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Maximizing the quality factor to mode volume ratio for ultra-small photonic crystal cavities
摘要： Small manufacturing-tolerant photonic crystal cavities are systematically designed using topology optimization to enhance the ratio between the quality factor and mode volume, Q/V. For relaxed manufacturing tolerance, a cavity with a bow-tie shape is obtained which confines light beyond the diffraction limit into a deep-subwavelength volume. Imposition of a small manufacturing tolerance still results in efficient designs, however, with diffraction-limited confinement. Inspired by numerical results, an elliptic ring grating cavity concept is extracted via geometric fitting. Numerical evaluations demonstrate that for small sizes, topology-optimized cavities enhance the Q/V-ratio by up to two orders of magnitude relative to standard L1 cavities and more than one order of magnitude relative to shape-optimized L1 cavities. An increase in cavity size can enhance the Q/V-ratio by an increase in the Q-factor without a significant increase in V. Comparison between optimized and reference cavities illustrates that significant reduction of V requires big topological changes in the cavity.
关键词： topology optimization,mode volume,light-matter interaction,photonic crystal cavities,quality factor
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Ultrastrong coupling of plasmonic metamaterials and photons in a terahertz photonic crystal cavity
摘要： Light-matter interaction in the strong coupling regime is of profound interest for fundamental quantum optics and applications. Here, we report a new type of strong light-matter interaction of metamaterial ‘quasi-particles’ with photons in a photonic crystal cavity in the terahertz frequency range. The measured Rabi splitting shows a square-root dependence on the density of metamaterial unit cells, even for unit cells from two spatially separated planar metamaterials, indicating nonlocal collective strong interactions. These findings are of interest for the investigation of fundamental strong-coupling phenomena, but also for applications such as ultra-low-threshold terahertz polariton lasing, voltage-controlled modulators and frequency filters, and ultra-sensitive chemical and biological sensing.
关键词： strong coupling,light-matter interaction,metamaterial,nonlocal collective strong interactions,terahertz,Rabi splitting,photonic crystal cavity
更新于2025-09-12 10:27:22
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Quantum light-matter interaction and controlled phonon scattering in a photonic Fano cavity
摘要： By using a Fano resonance as one of the mirrors in an optical cavity, a localized mode with a highly asymmetric line shape is obtained. Placing a single quantum emitter inside the cavity leads to a new regime of cavity quantum electrodynamics, where the light-matter interaction dynamics is fundamentally different from that observed in a conventional cavity with Lorenztian line shape. Furthermore, when the vibrational dynamics of the emitter is taken into account, an intricate phonon-photon interplay arises, and the optical interference induced by the Fano mirror signi?cantly alters the leakage of energy into vibrational modes. We demonstrate that this control mechanism improves the maximum attainable indistinguishability of emitted photons, as compared to an equivalent cavity with a conventional mirror.
关键词： phonon scattering,Quantum light-matter interaction,Fano cavity,photonic Fano cavity,cavity quantum electrodynamics
更新于2025-09-12 10:27:22
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Enhanced light-matter interaction in an atomically thin semiconductor coupled with dielectric nano-antennas
摘要： Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having the optical mode volume close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSe2. We observe a photoluminescence enhancement exceeding 104 compared with WSe2 placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 103. Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
关键词： atomically thin semiconductor,light-matter interaction,Raman scattering,dielectric nano-antennas,photoluminescence enhancement
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Coherent Coupling of Single Molecules to Microresonators
摘要： Many interesting proposals in quantum optics and light-matter interaction rely on having multiple quantum emitters well-coupled to a single mode of light. Of particular interest are cases where several identical emitters couple to a one-dimensional (1D) photonic medium. Recently, we presented such a system by evanescent coupling of organic dye molecules to the same guided mode of an on-chip subwavelength waveguide [1]. While this coupling allowed us to demonstrate up to 7.5% transmission extinction of the propagating light by a single molecule, it is still not sufficient for achieving higher-order effects such as photon-mediated interaction of multiple emitters coupled to the same waveguide. One way to improve the waveguide-emitter coupling is the use of resonant structures, as was recently shown in our laboratory for a microscopic open Fabry-Perot cavity [2]. In that work, we demonstrated a strong Purcell broadening of the molecular emission, and almost complete extinction of the resonant cavity transmission. In the current work, we extended this approach to on-chip racetrack resonators [3], as shown in Fig. 1(a). In such a geometry, the coupling enhancement is proportional to the number of photon round trips inside the resonator, which is roughly equal to F/π, where F is the resonator finesse. Currently, our resonators can reach finesse as high as 18 when exposed to the surrounding organic matrix at cryogenic temperatures, leading to enhanced extinction dips up to 22%, as shown in the orange plot in Fig. 1(b). We additionally verify the molecule-resonator coupling by localizing the position of the molecule (marked by a white arrow in Fig. 1(a)), and by observing the expected peak in the transmission port of the resonator (blue line in Fig. 1(b)). Finally, we perform a comparison to a single waveguide on the same chip, which still showed maximal extinction of only 7%, consistent with the previous results. We discuss the observed degree of enhancement, compare it with the predictions of theoretical calculations, and evaluate future strategies for reaching on-chip near-unity coupling efficiency as well as many-emitter effects, such as light localization and generation of polaritonic states [4].
关键词： racetrack resonators,light-matter interaction,waveguide-emitter coupling,photonic medium,quantum optics,Purcell broadening,polaritonic states,resonant structures,Fabry-Perot cavity,quantum emitters
更新于2025-09-12 10:27:22
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Two‐Dimensional GeP‐Based Broad‐Band Optical Switches and Photodetectors
摘要： Germanium phosphide (GeP), a typical 2D group IV–V semiconductor, has attracted significant attention due to the advantages of higher thermodynamic stability than black phosphorus (BP), widely tunable bandgap, high carrier mobility, and in-plane anisotropy. However, its photonic and optoelectronic properties have not been extensively explored so far. Herein, large size and high-quality GeP single bulk crystal is successfully grown by flux method and stripped into 2D nanosheets with liquid phase exfoliation (LPE) and spin-coating methods. The broad-band photonic and optoelectronic properties of 2D GeP nanosheets are systematically investigated. First principles calculations are performed to verify its widely tunable bandgap from 0.43 eV for bulk to 1.58 eV for monolayer. The ultrafast carrier dynamic and non-linear optical responses are investigated by non-degenerated pump-probe and open-aperture Z-scan methods, and the results indicate that 2D GeP nanosheets can present excellent broad-band saturable absorption properties. Furthermore, the 2D GeP nanosheets-based broad-band saturable absorbers (SAs) and photodetectors are demonstrated. The results indicate that 2D GeP nanosheets can be used as excellent broad-band optical modulators and detectors, which will arouse a considerable interest in exploring novel group IV–V 2D materials for broad-band photonic and optoelectronic applications.
关键词： GeP,photonic and optoelectronic devices,2D materials,light–matter interaction
更新于2025-09-12 10:27:22
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Plasmonic hotspot in toroidal metamaterial
摘要： Toroidal dipole resonance under a normal incident excitation can be realized by designing a metallic circular groove with a depth asymmetry. Due to its specific radial charge current configuration, charges gather together on the central circular platform and form a plasmonic hotspot, covering a large circular region with a diameter of 200 nm, where E-field magnitude attains 34-time enhancement than that of the incident light, providing more potentials for energy harvesting or nanoparticle trapping, manipulating of light-matter interaction, and optical data storage.
关键词： toroidal dipole resonance,Plasmonic hotspot,energy harvesting,nanoparticle trapping,light-matter interaction,optical data storage,toroidal metamaterial
更新于2025-09-11 14:15:04
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Bioinspired Toolkit Based on Intermolecular Encoder toward Evolutionary 4D Chiral Plasmonic Materials
摘要： Over the last two decades, nanophotonics, including plasmonics and metamaterials, have promised compelling opportunities for exotic control over light?matter interactions. The strong chiral light?matter interaction is a representative example. Three-dimensional (3D) chirality has existed naturally only in organic molecules and bio-organisms, but a negligible chiroptic effect was attained with these naturally occurring materials because of their small absorption cross sections. However, inspired by biological chirality, nanophotonic chiral materials have greatly expanded the design space of accessible chiroptic effects (e.g., pushing the chiral light?matter interaction to an exceptional regime, such as a broad-band circular polarizer, negative refractive index, and sensitive chiral sensing). Nevertheless, it is still a challenge to achieve precisely defined and dynamically reconfigurable chiral morphologies that further increase the chiroptic effect.
关键词： plasmonics,metamaterials,chiroptic effects,nanophotonics,chiral light?matter interaction,3D chirality
更新于2025-09-11 14:15:04
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Spontaneous and stimulated radiative emission of modulated free-electron quantum wavepackets—semiclassical analysis
摘要： Here we present a semiclassical analysis of spontaneous and stimulated radiative emission from unmodulated and optically-modulated free-electron quantum wavepackets. We show that the radiative emission/absorption and corresponding deceleration/acceleration of the wavepackets depend on the controllable ‘history-dependent’ wavepacket size. The characteristics of the radiative interaction when the wavepacket size (duration) is short relative to the radiation wavelength, are close to the predictions of the classical point-particle modelling. On the other hand, in the long-sized wavepacket limit, the interaction is quantum-mechanical, and it diminishes exponentially at high frequency. We exemplify these effects through the scheme of Smith-Purcell radiation, and demonstrate that if the wavepacket is optically-modulated and periodically-bunched, it exhibits ?nite radiative emission at harmonics of the modulation frequency beyond the limit of high-frequency cutoff. Besides, the radiation analysis is further extended to the cases of superradiant emission from a beam of phase-correlated modulated electron wavepackets. The features of the wavepacket-dependent radiative emission explain the classical-to-quantum transition, and indicate a way for measuring the quantum electron wavepacket size. This suggests a new direction for exploring light–matter interaction.
关键词： radiative emission,light–matter interaction,wavepacket-dependent radiative emission
更新于2025-09-09 09:28:46
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Fano Resonance Generation and Applications in 3D Folding Metamaterials
摘要： The development of nanotechnology has endowed the light-matter interaction with more degrees of freedom, and made the manipulation of optical phenomena more precise and arbitrary. Fano resonance is a type of resonant scattering phenomenon with asymmetric line profile, which was firstly studied in atomic physics and then introduced to photonics and plasmonics. This phenomenon is due to the interference between a discrete bound state and a continuum state, thus a two-body or few-body system is needed to provide different types of states that are necessary in this phenomenon. Artificial metamaterial is a very good candidate to generate Fano resonances because of its designable configuration. In this paper, a new type of structure—3D folding metamaterial—is introduced for Fano resonance generation and application. The structure, fabricated by focused-ion-beam based folding technique, is composed of planar and out-of-plane parts, which are essential for the excitation of the discrete bound states and continuum states. The intensity, frequency and quality factor of the Fano resonances can be modulated by the configuration of the 3D folding structures (shape, size, inclined angle, etc.), thus enlarges its application potential such as index sensing and surface enhanced Raman scattering.
关键词： 3D folding metamaterial,nanotechnology,Fano resonance,surface enhanced Raman scattering,light-matter interaction
更新于2025-09-09 09:28:46