-
Tidskriftsartikel (refereegranskat)abstract
- © 2018 American Chemical Society. Formation of dressed light-matter states in optical structures, manifested as Rabi splitting of the eigen energies of a coupled system, is one of the key effects in quantum optics. In pursuing this regime with semiconductors, light is usually made to interact with excitons, electrically neutral quasiparticles of semiconductors; meanwhile interactions with charged three-particle states, trions, have received little attention. Here, we report on strong interaction between localized surface plasmons in silver nanoprisms and excitons and trions in monolayer tungsten disulfide (WS 2 ). We show that the plasmon-exciton interactions in this system can be efficiently tuned by controlling the charged versus neutral exciton contribution to the coupling process. In particular, we show that a stable trion state emerges and couples efficiently to the plasmon resonance at low temperature by forming three bright intermixed plasmon-exciton-trion polariton states. Our findings open up a possibility to exploit electrically charged polaritons at the single nanoparticle level.
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| 15. |
- Ermolaev, Georgy A., et al.
(författare)
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Broadband optical properties of monolayer and bulk MoS 2
- 2020
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Ingår i: npj 2D Materials and Applications. - : Springer Science and Business Media LLC. - 2397-7132. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Layered semiconductors such as transition metal dichalcogenides (TMDs) offer endless possibilities for designing modern photonic and optoelectronic components. However, their optical engineering is still a challenging task owing to multiple obstacles, including the absence of a rapid, contactless, and the reliable method to obtain their dielectric function as well as to evaluate in situ the changes in optical constants and exciton binding energies. Here, we present an advanced approach based on ellipsometry measurements for retrieval of dielectric functions and the excitonic properties of both monolayer and bulk TMDs. Using this method, we conduct a detailed study of monolayer MoS2 and its bulk crystal in the broad spectral range (290–3300 nm). In the near- and mid-infrared ranges, both configurations appear to have no optical absorption and possess an extremely high dielectric permittivity making them favorable for lossless subwavelength photonics. In addition, the proposed approach opens a possibility to observe a previously unreported peak in the dielectric function of monolayer MoS2 induced by the use of perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS) seeding promoters for MoS2 synthesis and thus enables its applications in chemical and biological sensing. Therefore, this technique as a whole offers a state-of-the-art metrological tool for next-generation TMD-based devices.
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| 16. |
- Ermolaev, G. A., et al.
(författare)
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Giant optical anisotropy in transition metal dichalcogenides for next-generation photonics
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Large optical anisotropy observed in a broad spectral range is of paramount importance for efficient light manipulation in countless devices. Although a giant anisotropy has been recently observed in the mid-infrared wavelength range, for visible and near-infrared spectral intervals, the problem remains acute with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN crystals. This issue inspired an intensive search for giant optical anisotropy among natural and artificial materials. Here, we demonstrate that layered transition metal dichalcogenides (TMDCs) provide an answer to this quest owing to their fundamental differences between intralayer strong covalent bonding and weak interlayer van der Waals interaction. To do this, we made correlative far- and near-field characterizations validated by first-principle calculations that reveal a huge birefringence of 1.5 in the infrared and 3 in the visible light for MoS2. Our findings demonstrate that this remarkable anisotropy allows for tackling the diffraction limit enabling an avenue for on-chip next-generation photonics. Optical anisotropy in a broad spectral range is pivotal to efficient light manipulation. Here, the authors measure a birefringence of 1.5 in the infrared range and 3 in the visible light for MoS2.
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| 17. |
- Green, Thomas D, 1984, et al.
(författare)
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Optical material anisotropy in high-index transition metal dichalcogenide Mie nanoresonators
- 2020
-
Ingår i: Optica. - 2334-2536. ; 7:6, s. 680-686
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Tidskriftsartikel (refereegranskat)abstract
- Resonant optical antennas provide unprecedented opportunities to control light on length scales far below the diffraction limit. Recent studies have demonstrated that nanostructures made of multilayer transition metal dichalcogenides (TMDCs) can exhibit well-defined and intense Mie resonances in the visible to the near-infrared spectral range. These resonances are realizable because the TMDC materials exhibit very high in-plane refractive indices, in fact higher than what is found in typical high-index dielectric materials like Si orGaAs. However, their out-of-plane refractive indices are comparatively low. Here we experimentally and theoretically investigate how this unusually large material anisotropy influences the optical response of individual TMDC nanoresonators made of MoS2. We find that anisotropy strongly affects the far-field optical response of the resonators, as well as complex interference effects, such as anapole and resonant Kerker conditions. Moreover, we show that it is possible to utilize the material anisotropy to probe the vectorial nature of the nanoresonator internal near fields. Specifically, we show that Raman spectra originating from individual MoS2 nanoresonators exhibit mode-specific anisotropic enhancement factors that vary with the nanoresonator size and correlate with specific modes supported at resonance. Our study indicates that exploring material anisotropy in novel high-index dielectrics may lead to new nanophotonic effects and applications. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 18. |
- Hertzog, Manuel, 1989, et al.
(författare)
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Enhancing Vibrational Light-Matter Coupling Strength beyond the Molecular Concentration Limit Using Plasmonic Arrays
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:3, s. 1320-1326
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Tidskriftsartikel (refereegranskat)abstract
- Vibrational strong coupling is emerging as a promising tool to modify molecular properties by making use of hybrid light-matter states known as polaritons. Fabry-Perot cavities filled with organic molecules are typically used, and the molecular concentration limits the maximum reachable coupling strength. Developing methods to increase the coupling strength beyond the molecular concentration limit are highly desirable. In this Letter, we investigate the effect of adding a gold nanorod array into a cavity containing pure organic molecules using FT-IR microscopy and numerical modeling. Incorporation of the plasmonic nanorod array that acts as artificial molecules leads to an order of magnitude increase in the total coupling strength for the cavity with matching resonant frequency filled with organic molecules. Additionally, we observe a significant narrowing of the plasmon line width inside the cavity. We anticipate that these results will be a step forward in exploring vibropolaritonic chemistry and may be used in plasmon based biosensors.
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| 19. |
- Krasnok, Alex, et al.
(författare)
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Anomalies in light scattering
- 2019
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Ingår i: Advances in Optics and Photonics. - 1943-8206. ; 11:4, s. 892-951
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Forskningsöversikt (refereegranskat)abstract
- The scattering of electromagnetic waves lies at the heart of most experimental techniques over nearly the entire electromagnetic spectrum, ranging from radio waves to optics and x rays. Hence, deep insight into the basics of scattering theory and an understanding of the peculiar features of electromagnetic scattering are necessary for the correct interpretation of experimental data and an understanding of the underlying physics. Recently, a broad spectrum of exceptional scattering phenomena attainable in suitably engineered structures has been predicted and demonstrated. Examples include bound states in the continuum, exceptional points in parity-time (PT)-symmetrical non-Hermitian systems, coherent perfect absorption, virtual perfect absorption, nontrivial lasing, nonradiating sources, and others. In this paper, we establish a unified description of such exotic scattering phenomena and show that the origin of ail these effects can be traced back to the properties of poles and zeros of the underlying scattering matrix. We provide insights on how managing these special points in the complex frequency plane provides a powerful approach to tailor unusual scattering regimes. (C) 2019 Optical Society of America
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| 20. |
- Krasnok, A. E., et al.
(författare)
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All-Dielectric Nanophotonics: Fundamentals, Fabrication, and Applications
- 2018
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Ingår i: World Scientific Series in Nanoscience and Nanotechnology. - : World Scientific. - 2301-301X .- 2335-6693. ; 16, s. 337-385
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter reviews a novel, rapidly developing field of modern light science named all-dielectric nanophotonics. This branch of nanophotonics is based on the properties of high-index dielectric nanoparticles which allow for controlling both magnetic and electric responses of a nanostructured matter. Here, we discuss optical properties of high-index dielectric nanoparticles, methods of their fabrication, and recent advances in practical applications, including the quantum source emission engineering, Fano resonances in all-dielectric nanoclusters, surface enhanced spectroscopy and sensing, coupled-resonator optical waveguides, metamaterials and metasurfaces, and nonlinear nanophotonics.
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| 21. |
- Krasnok, A. E., et al.
(författare)
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All-Optical Switching and Unidirectional Plasmon Launching with Nonlinear Dielectric Nanoantennas
- 2018
-
Ingår i: Physical Review Applied. - 2331-7019. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- High-index dielectric nanoparticles have become a powerful platform for nonlinear nanophotonics due to special types of optical nonlinearity, e.g. caused by electron-hole plasma (EHP) photoexcitation. We propose a highly tunable dielectric nanoantenna consisting of a chain of silicon particles excited by a dipole emitter. The nanoantenna exhibits slow group-velocity guided modes, corresponding to the Van Hove singularity in an infinite structure, which enable a large Purcell factor up to several hundred and are very sensitive to the nanoparticle permittivity. This sensitivity enables the nanoantenna tuning via EHP excitation with an ultrafast laser pumping. Dramatic variations in the nanoantenna radiation patterns and Purcell factor caused by ultrafast laser pumping of several boundary nanoparticles with relatively low intensities of about 25 GW/cm2 are shown. Unidirectional surface-plasmon polaritons launching with EHP excitation in the nanoantenna on a Ag substrate is demonstrated.
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| 22. |
- Krasnok, A. E., et al.
(författare)
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Coherently Enhanced Wireless Power Transfer
- 2018
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 120:14
-
Tidskriftsartikel (refereegranskat)abstract
- Extraction of electromagnetic energy by an antenna from impinging external radiation is at the basis of wireless communications and wireless power transfer (WPT). The maximum of transferred energy is ensured when the antenna is conjugately matched, i.e., when it is resonant and it has an equal coupling with free space and its load. This condition, however, can be easily affected by changes in the environment, preventing optimal operation of a WPT system. Here, we introduce the concept of coherently enhanced WPT that allows us to bypass this difficulty and achieve dynamic control of power transfer. The approach relies on coherent excitation of the waveguide connected to the antenna load with a backward propagating signal of specific amplitude and phase. This signal creates a suitable interference pattern at the load resulting in a modification of the local wave impedance, which in turn enables conjugate matching and a largely increased amount of extracted energy. We develop a simple theoretical model describing this concept, demonstrate it with full-wave numerical simulations for the canonical example of a dipole antenna, and verify experimentally in both near-field and far-field regimes.
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| 23. |
- Krasnok, A. E., et al.
(författare)
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Virtual electromagnetic absorption and energy storage by a Hermitian system via complex frequency excitation
- 2017
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Ingår i: 2017 Conference on Lasers and Electro-Optics, CLEO 2017 - Proceedings. ; Part F42-CLEO_QELS 2017, s. paper FM1G.3-
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Konferensbidrag (refereegranskat)abstract
- Hermitian systems, with no Ohmic loss, support virtual absorbing modes located in the complex frequency plane. Although being usually considered non-physical due to their divergent exponential time dependence, these modes play a crucial role in the overall scattering response. Here, we access these modes and use them for virtual absorption and storage of light by specifically shaping the incident excitation with exponentially growing envelopes.
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| 24. |
- Li, S., et al.
(författare)
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Coherently enhanced wireless power transfer: Theory and experiment
- 2018
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1092
-
Konferensbidrag (refereegranskat)abstract
- Extraction of electromagnetic energy by an antenna to a coupled waveguide is the crucial part of wireless power transfer. Efficiency of this process is usually defined by the coupling strength between the antenna and the outcoupling waveguide or cable. We show that there is an additional possibility to improve the receiving efficiency by coherent excitation of the outcoupling waveguide by a backward propagating guided mode with a specific amplitude and phase. This additional wave creates a special interference picture in the system and result in increased amount of energy extracted to the waveguide from the free space. We develop a simple analytical model predicting this effect, demonstrate it in numerical FDTD simulations, and verify in microwave experiment.
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| 25. |
- Li, S., et al.
(författare)
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Dielectric chain driven by electron-hole plasma photoexcitation
- 2017
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Ingår i: Proceedings of the International Conference Days on Diffraction 2017, DD 2017. - 9781538647967 ; 2017-December, s. 214-218
-
Konferensbidrag (refereegranskat)abstract
- All-dielectric nanophotonics based on high-index dielectric nanoparticles became a powerful platform for modern light science, providing many fascinating applications, including high-efficient nanoantennas and metamaterials. High-index dielectric nanostructures are of a special interest for nonlinear nanophotonics, where they demonstrate special types of optical nonlinearity, such as electron-hole plasma photoexcitation, which are not inherent to plasmonic nanostructures. Here, we propose a novel type of highly tunable all-dielectric Yagi-Uda nanoantennas, consisting of a chain of Si nanoparticles exciting by an electric dipole source, which allow tuning of their radiating properties via electron-hole plasma photoexcitation. We theoretically and numerically demonstrate the tuning of radiation power patterns and the Purcell factor by additional pumping of several boundary nanoparticles with relatively low peak intensities of fs-laser.
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| 26. |
- Li, S., et al.
(författare)
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Dielectric Yagi-Uda nanoantennas driven by electron-hole plasma photoexcitation
- 2017
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 917:6
-
Konferensbidrag (refereegranskat)abstract
- All-dielectric nanophotonics based on high-index dielectric nanoparticles became a powerful platform for modern light science, providing many fascinating applications, including high-efficient nanoantennas and metamaterials. High-index dielectric nanostructures are of a special interest for nonlinear nanophotonics, where they demonstrate special types of optical nonlinearity, such as electron-hole plasma photoexcitation, which are not inherent to plasmonic nanostructures. Here, we propose a novel type of highly tunable all-dielectric Yagi-Uda nanoantennas, consisting of a chain of Si nanoparticles exciting by an electric dipole source, which allow tuning of their radiating properties via electron-hole plasma photoexcitation. We theoretically and numerically demonstrate the tuning of radiation power patterns and the Purcell effect by additional pumping of several boundary nanoparticles with relatively low peak intensities of fs-laser.
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| 27. |
- Maciel-Escudero, Carlos, et al.
(författare)
-
Probing optical anapoles with fast electron beams
- 2023
-
Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optical anapoles are intriguing charge-current distributions characterized by a strong suppression of electromagnetic radiation. They originate from the destructive interference of the radiation produced by electric and toroidal multipoles. Although anapoles in dielectric structures have been probed and mapped with a combination of near- and far-field optical techniques, their excitation using fast electron beams has not been explored so far. Here, we theoretically and experimentally analyze the excitation of optical anapoles in tungsten disulfide (WS2) nanodisks using Electron Energy Loss Spectroscopy (EELS) in Scanning Transmission Electron Microscopy (STEM). We observe prominent dips in the electron energy loss spectra and associate them with the excitation of optical anapoles and anapole-exciton hybrids. We are able to map the anapoles excited in the WS2 nanodisks with subnanometer resolution and find that their excitation can be controlled by placing the electron beam at different positions on the nanodisk. Considering current research on the anapole phenomenon, we envision EELS in STEM to become a useful tool for accessing optical anapoles appearing in a variety of dielectric nanoresonators.
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| 28. |
- Milichko, V., et al.
(författare)
-
Metal-dielectric nanocavity as a versatile optical sensing platform
- 2017
-
Ingår i: Metamaterials. - 1873-1988. ; , s. 403-405
-
Konferensbidrag (refereegranskat)abstract
- © 2017 IEEE. The control of various processes at nanoscale in a real time and easy manner is a challenge for different applications: from lab-on-A-chip to catalysis and medical diagnostic systems. Here, we demonstrate a new system, representing a metal-dielectric (hybrid) nanocavity for multifunctional sensing at nanoscale. The cavity provides enhancement of Raman signal and simultaneous control of the analyte temperature. We believe, the proposed concept provides a universal optical tool not only for the basic life sciences, but also for nanotechnology and nanomedicine.
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| 29. |
- Milichko, V., et al.
(författare)
-
Metal-Dielectric Nanocavity for Real-Time Tracing Molecular Events with Temperature Feedback
- 2018
-
Ingår i: Laser and Photonics Reviews. - : Wiley. - 1863-8899 .- 1863-8880. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Plasmonic nanoparticles coupled with metallic films forming nanometer scale cavities have recently emerged as a powerful tool for enhancement of light-matter interaction. Despite high efficiency for sensing and light emission, such nanocavities exhibit harmful and uncontrolled optical heating which limits the ranges of light intensities and working temperature. In contrast to plasmonic nanoparticles, all-dielectric counterparts possess low Ohmic losses, high temperature stability along with a strong temperature-dependent Raman response. Here, we demonstrate that a silicon nanoparticle coupled with a thin gold film can serve as a multifunctional metal-dielectric (hybrid) nanocavity operating up to 1200 K. Resonant interaction of light with such nanocavity enables molecular sensing, heat-induced molecular events (protein unfolding), and their real-time tracing with a nanoscale thermometry through the monitoring enhanced Raman scattering both from the nanoparticle and analyzed molecules. We model numerically the thermo-optical properties of the hybrid nanocavity and reveal two alternative regimes of operation - with and without strong optical heating while other functionalities are preserved. We believe that the concept of the multifunctional hybrid nanocavities holds great potential for diverse photochemical and photophysical applications.
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| 30. |
- Munkhbat, Battulga, 1988, et al.
(författare)
-
Electrical Control of Hybrid Monolayer Tungsten Disulfide-Plasmonic Nanoantenna Light-Matter States at Cryogenic and Room Temperatures
- 2020
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 14:1, s. 1196-1206
-
Tidskriftsartikel (refereegranskat)abstract
- Hybrid light-matter states-polaritons-have attracted considerable scientific interest recently, motivated by their potential for development of nonlinear and quantum optical schemes. To realize such states, monolayer transition metal dichalcogenides (TMDCs) have been widely employed as excitonic materials. In addition to neutral excitons, TMDCs host charged excitons, which enables active tuning of hybrid light-matter states by electrical means. Although several reports demonstrated charged exciton-polaritons in various systems, the full-range interaction control attainable at room temperature has not been realized. Here, we demonstrate electrically tunable charged exciton-plasmon polaritons in a hybrid tungsten disulfide (WS2) monolayer-plasmonic nanoantenna system. We show that electrical gating of monolayer WS2 allows tuning the oscillator strengths of neutral and charged excitons not only at cryogenic but also at room temperature, both at vacuum and atmospheric pressure. Such electrical control enables a full-range tunable switching from strong neutral exciton-plasmon coupling to strong charged exciton-plasmon coupling. Our experimental findings allow discussing beneficial and limiting factors of charged exciton-plasmon polaritons, as well as offer routes toward realization of charged polaritonic devices at ambient conditions.
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| 31. |
- Munkhbat, Battulga, 1988, et al.
(författare)
-
Nanostructured Transition Metal Dichalcogenide Multilayers for Advanced Nanophotonics
- 2023
-
Ingår i: Laser and Photonics Reviews. - : Wiley. - 1863-8899 .- 1863-8880. ; 17:1
-
Tidskriftsartikel (refereegranskat)abstract
- Transition metal dichalcogenides (TMDs) attract significant attention due to their exceptional optical, excitonic, mechanical, and electronic properties. Nanostructured multilayer TMDs were recently shown to be highly promising for nanophotonic applications, as motivated by their exceptionally high refractive indices and optical anisotropy. Here, this vision is extended to more sophisticated structures, such as periodic arrays of nanodisks and nanoholes with ultra sharp walls, as well as proof-of-concept all-TMD waveguides and resonators. Specific focus is given to various advanced nanofabrication strategies, including careful selection of resists for electron beam lithography and etching methods, especially for non-conductiven but relevant for nanophotonic applications substrates, such as SiO2. The specific materials studied here include semiconducting WS2, in-plane anisotropic ReS2, and metallic TaSe2, TaS2, and NbSe2. The resulting nanostructures can potentially impact several nanophotonic and optoelectronic areas, including high-index nanophotonics, plasmonics and on-chip optical circuits. The knowledge of TMD material-dependent nanofabrication parameters developed here will help broaden the scope of future applications of all-TMD nanophotonics.
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| 32. |
- Munkhbat, Battulga, 1988, et al.
(författare)
-
Self-Hybridized Exciton-Polaritons in Multilayers of Transition Metal Dichalcogenides for Efficient Light Absorption
- 2019
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 6:1, s. 139-147
-
Tidskriftsartikel (refereegranskat)abstract
- Transition metal dichalcogenides (TMDCs) have attracted significant attention recently in the context of strong light–matter interaction. To observe strong coupling using these materials, excitons are typically hybridized with resonant photonic modes of stand-alone optical cavities, such as Fabry–Pérot microcavities or plasmonic nanoantennas. Here, we show that thick flakes of layered van der Waals TMDCs can themselves serve as low-quality resonators due to their high background permittivity. Optical modes of such “cavities” can in turn hybridize with excitons in the same material. We perform an experimental and theoretical study of such self-hybridization in thick flakes of four common TMDC materials: WS2, WSe2, MoS2, and MoSe2. We observe splitting in reflection and transmission spectra in all four cases and provide angle-resolved dispersion measurements of exciton-polaritons as well as thickness-dependent data. Moreover, we observe significant enhancement and broadening of absorption in thick TMDC multilayers, which can be interpreted in terms of strong light–matter coupling. Remarkably, absorption reaches >50% efficiency across the entire visible spectrum, while simultaneously being weakly dependent on polarization and angle of incidence. Our results thus suggest formation of self-hybridized exciton-polaritons in thick TMDC flakes, which in turn may pave the way toward polaritonic and optoelectronic devices in these simple systems.
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| 33. |
- Munkhbat, Battulga, 1988, et al.
(författare)
-
Suppression of photo-oxidation of organic chromophores by strong coupling to plasmonic nanoantennas
- 2018
-
Ingår i: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 4:7
-
Tidskriftsartikel (refereegranskat)abstract
- Intermixed light-matter quasi-particles—polaritons—have unique optical properties owing to their compositional nature. These intriguing hybrid states have been extensively studied over the past decades in a wide range of realizations aiming at both basic science and emerging applications. However, recently, it has been demonstrated that not only optical but also material-related properties, such as chemical reactivity and charge transport, may be significantly altered in the strong coupling regime of light-matter interactions. We show that a nanoscale system, composed of a plasmonic nanoprism strongly coupled to excitons in a J-aggregated form of organic chromophores, experiences modified excited-state dynamics and, therefore, modified photochemical reactivity. Our experimental results reveal that photobleaching, one of the most fundamental photochemical reactions, can be effectively controlled and suppressed by the degree of plasmon-exciton coupling and detuning. In particular, we observe a 100-fold stabilization of organic dyes for the red-detuned nanoparticles. Our findings contribute to understanding of photochemical properties in the strong coupling regime and may find important implications for the performance and improved stability of optical devices incorporating organic dyes.
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| 34. |
- Munkhbat, Battulga, 1988, et al.
(författare)
-
Transition metal dichalcogenide metamaterials with atomic precision
- 2020
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to extract materials just a few atoms thick has led to the discoveries of graphene, monolayer transition metal dichalcogenides (TMDs), and other important two-dimensional materials. The next step in promoting the understanding and utility of flatland physics is to study the one-dimensional edges of these two-dimensional materials as well as to control the edge-plane ratio. Edges typically exhibit properties that are unique and distinctly different from those of planes and bulk. Thus, controlling the edges would allow the design of materials with combined edge-plane-bulk characteristics and tailored properties, that is, TMD metamaterials. However, the enabling technology to explore such metamaterials with high precision has not yet been developed. Here we report a facile and controllable anisotropic wet etching method that allows scalable fabrication of TMD metamaterials with atomic precision. We show that TMDs can be etched along certain crystallographic axes, such that the obtained edges are nearly atomically sharp and exclusively zigzag-terminated. This results in hexagonal nanostructures of predefined order and complexity, including few-nanometer-thin nanoribbons and nanojunctions. Thus, this method enables future studies of a broad range of TMD metamaterials through atomically precise control of the structure.
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| 35. |
- Munkhbat, Battulga, 1988, et al.
(författare)
-
Tunable self-assembled Casimir microcavities and polaritons
- 2021
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 597:7875, s. 214-219
-
Tidskriftsartikel (refereegranskat)abstract
- Spontaneous formation of ordered structures—self-assembly—is ubiquitous in nature and observed on different length scales, ranging from atomic and molecular systems to micrometre-scale objects and living matter1. Self-ordering in molecular and biological systems typically involves short-range hydrophobic and van der Waals interactions2,3. Here we introduce an approach to micrometre-scale self-assembly based on the joint action of attractive Casimir and repulsive electrostatic forces arising between charged metallic nanoflakes in an aqueous solution. This system forms a self-assembled optical Fabry–Pérot microcavity with a fundamental mode in the visible range (long-range separation distance about 100–200 nanometres) and a tunable equilibrium configuration. Furthermore, by placing an excitonic material in the microcavity region, we are able to realize hybrid light–matter states (polaritons4–6), whose properties, such as coupling strength and eigenstate composition, can be controlled in real time by the concentration of ligand molecules in the solution and light pressure. These Casimir microcavities could find future use as sensitive and tunable platforms for a variety of applications, including opto-mechanics7, nanomachinery8 and cavity-induced polaritonic chemistry9.
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| 36. |
- Proskurin, Alexey, et al.
(författare)
-
Perfect Absorption of a Focused Light Beam by a Single Nanoparticle
- 2021
-
Ingår i: Laser and Photonics Reviews. - : Wiley. - 1863-8899 .- 1863-8880. ; 15:8
-
Tidskriftsartikel (refereegranskat)abstract
- Absorption of electromagnetic energy by a dissipative material is one of the most fundamental electromagnetic processes that underlies a plethora of applied problems, including sensing, radar detection, wireless power transfer, and photovoltaics. Common wisdom is that a finite dissipative object illuminated by a plane wave removes only a finite amount of the wave's energy flux, which is determined by the object's absorption cross-section. Thus, it is of fundamental interest to see if any far-field waveform can be perfectly absorbed by a finite object. Here, it is theoretically demonstrated that a precisely tailored light beam containing only far-field components can be perfectly absorbed by a finite scatterer on a substrate. The self-consistent scattering problem in the dipole approximation is analytically solved and finds a closed-form expression for the spatial spectrum of the incident field and the required complex polarizability of the particle. All analytical predictions are confirmed with full-wave simulations. The results introduce a qualitatively novel class of perfect absorption phenomena in electromagnetics and other wave processes.
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| 37. |
- Rousseaux, Benjamin, 1988, et al.
(författare)
-
Quantum description and emergence of nonlinearities in strongly coupled single-emitter nanoantenna systems
- 2018
-
Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 98:4
-
Tidskriftsartikel (refereegranskat)abstract
- Realizing strong coupling between a single quantum emitter (QE) and an optical cavity is of crucial importance in the context of various quantum optical applications. Although Rabi splitting of single quantum emitters coupled to high-Q classical cavities has been reported in numerous configurations, attaining single emitter Rabi splitting with a plasmonic nanostructure remains a challenge. In particular, strong coupling at the single QE regime would open the path for the realization of single-photon nonlinearities. In this paper, we derive a plasmon quantization procedure for systems consisting of a single QE located in the gap of a nanoantenna. This procedure leads to the description of the quantum dynamics by a master equation for the state of the QE and the quantized plasmonic modes, which is crucial to demonstrate the emergence of single-photon nonlinearities. We investigate numerically the optical response and the resulting Rabi splitting in metallic nanoantennas and find the optimal geometries for the emergence of the strong-coupling regime with single QEs. Finally, we demonstrate the saturation of hybridized modes for a chosen configuration. Our results will be useful for implementation of realistic quantum plasmonic nanosystems involving single QEs at room temperature.
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| 38. |
- Rousseaux, Benjamin, 1988, et al.
(författare)
-
Strong coupling as an interplay of quantum emitter hybridization with plasmonic dark and bright modes
- 2020
-
Ingår i: Physical Review Research. - 2643-1564. ; 2:3
-
Tidskriftsartikel (refereegranskat)abstract
- Strong coupling between a single quantum emitter and an electromagnetic mode is one of the key effects in quantum optics. In the cavity QED approach to plasmonics, strongly coupled systems are usually understood as single-transition emitters resonantly coupled to a single radiative plasmonic mode. However, plasmonic cavities also support nonradiative (or "dark") modes, which offer much higher coupling strengths. On the other hand, realistic quantum emitters often support multiple electronic transitions of various symmetries, which could overlap with higher order plasmonic transitions-in the blue or ultraviolet part of the spectrum. Here, we show that despite very large detuning between a bright mode and an excitonic transition, their strong coupling can be ensured by leveraging higher energy dark modes of the optical cavity. Specifically, when a dark mode interacts strongly with an excitonic transition, the lower polariton of the hybridized spectrum can be pushed to energies of the bright mode. The resulting interaction of the lower dark-mode-exciton polariton and bright mode yields significant vacuum Rabi splitting, which hinges on the existence of the dark mode. We develop a simple model illustrating the modification of the system response in the "dark" strong coupling regime and demonstrate single photon nonlinearity. These results may find important implications in the emerging field of room-temperature quantum plasmonics.
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| 39. |
- Savelev, R. S., et al.
(författare)
-
Dynamically reconfigurable metal-semiconductor Yagi-Uda nanoantenna
- 2017
-
Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 95:23, s. Article Number: 235409-
-
Tidskriftsartikel (refereegranskat)abstract
- We theoretically investigate the properties of a tunable Yagi-Uda nanoantenna composed of metal-dielectric (Ag-Ge) core-shell nanoparticles. We show that, due to the combination of two types of resonances in each nanoparticle, such hybrid Yagi-Uda nanoantenna can operate in two different regimes. Besides the conventional nonresonant operation regime at low frequencies, characterized by highly directive emission in the forward direction, there is another one at higher frequencies caused by a hybrid magneto-electric response of the core-shell nanoparticles. This regime is based on the excitation of the van Hove singularity, and emission in this regime is accompanied by high values of directivity and Purcell factor within the same narrow frequency range. Our analysis reveals the possibility of flexible dynamical tuning of the hybrid nanoantenna emission pattern via electron-hole plasma excitation by 100 fs pump pulse with relatively low peak intensities similar to 200 MWcm(-2).
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| 40. |
- Savelev, R.S., et al.
(författare)
-
Nonlinear core-shell yagi-uda nanoantenna for highly tunable directive emission
- 2017
-
Ingår i: 2017 Conference on Lasers and Electro-Optics, CLEO 2017 - Proceedings. - 9781943580279 ; Part F43-CLEO_AT 2017
-
Konferensbidrag (refereegranskat)abstract
- We propose a novel type of tunable Yagi-Uda nanoantenna composed of metal-dielectric (Ag- Ge) core-shell nanoparticles. By choosing the appropriate nanoantenna parameters we excite a Van Hove singularity, supporting high values of directivity and Purcell factor within the same narrow frequency range. Our analysis reveals the possibility of flexible dynamical tuning of the hybrid nanoantenna emission pattern via electron-hole plasma excitation by additional fs-laser signal pulses.
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| 41. |
- Savelev, Roman S., et al.
(författare)
-
Ultrafast Tunable Hybrid Yagi-Uda Nanoantenna
- 2017
-
Ingår i: Progress in Electromagnetics Research Symposium. - 1559-9450 .- 1931-7360. ; , s. 3854-3858
-
Konferensbidrag (refereegranskat)abstract
- We study radiation from Yagi-Uda nanoantennas composed of metal-dielectric core-shell nanoparticles. We have found an interesting operation regime in such nanoantennas determined by their hybrid nature. This regime rests on the excitation of the Van Hove singularity, supporting high values of directivity and Purcell factor within the same narrow frequency range. In this regime, a strong dynamical tuning of the emission pattern via electron-hole plasma photoexcitation by a femtosecond pumping can be achieved.
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| 42. |
- Sergaeva, O.N., et al.
(författare)
-
Core-shell Yagi-Uda nanoantenna for highly efficient and directive emission
- 2017
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 929:1
-
Konferensbidrag (refereegranskat)abstract
- We study radiation from hybrid Yagi-Uda nanoantennas composed of metal-dielectric core-shell nanoparticles. We show that due to the presence of two types of resonances in each particle at close frequencies the hybrid Yagi-Uda nanoantenna can operate in two different regimes. In the first regime at low frequencies it operates similarly to plasmonic and all-dielectric Yagi-Uda nanoantennas, and it is characterized with highly directive emission in a forward direction. In the second regime at higher frequencies the hybrid nanoantenna can emit with a high directivity in backward direction due to the presence of the hybrid dispersion branch with negative group velocity. Moreover by choosing the appropriate nanoantenna parameters one can achieve the operation regime when due to excitation of dark magnetic dipole modes in nanoantenna high values of directivity and Purcell factor are realized simultaneouslly in extremely narrow frequency range.
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| 43. |
- Stührenberg, Michael, 1987, et al.
(författare)
-
Strong Light-Matter Coupling between Plasmons in Individual Gold Bi-pyramids and Excitons in Mono- and Multilayer WSe2
- 2018
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 18:9, s. 5938-5945
-
Tidskriftsartikel (refereegranskat)abstract
- Monolayer transition-metal dichalcogenides (TMDCs) have attracted a lot of research attention recently, motivated by their remarkable optical properties and potential for strong light-matter interactions. Realization of strong plasmon-exciton coupling is especially desirable in this context because it holds promise for the enabling of room-temperature quantum and nonlinear optical applications. These efforts naturally require investigations at a single-nanoantenna level, which, in turn, should possess a compact optical mode interacting with a small amount of excitonic material. However, standard plasmonic nanoantenna designs such as nanoparticle dimers or particle-on-film suffer from misalignment of the local electric field in the gap with the in-plane transition dipole moment of monolayer TMDCs. Here, we circumvent this problem by utilizing gold bi-pyramids (BPs) as very efficient plasmonic nanoantennas. We demonstrate strong coupling between individual BPs and tungsten diselenide (WSe2) monolayers at room temperature. We further study the coupling between multilayers of WSe2and BPs to elucidate the effect of the number of layers on the coupling strength. Importantly, BPs adopt a reduced-symmetry configuration when deposited on WSe2, such that only one sharp antenna tip efficiently interacts with excitons. Despite the small interaction area, we manage to achieve strong coupling, with Rabi splitting exceeding ∼100 meV. Our results suggest a feasible way toward realizing plasmon-exciton polaritons involving nanoscopic areas of TMDCs, thus pointing toward quantum and nonlinear optics applications at ambient conditions.
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| 44. |
- Tiguntseva, Ekaterina, et al.
(författare)
-
Room-Temperature Lasing from Mie-Resonant Nonplasmonic Nanoparticles
- 2020
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 14:7, s. 8149-8156
-
Tidskriftsartikel (refereegranskat)abstract
- Subwavelength particles supporting Mie resonances underpin a strategy in nanophotonics for efficient control and manipulation of light by employing both an electric and a magnetic optically induced multipolar resonant response. Here, we demonstrate that monolithic dielectric nanoparticles made of CsPbBr3 halide perovskites can exhibit both efficient Mie-resonant lasing and structural coloring in the visible and near-IR frequency ranges. We employ a simple chemical synthesis with nearly epitaxial quality for fabricating subwavelength cubes with high optical gain and demonstrate single-mode lasing governed by the Mie resonances from nanocubes as small as 310 nm by the side length. These active nanoantennas represent the most compact room-temperature nonplasmonic nanolasers demonstrated until now.
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| 45. |
- Tiguntseva, Ekaterina Y., et al.
(författare)
-
Tunable Hybrid Fano Resonances in Halide Perovskite Nanoparticles
- 2018
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 18:9, s. 5522-5529
-
Tidskriftsartikel (refereegranskat)abstract
- © 2018 American Chemical Society. Halide perovskites are known to support excitons at room temperatures with high quantum yield of luminescence that make them attractive for all-dielectric resonant nanophotonics and meta-optics. Here we report the observation of broadly tunable Fano resonances in halide perovskite nanoparticles originating from the coupling of excitons to the Mie resonances excited in the nanoparticles. Signatures of the photon-exciton ("hybrid") Fano resonances are observed in dark-field spectra of isolated nanoparticles, and also in the extinction spectra of aperiodic lattices of such nanoparticles. In the latter case, chemical tunability of the exciton resonance allows reversible tuning of the Fano resonance across the 100 nm bandwidth in the visible frequency range, providing a novel approach to control optical properties of perovskite nanostructures. The proposed method of chemical tuning paves the way to an efficient control of emission properties of on-chip-integrated light-emitting nanoantennas.
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| 46. |
|
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| 47. |
- Verre, Ruggero, 1985, et al.
(författare)
-
Transition metal dichalcogenide nanodisks as high-index dielectric Mie nanoresonators
- 2019
-
Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 14:7, s. 679-683
-
Tidskriftsartikel (refereegranskat)abstract
- Monolayer transition metal dichalcogenides (TMDCs) have recently been proposed as an excitonic platform for advanced optical and electronic functionalities 1–3 . However, in spite of intense research efforts, it has not been widely appreciated that TMDCs also possess a high refractive index 4,5 . This characteristic opens up the possibility to utilize them to construct resonant nanoantennas based on subwavelength geometrical modes 6,7 . Here, we show that nanodisks, fabricated from exfoliated multilayer WS 2 , support distinct Mie resonances and anapole states 8 that can be tuned in wavelength over the visible and near-infrared range by varying the nanodisk size and aspect ratio. As a proof of concept, we demonstrate a novel regime of light–matter interaction—anapole-exciton polaritons—which we realize within a single WS 2 nanodisk. We argue that the TMDC material anisotropy and the presence of excitons enrich traditional nanophotonics approaches based on conventional high-index materials and/or plasmonics.
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| 48. |
- Voronin, Kirill, et al.
(författare)
-
Single-Handedness Chiral Optical Cavities
- 2022
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Geometrical chirality is a universal property encountered on very different length scales ranging from geometrical shapes of living organisms to drug and DNA molecules. The interaction of chiral matter with chiral light, that is, an electromagnetic field possessing a certain handedness, underlies our ability to discriminate enantiomers of chiral molecules. In this context, it is often desired to have an optical cavity that efficiently couples to only a specific (right or left) molecular enantiomer and does not couple to the opposite one. Here, we demonstrate a single-handedness chiral optical cavity supporting only an eigenmode of a given handedness and lacking modes having the opposite one. Resonant excitation of the cavity with light of appropriate handedness enables the formation of a chiral standing wave with a uniform chirality density, while the light of opposite handedness does not cause any resonant effects. Furthermore, only chiral emitters of the matching handedness efficiently interact with such a chiral eigenmode, enabling the handedness-selective strength of light-matter coupling. The proposed system expands the set of tools available for investigations of chiral matter and opens the door to studies of a chiral electromagnetic vacuum.
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| 49. |
- Wersäll, Martin, 1985, et al.
(författare)
-
Correlative Dark-Field and Photoluminescence Spectroscopy of Individual Plasmon-Molecule Hybrid Nanostructures in a Strong Coupling Regime
- 2019
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 6:10, s. 2570-2576
-
Tidskriftsartikel (refereegranskat)abstract
- Light-matter interactions play a crucial role in several prominent nano-optical phenomena, such as plasmon-mediated fluorescence, nanoscale lasing, and strong plasmon-exciton coupling. The latter holds promise for the development of nanoscale nonlinear optical schemes and room-temperature polaritonic lasers. In recent years, strong coupling in nanoscale plasmon-exciton systems, also known as plasmon-exciton polaritons, has been thoroughly investigated using transmission, reflection, and dark-field scattering spectroscopies. However, only a few recent studies performed experiments using photoluminescence spectroscopy on the individual hybrid nanostructure level. The latter is important for the detailed understanding of intrinsic excited state dynamics in strongly coupled systems. Here, we use correlative dark-field scattering (DF) and photoluminescence (PL) measurements to study polaritonic states in individual silver nanoprisms surrounded by molecular J-aggregates. We investigate these systems under various experimental conditions, including temperatures in the range T = 4-300 K, laser excitation wavelengths at 532, 568, and 640 nm, and a broad range of plasmon-exciton detunings. Our findings indicate that the lower energy peak in PL emission closely follows the lower polariton band observed in DF, while the higher energy PL peak follows the emission of uncoupled J-aggregate molecules and incoherent states. These observations further improve the understanding of excited state dynamics in strongly coupled plasmon-exciton systems.
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| 50. |
- Yankovich, Andrew, 1983, et al.
(författare)
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Visualizing Spatial Variations of Plasmon-Exciton Polaritons at the Nanoscale Using Electron Microscopy
- 2019
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 19:11, s. 8171-8181
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Tidskriftsartikel (refereegranskat)abstract
- Polaritons are compositional light-matter quasiparticles that have enabled remarkable breakthroughs in quantum and nonlinear optics, as well as in material science. Recently, plasmon-exciton polaritons (plexcitons) have been realized in hybrid material systems composed of transition metal dichalcogenide (TMDC) materials and metal nanoparticles, expanding polaritonic concepts to room temperature and nanoscale systems that also benefit from the exotic properties of TMDC materials. Despite the enormous progress in understanding TMDC-based plexcitons using optical-based methods, experimental evidence of plexcitons formation has remained indirect and mapping their nanometer-scale characteristics has remained an open challenge. Here, we demonstrate that plexcitons generated by a hybrid system composed of an individual silver nanoparticle and a few-layer WS2 flake can be spectroscopically mapped with nanometer spatial resolution using electron energy loss spectroscopy in a scanning transmission electron microscope. Experimental anticrossing measurements using the absorption-dominated extinction signal provide the ultimate evidence for plexciton hybridization in the strong coupling regime. Spatially resolved EELS maps reveal the existence of unexpected nanoscale variations in the deep-subwavelength nature of plexcitons generated by this system. These findings pioneer new possibilities for in-depth studies of the local atomic structure dependence of polariton-related phenomena in TMDC hybrid material systems with nanometer spatial resolution.
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