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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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Unveiling the radiative local density of optical states of a plasmonic nanocavity by STM
摘要： Atomically-sharp tips in close proximity of metal surfaces create plasmonic nanocavities supporting both radiative (bright) and non-radiative (dark) localized surface plasmon modes. Disentangling their respective contributions to the total density of optical states remains a challenge. Electroluminescence due to tunnelling through the tip-substrate gap could allow the identification of the radiative component, but this information is inherently convoluted with that of the electronic structure of the system. In this work, we present a fully experimental procedure to eliminate the electronic-structure factors from the scanning tunnelling microscope luminescence spectra by confronting them with spectroscopic information extracted from elastic current measurements. Comparison against electromagnetic calculations demonstrates that this procedure allows the characterization of the meV shifts experienced by the nanocavity plasmonic modes under atomic-scale gap size changes. Therefore, the method gives access to the frequency-dependent radiative Purcell enhancement that a microscopic light emitter would undergo when placed at such nanocavity.
关键词： scanning tunnelling microscope luminescence,plasmonic nanocavities,local density of optical states,radiative Purcell enhancement
更新于2025-09-23 15:21:01
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Brightening and Guiding Single‐Photon Emission by Plasmonic Waveguide–Slit Structures on a Metallic Substrate
摘要： By designing a plasmonic waveguide–slit structure (a nanoslit etched in a silver nanowire) on a silver substrate, an ultrahigh Purcell factor and ultralarge figure of merit (FOM) are numerically predicted. Because of the large field enhancement (>150 times the incident field) and the ultrasmall optical volume (V ≈ 2 × 10?5λ3) of the resonant mode in the metallic nanoslit, the simulations show that the Purcell factor in the system can reach up to FP = 1.68 × 105, which is more than ten times the maximum Purcell factor in previous work (by placing metallic nanoparticles on a metal surface with a nanogap). Because of the utilization of a silver substrate rather than the common dielectric substrate, the mode cutoff of the surface plasmon polariton (SPP) waveguide mode is completely eliminated, which provides a large selection range of the nanowire radii to support the resonant mode in the nanoslit. Moreover, the SPP propagation length is significantly increased by more than 30 times. As a result, an ultralarge FOM of 1.40 × 107 is obtained, which is more than 80 times the maximum FOM in previous work where the metallic nanowire is placed on or surrounded by dielectric materials.
关键词： efficient guiding,long propagation length,bright single-photon emission,metallic substrates,purcell enhancement
更新于2025-09-19 17:13:59
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Polarization-dependent light-matter coupling and highly indistinguishable resonant fluorescence photons from quantum dot-micropillar cavities with elliptical cross section
摘要： We study the optical properties of coupled quantum dot-microcavity systems with an elliptical cross section. First, we develop an analytic model that describes the spectrum of the cavity modes that are split due to the reduced symmetry of the resonator. By coupling the quantum dot (QD) emission to the polarized fundamental cavity modes, we observe the vectorial nature of the Purcell enhancement, which depends on the intrinsic polarization of the quantum dot and its relative alignment with respect to the cavity axis. The variable interaction strength of the QD with the polarized cavity modes leads to the observation of strong and weak coupling. Finally, we demonstrate the capability of elliptical micropillars to emit single and highly indistinguishable photons (visibility of 87%).
关键词： elliptical cross section,Purcell enhancement,indistinguishable photons,quantum dot,micropillar cavities,strong and weak coupling
更新于2025-09-12 10:27:22