Different Kinds Of Resonators Research Articles

Plasmonic nanosensor based on multiple independently tunable Fano resonances.

A novel refractive index nanosensor with compound structures is proposed in this paper. It consists of three different kinds of resonators and two stubs which are side-coupled to a metal–dielectric–metal (MDM) waveguide. By utilizing numerical investigation with the finite element method (FEM), the simulation results show that the transmission spectrum of the nanosensor has as many as five sharp Fano resonance peaks. Due to their different resonance mechanisms, each resonance peak can be independently tuned by adjusting the corresponding parameters of the structure. In addition, the sensitivity of the nanosensor is found to be up to 1900 nm/RIU. For practical application, a legitimate combination of various different components, such as T-shaped, ring, and split-ring cavities, has been proposed which dramatically reduces the nanosensor dimensions without sacrificing performance. These design concepts pave the way for the construction of compact on-chip plasmonic structures, which can be widely applied to nanosensors, optical splitters, filters, optical switches, nonlinear photonic and slow-light devices.

Robust metamaterial-based antireflection coating for surface plasmon polariton resonance

A metasurface antireflection coating (meta-ARC) consisting of a gold disk array (GDA) and a dielectric layer greatly provides the flexibility to reduce the undesired reflection of light at the interface of the incident medium (air) and the surface plasmon polariton (SPP) structures such as a metallic hole array (MHA). Due to the possibility of changing the coupling strength between two different kinds of resonances (in GDA and MHA) caused by fabrication imperfections, we investigate the impacts of resonance coupling to the performance of antireflection by varying the shape of gold disks in meta-ARC and the alignment-shift between GDA and MHA. Simulation results show that (1) the amplitude of transmitted light through meta-ARC (with fabrication-induced shape-variation in GD) and MHA is only changed by small amount as compared to the meta-ARC with ideal-shaped GDs, (2) the transmission through MHA can be improved in the range of 44% (maximally alignment-shifted GDs) up to 83% (perfectly aligned GDs) by suppressing the reflected light owing to the meta-ARC, which indicates that MHA transmission light can be enhanced by more than 44% regardless of any imperfections in the fabrication of GDs while the SPP resonance wavelengths remain invariant in both cases. Our work can pave the way for a robust ARC method, leading to efficiently improving the performance of plasmonic optoelectronic devices when the meta-ARC is integrated.

Low-threshold optical bistability in a metasurface with graphene

A nonlinear metasurface made of a few-layer graphene and a metal grating is proposed in this work. It is demonstrated that the graphene plasmons can be excited in this configuration efficiently and two quite different kinds of resonances are found. The resonant behaviors and their origins are analyzed carefully, and the influences of grating groove and period on the resonances are discussed. It is surprising that the width of grating groove plays an important role in the resonant behaviors, distinct from the dielectric gratings. Due to the coupling of graphene plasmons and the grating, the highly tunability and large near field enhancement of our structure are observed. Finally, we apply our results to the optical bistability, and the low-threshold hysterical behavior with only a few MW is observed due to the large third-order nonlinear response of graphene and the strong localized field enhancement. We believe that our results will be inspiring not only for more complicated metasurfaces involving graphene, but also for other nonlinear optical applications.

On two different kinds of resonances in one-dimensional quantum-mechanical models

We apply the Riccati–Pade method and the Rayleigh–Ritz method with complex rotation to the study of the resonances of a one-dimensional well with two barriers. The model exhibits two different kinds of resonances and we calculate them by means of both approaches. While the Rayleigh–Ritz method reveals each set at a particular interval of rotation angles the Riccati–Pade method yields both of them as roots of the same Hankel determinants.

Tailoring electromagnetically induced transparency effect of terahertz metamaterials on ultrathin substrate

Electromagnetically induced transparency (EIT) is a fascinating phenomenon in optical physics and has been employed in slow light technology. In this work, we use terahertz (THz) metamaterials to mimic EIT phenomenon and study their spectral dependence on the coupling strength between bright and dark resonators. In these metamaterials, two kinds of resonators are located on two different layers separated by a 10-µm-thick polyimide (PI) film. The whole sample is supported by a 5-µm-thick flexible PI film, so the Fabry-Perot resonance at THz can be avoided. The coupling strength is tuned by the translational offset of symmetry axes between two different kinds of resonators, resulting in the change of EIT-like spectra.

Tunable Localized Resonances of Spherical Composite Particles at Optical and Near-Infrared Frequencies

We report on the design of spherical composite particles (SCPs) which consist of a homogeneous distribution of metal nano-particles (Ag) in a dielectric matrix. The effective dielectric function of SCPs is described by Maxwell–Garnett effective medium theory. Within the context of Mie scattering, the extinction efficiency of SCPs in air can be specified which exhibits two different kinds of resonances;localized surface plasmon resonances (LSPRs) and dielectric resonances (DRs). Both kinds of resonances can be tuned through the permittivity of the dielectric matrix, filling fraction of the metal nano-particles, and the radius of SCPs. The special features of the localized resonances of SCPs have the potential to be used in a wide variety of applications.

Viscous damping on flexural mechanical resonators

A new analytical formula predicting the quality factor of a wide range of flexural mechanical resonators operating in a viscous fluid medium is presented. The formula is derived from a fluid analogy used in the single beam Euler–Bernoulli bending theory, and an extension to tuning forks is proposed. Comparisons with experimental data extracted from the literature are presented. New experiments have also been carried out on different kinds of resonators to investigate the pressure dependency of their quality factors in air. In both cases, very good agreement is obtained for resonator sizes ranging from micrometric to macroscopic sizes.

Coupling between corotation and Lindblad resonances in the presence of secular precession rates

We investigate the dynamics of two satellites with masses \(\mu _s\) and \(\mu '_s\) orbiting a massive central planet in a common plane, near a first order mean motion resonance \(m+1{:}m\) (m integer). We consider only the resonant terms of first order in eccentricity in the disturbing potential of the satellites, plus the secular terms causing the orbital apsidal precessions. We obtain a two-degrees-of-freedom system, associated with the two critical resonant angles \(\phi = (m+1)\lambda ' -m\lambda - \varpi \) and \(\phi '= (m+1)\lambda ' -m\lambda - \varpi '\), where \(\lambda \) and \(\varpi \) are the mean longitude and longitude of periapsis of \(\mu _s\), respectively, and where the primed quantities apply to \(\mu '_s\). We consider the special case where \(\mu _s \rightarrow 0\) (restricted problem). The symmetry between the two angles \(\phi \) and \(\phi '\) is then broken, leading to two different kinds of resonances, classically referred to as corotation eccentric resonance (CER) and Lindblad eccentric Resonance (LER), respectively. We write the four reduced equations of motion near the CER and LER, that form what we call the CoraLin model. This model depends upon only two dimensionless parameters that control the dynamics of the system: the distance \(D\) between the CER and LER, and a forcing parameter \(\epsilon _L\) that includes both the mass and the orbital eccentricity of the disturbing satellite. Three regimes are found: for \(D=0\) the system is integrable, for \(D\) of order unity, it exhibits prominent chaotic regions, while for \(D\) large compared to 2, the behavior of the system is regular and can be qualitatively described using simple adiabatic invariant arguments. We apply this model to three recently discovered small Saturnian satellites dynamically linked to Mimas through first order mean motion resonances: Aegaeon, Methone and Anthe. Poincaré surfaces of section reveal the dynamical structure of each orbit, and their proximity to chaotic regions. This work may be useful to explore various scenarii of resonant capture for those satellites.

Polarization properties of solid-state organic lasers

The polarization states of lasers are crucial issues both for practical applications and fundamental research. In general, they depend in a combined manner on the properties of the gain material and on the structure of the electromagnetic modes. In this paper, we address this issue in the case of solid-state organic lasers, a technology which enables one to vary independently gain and mode properties. Different kinds of resonators are investigated: in-plane microresonators with Fabry-Perot, square, pentagon, stadium, disk, and kite shapes, and external vertical resonators. The degree of polarization $P$ is measured in each case. It is shown that although transverse electric modes prevail generally ($P$ > 0), the kite-shaped microlaser generates negative values for $P$ (i.e., a flip of the dominant polarization which becomes mostly transverse magnetic polarized). In general, we demonstrate that both the pump polarization and the resonator geometry can be used to tailor the polarization of organic lasers. With this aim in view, we, at last, investigate two other degrees of freedom, namely upon using resonant energy transfer and upon pumping the laser dye to a higher excited state. We then demonstrate that significantly lower $P$ factors can be obtained.

Numerical simulation of finite amplitude standing waves in acoustic resonators using finite volume method

Finite amplitude standing waves in acoustic resonators are simulated. The fluid is initially at rest and excited by a harmonic motion of the entire resonator. The unsteady compressible Navier–Stokes equations and the state equation for an ideal gas are employed. This study extends the traditional pressure based finite volume SIMPLEC scheme for solving the equations without any predefined standing waves. The pressure waveforms are computed in three different closed resonators and two opened resonators. The studied shapes of resonators include cylinder, cone and exponential horn. The numerical results obtained from the proposed finite volume method in the study are in agreement with those obtained with the Galerkin method and the finite difference method. We also investigate the velocity waveforms in the three different kinds of resonators, and finds that the sharp velocity spikes appear at the ends of the resonator when the pressure has a shock-like waveform. The velocity in the closed conical resonator displays a smooth harmonic waveform. Finally, the pressure waveforms in opened resonators are simulated and analyzed. The results show that the decrease in the ratio of the maximum to the minimum pressure at the small end of the exponential resonator is less than that of cylindrical resonators when the flow velocity at the opened end (relative to the resonator) is the same.

Near-field investigations of nanoshell cylinder dimers

Metallic nanoparticles are known to exhibit strong particle size dependent localized surface plasmon resonances due to their specific optical response described via the complex dielectric function. Using the two-dimensional finite element method, the near-field behavior of core-shell nanocylinder dimers with either a dielectric or a gold core and a silver shell was investigated. With a detailed analysis the positions of maximum field enhancement usable for highly sensitive spectroscopy were unveiled and the surface charge distributions of the different kinds of resonances were visualized. It is shown that the usual far-field spectra do not give reliable estimates of local electric field peaks. Furthermore one observes a distinct mode at the natural plasma frequency of the silver shell which is independent of the core material. This mode is identified as a volume plasmon mode.

Carrier-carrier entanglement and transport resonances in semiconductor quantum dots

We study theoretically the entanglement created in a scattering between an electron, incoming from a source lead, and another electron bound in the ground state of a quantum dot, connected to two leads. We analyze the role played by the different kinds of resonances in the transmission spectra and by the number of scattering channels, into the amount of quantum correlations between the two identical carriers. It is shown that the entanglement between their energy states is not sensitive to the presence of Breit-Wigner resonances, while it presents a peculiar behavior in correspondence to Fano peaks: two close maxima separated by a minimum for a two-channel scattering and a single maximum for a multichannel scattering. Such a behavior is ascribed to the different mechanisms characterizing the two types of resonances. Our results suggest that the production and detection of entanglement in quantum dot structures may be controlled by the manipulation of Fano resonances through external fields.

Transmission properties of two shifted magnetoinductive waveguides

AbstractTransmission properties of magnetoinductive waves propagating in two coupled one‐dimensional metamaterial arrays are studied both experimentally and theoretically for the case when one of the arrays is shifted relative to the other one. Two different kinds of resonant metamaterial elements, split‐pipe and spiral resonators, are investigated in the frequency bands centred at 46.2 and 586 MHz, respectively. It is shown that within a certain frequency range close to the resonant frequencies the transmission is strongly dependent on the shift. Theoretical calculations based on the impedance matrix show good agreement with the experimental results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1054–1058, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22344

Stability of photovoltaic and wind turbine grid-connected inverters for a large set of grid impedance values

The aim of this paper is to analyze the stability problems of grid connected inverters used in distributed generation. Complex controllers (e.g., multiple rotating dq-frames or resonant-based) are often required to compensate low frequency grid voltage background distortion and an LCL-filter is usually adopted for the high frequency one. The possible wide range of grid impedance values (distributed generation is suited for remote areas with radial distribution plants) challenge the stability and the effectiveness of the LCL-filter-based current controlled system. It has been found out and it will be demonstrated in this paper that the use of active damping helps to stabilise the system in respect to many different kinds of resonances. The use of active damping results in an easy plug-in feature of the generation system in a vast range of grid conditions and in a more flexible operation of the overall system able to manage sudden grid changes. In the paper, a vast measurement campaign made on a single-phase system and on a three-phase system used as scale prototypes for photovoltaic and wind turbines, respectively, validate the analysis.

Dynamical chiral bag model

We study a dynamical chiral bag model, in which massless fermions are confined within an impenetrable but movable bag coupled to meson fields. The self-consistent motion of the bag is obtained by solving the equations of motion exactly assuming spherical symmetry. When the bag interacts with an external meson wave we find three different kinds of resonances: {\it fermionic}, {\it geometric}, and $\sigma$-resonances. We discuss the phenomenological implications of our results.