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Manipulation of Magnetic Dipole Emission from Eu <sup>3+</sup> with Mie-Resonant Dielectric Metasurfaces
摘要： Mie-resonant high-index dielectric nanoparticles and metasurfaces have been suggested as a viable platform for enhancing both electric and magnetic dipole transitions of fluorescent emitters. While the enhancement of the electric dipole transitions by such dielectric nanoparticles has been demonstrated experimentally, the case of magnetic-dipole transitions remains largely unexplored. Here, we study the enhancement of spontaneous emission of Eu3+ ions, featuring both electric and magnetic-dominated dipole transitions, by dielectric metasurfaces composed of Mie-resonant silicon nanocylinders. By coating the metasurfaces with a layer of an Eu3+ doped polymer, we observe an enhancement of the Eu3+ emission associated with the electric (at 610 nm) and magnetic-dominated (at 590 nm) dipole transitions. The enhancement factor depends systematically on the spectral proximity of the atomic transitions to the Mie resonances as well as their multipolar order, which is controlled by the nanocylinder radius. Importantly, the branching ratio of emission via the electric or magnetic transition channel can be modified by carefully designing the metasurface, where the magnetic dipole transition is enhanced more than the electric transition for cylinders with radii of about 130 nm. We confirm our observations by numerical simulations based on the reciprocity principle. Our results open new opportunities for bright nanoscale light sources based on magnetic transitions.
关键词： Purcell enhancement,Dielectric metasurfaces,Mie resonances,Magnetic dipole emission
更新于2025-09-23 15:23:52
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Quality factor assessment of finite-size all-dielectric metasurfaces at the magnetic dipole resonance
摘要： Recently there has been a large interest in achieving metasurface resonances with large quality factors. In this article, we examine metasurfaces that comprised a finite number of magnetic dipoles oriented parallel or orthogonal to the plane of the metasurface and determine analytic formulas for their resonances’ quality factors. These conditions are experimentally achievable in finite-size metasurfaces made of dielectric cubic resonators at the magnetic dipole resonance. Our results show that finite metasurfaces made of parallel (to the plane) magnetic dipoles exhibit low quality factor resonances with a quality factor that is independent of the number of resonators. More importantly, finite metasurfaces made of orthogonal (to the plane) magnetic dipoles lead to resonances with large quality factors, which ultimately depend on the number of resonators comprising the metasurface. In particular, by properly modulating the array of dipole moments by having a distribution of resonator polarizabilities, one can potentially increase the quality factor of metasurface resonances even further. These results provide design guidelines to achieve a sought quality factor applicable to any resonator geometry for the development of new devices such as photodetectors, modulators, and sensors.
关键词： dipole approximation,Mie resonances,magnetic dipole resonance,finite-size metasurfaces,High quality factor
更新于2025-09-23 15:22:29
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Towards silicon-based metamaterials
摘要： We study periodic lattices of silicon nanorods and introduce the concept of a phase diagram that characterizes a transition between the regimes of photonic crystals and dielectric metamaterials when the lattice spacing and operational wavelength vary. We find the conditions when a hexagonal periodic lattice of silicon nanorods can operate as a metamaterial described by averaged parameters. In general, we reveal that the metamaterial regime can be achieved for dielectric permittivity exceeding the value ε = 14, being commonly available for semiconductors in both visible and near-infrared frequency ranges. Thus, advanced semiconductor technologies can offer a versatile platform for novel designs of all-dielectric Mie-resonant metadevices.
关键词： phase diagram,photonic crystals,dielectric metamaterials,Mie resonances,silicon nanorods
更新于2025-09-23 15:21:21
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Structural Colors Enabled by Lattice Resonance on Silicon Nitride Metasurfaces
摘要： Artificial color pixels based on dielectric Mie resonators are appealing for scientific research as well as practical design. Vivid colors are imperative for displays and imaging. Dielectric metasurface-based artificial pixels are promising candidates for developing flat, flexible, and/or wearable displays. Considering the application feasibility of artificial color pixels, wide color gamuts are crucial for contemporary display technology. To achieve a wide color gamut, ensuring the purity and efficiency of nanostructure resonance peaks in the visible spectrum is necessary for structural color design. Low-loss dielectric materials are suitable for achieving vivid colors with structural color pixels. However, high-order Mie resonances prevent color pixels based on dielectric metasurfaces from efficiently generating highly saturated colors. In particular, fundamental Mie resonances (electric/magnetic dipole) for red can result in not only a strong resonance peak at 650 nm, but also high-order Mie resonances at shorter wavelengths, which reduces the saturation of the target color. To address these problems, we fabricated silicon nitride metasurfaces on quartz substrates and applied Rayleigh anomalies at relatively short wavelengths to successfully suppress high-order Mie resonances, thus creating vivid color pixels. We performed numerical design, semianalytic considerations, and experimental proof-of-concept examinations to demonstrate the performance of the silicon nitride metasurfaces. Apart from traditional metasurface designs that involve transmission and reflection modes, we determined that lateral light incidence on silicon nitride metasurfaces can provide vivid colors through long-range dipole interactions; this can thus extend the applications of such surfaces to eyewear displays and guided-wave illumination techniques.
关键词： metasurfaces,Mie resonances,lattice resonances,color,silicon nitride,high-refractive-index nanostructures
更新于2025-09-23 15:19:57
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Mie Scattering in the Macroscopic Response and the Photonic Bands of Metamaterials
摘要： Herein, a general approach for the numerical calculation of the effective dielectric tensor of metamaterials is presented, and it is shown that the formalism may be used to study metamaterials beyond the long-wavelength limit. A system composed of high-refractive-index cylindrical inclusions is considered, and it is shown that the method reproduces the Mie resonant features and photonic band structure obtained from a multiple scattering approach, hence opening the possibility to study arbitrarily complex geometries for the design of resonance-based negative refractive metamaterials at optical wavelengths.
关键词： Mie resonances,nonlocal optics,metamaterials,homogenization
更新于2025-09-23 15:19:57
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Active control of anapole states by structuring the phase-change alloy Ge2Sb2Te5
摘要： High-index dielectric nanoparticles supporting a distinct series of Mie resonances have enabled a new class of optical antennas with unprecedented functionalities. The great wealth of multipolar responses has not only brought in new physical insight but also spurred practical applications. However, how to make such a colorful resonance palette actively tunable is still elusive. Here, we demonstrate that the structured phase-change alloy Ge2Sb2Te5 (GST) can support a diverse set of multipolar Mie resonances with active tunability. By harnessing the dramatic optical contrast of GST, we realize broadband (Δλ/λ ~ 15%) mode shifting between an electric dipole resonance and an anapole state. Active control of higher-order anapoles and multimodal tuning are also investigated, which make the structured GST serve as a multispectral optical switch with high extinction contrasts (>6 dB). With all these findings, our study provides a new direction for realizing active nanophotonic devices.
关键词： active tuning,nanophotonics,phase-change materials,anapole states,GST,Mie resonances
更新于2025-09-19 17:15:36
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All-Dielectric Nanoresonators for ??(2) Nonlinear Optics
摘要： Metal-less nanophotonics offers new opportunities for non-linear optics with respect to optical waveguides and microresonators, taking advantage of the progress within nanofabrication to boost the development of subwavelength Mie-type structures. Here, we review recent results on second harmonic generation with semiconductor nanoresonators, focusing on their scattering features in terms of efficiency and control over radiation patterns. First, two theoretical models are comparatively discussed with a view to possible improvements in analysis and design. Then, some relevant experiments are reported, and the origin of the χ(2) generation is discussed, outlining the main open topics to investigate in the near future and the advantages offered by these nanostructures to the development of novel photonic devices.
关键词： Mie resonances,second harmonic generation,AlGaAs nanoresonators,all-dielectric resonators,nanophotonics
更新于2025-09-19 17:13:59
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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) - Efficient Terahertz Detection with Perfectly-Absorbing Metasurface
摘要： We demonstrate a unique photoconductive design for terahertz (THz) detection based on a perfectly absorbing, all-dielectric metasurface. Our design exploits Mie resonances in electrically connected cubic resonators fabricated in low-temperature grown (LT) GaAs. Experimentally, the detector achieves very high contrast between ON/OFF conductivity states (107) whilst also requiring extremely low optical power for optimal operation (100 μW). We find that the Mie resonances dissipate sufficiently fast and maintain the detection bandwidth up to 3 THz.
关键词： photoconductive,terahertz detection,Mie resonances,LT-GaAs,metasurface
更新于2025-09-12 10:27:22
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Engineering the Charge Transport Properties of Resonant Silicon Nanoparticles in Perovskite Solar Cells
摘要： Resonant semiconductor nanoparticles (NPs) that improve both light trapping and scattering have recently emerged as an additional tool for enhancing the efficiency of perovskite solar cells. Among the various types of nanostructures, silicon NPs, which support Mie modes and have lower losses compared with metallic particles with plasmon resonances, exhibit the best improvement for standard methyl-ammonium lead iodide (MAPbI3)-based solar cells. Herein, not only the optical problem of solar cell optimization with silicon nanoantennas is studied, but also the effects related to charge carrier transport in the presence of NPs are considered. In particular, it is theoretically shown that the silicon nanoantennas can be further optimized by p-doping. The experimental verification is conducted for MAPbI3-based solar cells by p-doped silicon NPs in a hole transport layer (Spiro-OMeTAD). The improved generation rate of charge carriers and hole transport through the doped silicon NPs leads to improved efficiency of the device.
关键词： numerical modeling,perovskite solar cells,Mie resonances,silicon nanoparticles
更新于2025-09-11 14:15:04
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Second-Harmonic Generation by Mie-resonant Nanoparticles with Bulk Quadratic Nonlinearity
摘要： We study resonantly enhanced second-harmonic generation (SHG) by dielectric nanoparticles made of noncentrosymmetric materials with bulk quadratic nonlinearity. By combining analytical and numerical methods, we analyze the multipolar nature of the second-harmonic generated fields in AlGaAs and BaTiO3 nanoparticles optically excited in the vicinity of the low-order Mie resonances, with a particular focus on the magnetic dipole resonance. We derive selection rules for the multipolar composition of the nonlinear radiation depending on the symmetry of the crystalline structure and polarization of the incident light. The developed description can be instructive for design of highly-efficient nonlinear optical nanoantennas with reconfigurable radiation characteristics.
关键词： second-harmonic generation,nonlinear scattering,nanophotonics,Mie resonances,high-index nanoparticles
更新于2025-09-10 09:29:36