Ultranarrow and Tunable Fano Resonance in Ag Nanoshells and a Simple Ag Nanomatryushka

We study theoretically the Fano resonances (FRs) produced by the near-field coupling between the lowest-order (dipolar) sphere plasmon resonance and the dipolar cavity plasmon mode supported by an Ag nanoshell or the hybrid mode in a simple three-layered Ag nanomatryushka constructed by incorporating a solid Ag nanosphere into the center of Ag nanoshell. We find that the linewidth of dipolar cavity plasmon resonance or hybrid mode induced FR is as narrow as 6.8 nm (corresponding to a high Q-factor of ~160 and a long dephasing time of ~200 fs) due to the highly localized feature of the electric-fields. In addition, we attribute the formation mechanisms of typical asymmetrical Fano line profiles in the extinction spectra to the constructive (Fano peak) and the destructive interferences (Fano dip) arising from the symmetric and asymmetric charge distributions between the dipolar sphere and cavity plasmon or hybrid modes. Interestingly, by simply adjusting the structural parameters, the dielectric refractive index required for the strongest FR in the Ag nanomatryushka can be reduced to be as small as 1.4, which largely reduces the restriction on materials, and the positions of FR can also be easily tuned across a broad spectral range. The ultranarrow linewidth, highly tunability together with the huge enhancement of electric fields at the FR may find important applications in sensing, slow light, and plasmon rulers.

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Measurement of the Near Field Distribution of a Microwave Horn Using a Resonant Atomic Probe

Applied Sciences ◽

10.3390/app9224895 ◽

2019 ◽

Vol 9 (22) ◽

pp. 4895 ◽

Cited By ~ 1

Author(s):

Jingxu Bai ◽

Jiabei Fan ◽

Liping Hao ◽

Nicholas L. R. Spong ◽

Yuechun Jiao ◽

...

Keyword(s):

Field Distribution ◽

Electric Fields ◽

Microwave Field ◽

Electric Field Distribution ◽

Near Field ◽

Field Measurements ◽

Amplitude Distribution ◽

Field Coupling ◽

All Optical ◽

Atomic Probe

We measure the near field distribution of a microwave horn with a resonant atomic probe. The microwave field emitted by a standard microwave horn is investigated utilizing Rydberg electromagnetically inducted transparency (EIT), an all-optical Rydberg detection, in a room temperature caesium vapor cell. The ground 6 S 1 / 2 , excited 6 P 3 / 2 , and Rydberg 56 D 5 / 2 states constitute a three-level system, used as an atomic probe to detect microwave electric fields by analyzing microwave dressed Autler–Townes (AT) splitting. We present a measurement of the electric field distribution of the microwave horn operating at 3.99 GHz in the near field, coupling the transition 56 D 5 / 2 → 57 P 3 / 2 . The microwave dressed AT spectrum reveals information on both the strength and polarization of the field emitted from the microwave horn simultaneously. The measurements are compared with field measurements obtained using a dipole metal probe, and with simulations of the electromagnetic simulated software (EMSS). The atomic probe measurement is in better agreement with the simulations than the metal probe. The deviation from the simulation of measurements taken with the atomic probe is smaller than the metal probe, improving by 1.6 dB. The symmetry of the amplitude distribution of the measured field is studied by comparing the measurements taken on either side of the field maxima.

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Ultra Narrow Dual-Band Perfect Absorber Based on a Dielectric−Dielectric−Metal Three-Layer Film Material

Micromachines ◽

10.3390/mi12121552 ◽

2021 ◽

Vol 12 (12) ◽

pp. 1552

Author(s):

Bin Liu ◽

Pinghui Wu ◽

Hongyang Zhu ◽

Li Lv

Keyword(s):

Plasmon Resonance ◽

Near Infrared ◽

Incident Angle ◽

Structural Parameters ◽

Dual Band ◽

Refractive Index Sensor ◽

Perfect Absorber ◽

Film Material ◽

High Q ◽

Magnetic Polaritons

This paper proposes a perfect metamaterial absorber based on a dielectric−dielectric−metal structure, which realizes ultra-narrowband dual-band absorption in the near-infrared band. The maximum Q factor is 484. The physical mechanism that causes resonance is hybrid coupling between magnetic polaritons resonance and plasmon resonance. At the same time, the research results show that the intensity of magnetic polaritons resonance is much greater than the intensity of the plasmon resonance. By changing the structural parameters and the incident angle of the light source, it is proven that the absorber is tunable, and the working angle tolerance is 15°. In addition, the sensitivity and figure of merit when used as a refractive index sensor are also analyzed. This design provides a new idea for the design of high-Q optical devices, which can be applied to photon detection, spectral sensing, and other high-Q multispectral fields.

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Transition to strong coupling regime in hybrid plasmonic systems: exciton-induced transparency and Fano interference

Nanophotonics ◽

10.1515/nanoph-2021-0246 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Tigran V. Shahbazyan

Keyword(s):

Strong Coupling ◽

Energy Exchange ◽

Near Field ◽

Plasmon Mode ◽

Strong Coupling Regime ◽

Field Coupling ◽

Fano Interference ◽

Scattering Spectra ◽

Spectral Asymmetry ◽

Induced Transparency

Abstract We present a microscopic model describing the transition to a strong coupling regime for an emitter resonantly coupled to a surface plasmon in a metal–dielectric structure. We demonstrate that the shape of scattering spectra is determined by an interplay of two distinct mechanisms. First is the near-field coupling between the emitter and the plasmon mode which underpins energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra prior to the transition to a strong coupling regime. The second mechanism is the Fano interference between the plasmon dipole and the plasmon-induced emitter’s dipole as the system interacts with the radiation field. We show that the Fano interference can strongly affect the overall shape of scattering spectra, leading to the inversion of spectral asymmetry that was recently reported in the experiment.

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Graphene-Modulated Terahertz Metasurfaces for Selective and Active Control of Dual-Band Electromagnetic Induced Reflection (EIR) Windows

Nanomaterials ◽

10.3390/nano11092420 ◽

2021 ◽

Vol 11 (9) ◽

pp. 2420

Author(s):

Xunjun He ◽

Chenguang Sun ◽

Yue Wang ◽

Guangjun Lu ◽

Jiuxing Jiang ◽

...

Keyword(s):

Active Control ◽

Slow Light ◽

Near Field ◽

Dual Band ◽

Destructive Interference ◽

Dark Mode ◽

Field Coupling ◽

Control Scheme ◽

Electrostatic Doping ◽

Induced Transparency

Currently, metasurfaces (MSs) integrating with different active materials have been widely explored to actively manipulate the resonance intensity of multi-band electromagnetic induced transparency (EIT) windows. Unfortunately, these hybrid MSs can only realize the global control of multi-EIT windows rather than selective control. Here, a graphene-functionalized complementary terahertz MS, composed of a dipole slot and two graphene-integrated quadrupole slots with different sizes, is proposed to execute selective and active control of dual-band electromagnetic induced reflection (EIR) windows. In this structure, dual-band EIR windows arise from the destructive interference caused by the near field coupling between the bright dipole slot and dark quadrupole slot. By embedding graphene ribbons beneath two quadrupole slots, the resonance intensity of two windows can be selectively and actively modulated by adjusting Fermi energy of the corresponding graphene ribbons via electrostatic doping. The theoretical model and field distributions demonstrate that the active tuning behavior can be ascribed to the change in the damper factor of the corresponding dark mode. In addition, the active control of the group delay is further investigated to develop compact slow light devices. Therefore, the selective and active control scheme introduced here can offer new opportunities and platforms for designing multifunctional terahertz devices.

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Lattice Plasmon Mode Excitation via Near Field Coupling

Chinese Physics B ◽

10.1088/1674-1056/ac0523 ◽

2021 ◽

Author(s):

Yun Lin ◽

Shuo Shen ◽

Xiang Gao ◽

Liancheng Wang

Keyword(s):

Near Field ◽

Plasmon Mode ◽

Field Coupling ◽

Mode Excitation

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Independently tunable electromagnetically induced transparency effect and dispersion in a multi-band terahertz metamaterial

Scientific Reports ◽

10.1038/s41598-019-54414-5 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 8

Author(s):

Rakesh Sarkar ◽

Dipa Ghindani ◽

Koijam Monika Devi ◽

S. S. Prabhu ◽

Amir Ahmad ◽

...

Keyword(s):

Slow Light ◽

Electromagnetically Induced Transparency ◽

Near Field ◽

The Other ◽

Transmission Spectra ◽

Field Coupling ◽

Induced Transparency ◽

Coupled Harmonic Oscillator ◽

Bright Mode ◽

Multi Band

AbstractIn this article, we experimentally and numerically investigate a planar terahertz metamaterial (MM) geometry capable of exhibiting independently tunable multi-band electromagnetically induced transparency effect (EIT). The MM structure exhibits multi-band EIT effect due to the strong near field coupling between the bright mode of the cut-wire (CW) and dark modes of pair of asymmetric double C resonators (DCRs). The configuration allows us to independently tune the transparency windows which is challenging task in multiband EIT effect. The independent modulation is achieved by displacing one DCR with respect to the CW, while keeping the other asymmetric DCR fixed. We further examine steep dispersive behavior of the transmission spectra within the transparency windows and analyze slow light properties. A coupled harmonic oscillator based theoretical model is employed to elucidate as well as understand the experimental and numerical observations. The study can be highly significant in the development of multi-band slow light devices, buffers and modulators.

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Multiple Sharp Fano Resonances in a Deep-Subwavelength Spherical Hyperbolic Metamaterial Cavity

Nanomaterials ◽

10.3390/nano11092301 ◽

2021 ◽

Vol 11 (9) ◽

pp. 2301

Author(s):

Ping Gu ◽

Yuheng Guo ◽

Jing Chen ◽

Zuxing Zhang ◽

Zhendong Yan ◽

...

Keyword(s):

Electric Fields ◽

Near Field ◽

Energy Difference ◽

Fano Resonances ◽

Hyperbolic Metamaterial ◽

Whispering Gallery ◽

Field Coupling ◽

Dielectric Layers ◽

Potential Applications ◽

Plasmon Modes

We theoretically study the multiple sharp Fano resonances produced by the near-field coupling between the multipolar narrow plasmonic whispering-gallery modes (WGMs) and the broad-sphere plasmon modes supported by a deep-subwavelength spherical hyperbolic metamaterial (HMM) cavity, which is constructed by five alternating silver/dielectric layers wrapping a dielectric nanosphere core. We find that the linewidths of WGMs-induced Fano resonances are as narrow as 7.4–21.7 nm due to the highly localized feature of the electric fields. The near-field coupling strength determined by the resonant energy difference between WGMs and corresponding sphere plasmon modes can lead to the formation of the symmetric-, asymmetric-, and typical Fano lineshapes in the far-field extinction efficiency spectrum. The deep-subwavelength feature of the proposed HMM cavity is verified by the large ratio (~5.5) of the longest resonant wavelength of WGM1,1 (1202.1 nm) to the cavity size (diameter: 220 nm). In addition, the resonant wavelengths of multiple Fano resonances can be easily tuned by adjusting the structural/material parameters (the dielectric core radius, the thickness and refractive index of the dielectric layers) of the HMM cavity. The narrow linewidth, multiple, and tunability of the observed Fano resonances, together with the deep-subwavelength feature of the proposed HMM cavity may create potential applications in nanosensors and nanolasers.

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Multiband transparency effect induced by toroidal excitation in a strongly coupled planar terahertz metamaterial

Scientific Reports ◽

10.1038/s41598-021-98498-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Angana Bhattacharya ◽

Rakesh Sarkar ◽

Naval K. Sharma ◽

Bhairov K. Bhowmik ◽

Amir Ahmad ◽

...

Keyword(s):

Coupled Oscillators ◽

Ring Resonator ◽

Near Field ◽

Split Ring Resonator ◽

Split Ring ◽

Strongly Coupled ◽

Future Studies ◽

High Q ◽

Field Coupling ◽

Sensing Applications

AbstractThe multiband transparency effect in terahertz (THz) domain has intrigued the scientific community due to its significance in developing THz multiband devices. In this article, we have proposed a planar metamaterial geometry comprised of a toroidal split ring resonator (TSRR) flanked by two asymmetric C resonators. The proposed geometry results in multi-band transparency windows in the THz region via strong near field coupling of the toroidal excitation with the dipolar C-resonators of the meta molecule. The geometry displays dominant toroidal excitation as demonstrated by a multipolar analysis of scattered radiation. High Q factor resonances of the metamaterial configuration is reported which can find significance in sensing applications. We report the frequency modulation of transparency windows by changing the separation between TSRR and the C resonators. The numerically simulated findings have been interpreted and validated using an equivalent theoretical model based upon three coupled oscillators system. Such modeling of toroidal resonances may be utilized in future studies on toroidal excitation based EIT responses in metamaterials. Our study has the potential to impact the development of terahertz photonic components useful in building next generation devices.

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High-Q dark hyperbolic phonon-polaritons in hexagonal boron nitride nanostructures

Nanophotonics ◽

10.1515/nanoph-2020-0048 ◽

2020 ◽

Vol 9 (6) ◽

pp. 1457-1467 ◽

Cited By ~ 1

Author(s):

Georg Ramer ◽

Mohit Tuteja ◽

Joseph R. Matson ◽

Marcelo Davanco ◽

Thomas G. Folland ◽

...

Keyword(s):

Boron Nitride ◽

Cross Sections ◽

Hexagonal Boron Nitride ◽

Near Field ◽

High Q ◽

Surface Phonon Polaritons ◽

Previous Hypothesis ◽

Phonon Polaritons ◽

Field Reflectance ◽

Strong Confinement

AbstractThe anisotropy of hexagonal boron nitride (hBN) gives rise to hyperbolic phonon-polaritons (HPhPs), notable for their volumetric frequency-dependent propagation and strong confinement. For frustum (truncated nanocone) structures, theory predicts five, high-order HPhPs, sets, but only one set was observed previously with far-field reflectance and scattering-type scanning near-field optical microscopy. In contrast, the photothermal induced resonance (PTIR) technique has recently permitted sampling of the full HPhP dispersion and observing such elusive predicted modes; however, the mechanism underlying PTIR sensitivity to these weakly-scattering modes, while critical to their understanding, has not yet been clarified. Here, by comparing conventional contact- and newly developed tapping-mode PTIR, we show that the PTIR sensitivity to those weakly-scattering, high-Q (up to ≈280) modes is, contrary to a previous hypothesis, unrelated to the probe operation (contact or tapping) and is instead linked to PTIR ability to detect tip-launched dark, volumetrically-confined polaritons, rather than nanostructure-launched HPhPs modes observed by other techniques. Furthermore, we show that in contrast with plasmons and surface phonon-polaritons, whose Q-factors and optical cross-sections are typically degraded by the proximity of other nanostructures, the high-Q HPhP resonances are preserved even in high-density hBN frustum arrays, which is useful in sensing and quantum emission applications.

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Atomic 2D electric field imaging of a Yagi–Uda antenna near-field using a portable Rydberg-atom probe and measurement instrument

Advanced Optical Technologies ◽

10.1515/aot-2020-0029 ◽

2020 ◽

Vol 9 (5) ◽

pp. 305-312

Author(s):

Ryan Cardman ◽

Luís F. Gonçalves ◽

Rachel E. Sapiro ◽

Georg Raithel ◽

David A. Anderson

Keyword(s):

Electric Field ◽

Electric Fields ◽

Field Measurement ◽

Near Field ◽

Measurement Instrument ◽

Rydberg Atom ◽

Field Measurements ◽

Atom Probe ◽

Electric Field Measurement ◽

Measurement Uncertainties

AbstractWe present electric field measurements and imaging of a Yagi–Uda antenna near-field using a Rydberg atom–based radio frequency electric field measurement instrument. The instrument uses electromagnetically induced transparency with Rydberg states of cesium atoms in a room-temperature vapor and off-resonant RF-field–induced Rydberg-level shifts for optical SI-traceable measurements of RF electric fields over a wide amplitude and frequency range. The electric field along the antenna boresight is measured using the atomic probe at a spatial resolution of ${\lambda }_{RF}/2$ with electric field measurement uncertainties below 5.5%, an improvement to RF measurement uncertainties provided by existing antenna standards.

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