Resonance Splitting Research Articles

Electromagnetically induced transparency metamaterial with strong toroidal dipole response

This paper designs a planar electromagnetically induced transparency (EIT) metamaterial, which comprises an asymmetric ellipse split resonance ring (AESRR) and cut wire (CW). The proposed EIT metamaterial works in the wide range of incident angles and has polarization-sensitive at two transmission dips. The frequency of transparency peak is 10.67 GHz and maintains a high quality-factor (180.84). By calculating the multipole’s radiated power, it can be found that the toroidal dipole response is enhanced, while the electric dipole response is suppressed at the transparency peak. Interestingly, this paper firstly uses the radiated power of electric dipole to elucidate the polarization sensitivity in two minimal transmissions. Meanwhile, the coupling mechanism of the EIT metamaterial is analyzed by the two-oscillator model and equivalent circuit.

Abstract OT3-02-01: Accuracy of split dynamic magnetic resonance imaging in locally advanced breast cancer during neoadjuvant aromatase inhibitor therapy

Abstract Background: Neoadjuvant aromatase inhibitor (AI) therapy is an efficient treatment option in highly selected postmenopausal patients with strongly hormone receptor positive locally advanced breast cancer (LABC) to obtain a tumor downstaging prior to breast surgery with acceptable response rates when standard chemotherapy is not indicated. The tumor response evaluation during therapy is of crucial importance but often-suboptimal using standard procedures. Contrast enhanced magnetic resonance imaging (MRI) is currently the most sensitive of the available imaging modalities in detection and characterization of a breast tumor before and during neoadjuvant therapy. The sub-study presented here was designed to test a novel technique called split dynamic MRI in which a high temporal resolution multi-echo sequence is interleaved with a standard dynamic high spatial resolution sequence during a single bolus injection. This method has an advantage over the current dynamic MRI, as it provides extensive information about both structural and functional assessment of the tumor through quantitative evaluation of both T1- and T2 *- weighted characteristics. Trial Design: NEO-LET-EXE is a neoadjuvant, randomized, open-label, intra-patient cross-over trial. Eligibility criteria: Postmenopausal patients diagnosed with estrogen receptor (ER) positive (≥10%) breast cancer and HER-2 negative LABC not suitable for neoadjuvant chemotherapy are eligible for the study. Specific aims: A 1.5T scanner is used to obtain and investigate the clinical utility and diagnostic accuracy of T1_T2 multi-echo EPI and dynamic THRIVE sequences during a single injection of contrast agent at baseline and following AI therapy with either letrozole or exemestane for at least two months followed by the alternative drug for another two months. The study clarifies the feasibility of split dynamic MRI method as a tool for predict treatment response, analyse biological behaviour and tumor aggressiveness. In addition, our findings will allow quantitative comparisons of the intra-tumor effects of aromatase inhibitors with clinical breast evaluations for prediction of postoperative pathologic complete response. Statistical methods: Quantitative analysis will be performed with pharmacokinetic modelling on T1-weighted images and estimation of maximum peak change in R2* images using receiver operating characteristic (ROC) analysis. Two radiologists are interpreting high spatial resolution data. Mann-Whitney tests will be used to determine the parameters ability for establishing and characterization of the tumor. Present accrual and target accrual: The study has currently enrolled 55 patients (of planned 100) at the Akershus University Hospital, Norway. Accrual is planned to be completed within the next 2 years. Our early experience with the applied technology will be presented and discussed. Citation Format: Joana Reis. Accuracy of split dynamic magnetic resonance imaging in locally advanced breast cancer during neoadjuvant aromatase inhibitor therapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT3-02-01.

Influence of Coupling Strength Between a Magnetic Quantum Dot and Quantum Hall Edge Channels on Valley-isospin-dependent Dirac Fermion Transport

We investigate Dirac fermion transport through opposite quantum Hall edge channels in armchair graphene nanoribbons where a magnetic quantum dot (MQD) is placed between the edges. The resulting conductance shows distinguished resonant features according to the angle Φ between the valley isospins at the opposite edges. Particularly, for Φ = 0, the conductance exhibits a behavior characteristic of dissipative resonances when the edge—dot distance is sufficiently small even though the unitarity of the whole system is conserved. As the edge—dot distance increases, a crossover behavior emerges between two distinct regimes: largely perturbed and unperturbed MQD. Resonant energy converges to a specific energy corresponding to the eigenenergy of the localized states in the unperturbed MQD. For sufficiently weak couplings, a fine splitting of the conductance resonances is observed, of which splitting energy is several μeV. The finding of these finely split localized states in the MQD allows us to better elucidate related electronic and transport properties in graphene.

Tunable electromagnetically induced transparency based on graphene metamaterials

In this paper we propose a graphene-based metasurface structure that can exhibit tunable electromagnetically-induced-transparency-like (EIT) spectral response at mid-infrared frequencies. The metasurface structure is composed of two subwavelength mono-layer graphene nano-disks coupled with a mono-layer graphene nano-strip. We show that the coupling of the nano-disks' dipole resonance with the quadrupole resonance of the nano-strip can create two split resonances with a transparency window in between at any desired center frequency within a wide frequency range. We show that such an EIT-like response can also be dynamically shifted in frequency by adjusting the Fermi-level of the graphene through external voltage control, which provides convenient post-fabrication tunability. In addition, the performance of such a metastructure for sensing the refractive index of the surrounding medium is analyzed. The simulation results show that its sensitivity can reach 3016.7 nm/(RIU) with a FOM exceeding 12.0. Lastly, we present an analysis of the slow light characteristics of the proposed device, where the group index can reach as large as 200. Our design provides a new miniaturized sensing platform that can facilitate the development of biochemical molecules testing, etc.

Peculiarities of resonant interaction in paired impurity centers of 2-fluoronaphthalene in naphthalene

Fluorescence and absorption spectra of the 2-fluoronaphthalene admixtures in naphthalene were studied at low temperature (T = 4.2 К). Two types of pairwise impurity centers were formed at admixture concentrations of more than 1 wt%. Polarization of absorption bands was detected; these spectra were determined by resonance interactions between molecules of the impurity center. Resonant splitting of electronic levels for the translationally nonequivalent molecules in the unit cell of the naphthalene crystal was analyzed for the case, when one molecule was in the similar phase with the incident light wave and the other one was in antiphase.

Modulational instability and frequency combs in whispering-gallery-mode microresonators with backscattering

We introduce the first principle model describing frequency comb generation in a WGM microresonator with the backscattering-induced coupling between the counter-propagating waves. {Elaborated model provides deep insight and accurate description of the complex dynamics of nonlinear processes in such systems.} We analyse the backscattering impact on the splitting and reshaping of the nonlinear resonances, demonstrate backscattering-induced modulational instability in the normal dispersion regime and subsequent frequency comb generation. We present and discuss novel features of the soliton comb dynamics induced by the backward wave.

Reconfigurable Frequency-Selective Resonance Splitting in Chalcogenide Microring Resonators

This paper reports a method to enable, for the first time, reconfigurable control of resonance splitting of one or multiple arbitrarily selected azimuthal orders in a microring resonator. This is a...

Single-site binding of pyrene to poly(ester-imide)s incorporating long spacer-units: prediction of NMR resonance-patterns from a fractal model.

Co-polycondensation of the diimide-based diols N,N′-bis(2-hydroxyethyl)hexafluoroisopropylidene-diphthalimide, (HFDI), and N,N′-bis(2-hydroxy-ethyl)naphthalene-1,4,5,8-tetracarboxylic-diimide, (NDI), with aliphatic diacyl chlorides ClOC(CH2)xCOCl (x = 5 to 8) affords linear copoly(ester-imide)s. Such copolymers interact with pyrene via supramolecular binding of the polycyclic aromatic at NDI residues. This interaction results in upfield complexation shifts and sequence-related splittings of the NDI 1H NMR resonances, but gives a very different final resonance-pattern from the copolymer where x = 2. Computational modelling of the polymer with x = 5 suggests that each pyrene molecule binds to just a single NDI residue rather than by intercalation between a pair of NDI's at a tight chain-fold, as was found for x = 2. The new single-site binding model enables the pattern of 1H NMR resonances for copolymers with longer spacers (x = 5 to 8) to be reproduced and assigned by simulation from sequence-specific shielding factors based on a type of fractal known as the last-fraction Cantor set. As this type of fractal also enables an understanding of pairwise binding systems, it evidently provides a general numerical framework for supramolecular sequence-analysis in binary copolymers.

Electronic and thermoelectric properties of a single pyrene molecule

We propose a system containing a single pyrene molecule sandwiched between two metallic electrodes. The transport properties of the single pyrene molecule with four configurations are investigated using a steady-state theoretical model. We calculate the transmission probability and the electric current for the structure (1, 8), the structure (1, 7), the structure (1, 5) and the structure (1, 4). By applying a gate voltage on the pyrene molecule, we calculate the thermoelectric properties. The thermoelectric and electron transport properties can be controlled by quantum interference, the contact geometry and the gate voltage. The asymmetric behavior and the splitting of resonances in the transmission spectrum occur due to applying a gate voltage on the pyrene molecule. As a result, the structures (1, 5) and (1, 7) have a maximum value of the figure of merit reaching to 0.8 at the Fermi level. According to the results, the structures (1, 5) and (1, 7) can be act as promising thermoelectric applications in molecular electronics.

Non-Hermitian ringlaser gyroscopes with enhanced Sagnac sensitivity.

Gyroscopes are essential to many diverse applications associated with navigation, positioning and inertial sensing1. In general, most optical gyroscopes rely on the Sagnac effect-a relativistically induced phase shift that scales linearly with the rotational velocity2,3. In ringlaser gyroscopes (RLGs), this shift manifests as a resonance splitting in the emission spectrum, which can be detected as a beat frequency4. The need for ever more precise RLGs has fuelled research activities aimed at boosting the sensitivity of RLGs beyond the limits dictated by geometrical constraints, including attempts to use either dispersive or nonlinear effects5-8. Here we establish and experimentally demonstrate a method using non-Hermitian singularities, or exceptional points, to enhance the Sagnac scale factor9-13. By exploiting the increased rotational sensitivity of RLGs in the vicinity of an exceptional point, we enhance the resonance splitting by up to a factor of 20. Our results pave the way towards the next generation of ultrasensitive and compact RLGs and provide a practical approach for the development of other classes of integrated sensor.

Polarization property of light scattered on dielectric nanorods at oblique incident angle

We report the study of light polarization property upon scattering off a dielectric nanorod in which the direction of the incident light is at an angle with respect to the cylinder main axis. The numerical work is done on the basis of the cylindrical Mie theory. It is shown that for incident light with different polarization, the resulted scattering cross-section spectra will also show different characteristics with varying incident angles. For TE case, resonance splitting is observed due to excitation of a new resonance mode, while for TM case, resonance merging is observed. An interference effect between different resonance modes due to variation of incident angle is then resulted in suppression of backward scattering intensity for TM case. Meanwhile, for TE case, at illumination angle approaching grazing angle, a spectral range exists whereby the scattered wave’s angular intensity profile forms a perpendicular dipolar feature with different polarization. The reported results may be useful for aplication of nanoantenna, photovoltaic, and polarization conversion.

Enhanced Sensing and Nondegraded Thermal Noise Performance Based on PT-Symmetric Electronic Circuits with a Sixth-Order Exceptional Point.

An exceptional point (EP) is a non-Hermitian degeneracy where both eigenvalues and their corresponding eigenvectors coalesce. It was recently proposed and demonstrated that such spectral singularity can be utilized for enhanced sensing. Potential drawbacks of EP sensing include both fundamental resolution limit and noise effects that might mask the hypersensitive resonant splitting. Here, we address these issues by proposing a parity-time (PT)-symmetric sensing circuit bearing a sixth-order EP. By employing capacitive coupling channel as a sensing platform, we achieve an enhanced resonance shift proportional to the fourth-order root of the perturbation strength and maintain a high resolution for weak perturbation. Due to the low-pass feature of our circuit, thermal noise is mitigated down to a level comparable to its Hermitian counterpart, despite the presence of highly noisy gain and loss elements. Our EP sensing scheme offers combined enhanced sensitivity, improved resolution and nondegraded thermal noise performance, showing an exciting prospect for next-generation sensing technologies.

Portable microresonator-based label-free detector: monotonous resonance splitting with particle adsorption.

Whispering gallery mode resonators hold great promises as very sensitive detectors, with a wide range of applications, notably as biosensors. However, in order to monitor the fine variations in their resonances, a costly and bulky apparatus is required, which confines the use of these efficient tools within specialised labs. Here, we consider a micro-ring resonator that is completely covered by a Bragg grating and propose to functionalize it only over a quarter of its perimeter. As target molecules progressively bind to the active region of the resonator, some particular resonances near the edge of the band gap undergo monotonous frequency splitting. Such a splitting, within the GHz range, can be monitored by conventional electronics and, hence, does not require finely tunable lasers or spectrometers. Meanwhile, the ultrahigh sensitivity that is characteristic of whispering gallery mode resonators is maintained. This robust and sensitive self-heterodyne detection scheme may pave the way to portable whispering-gallery-mode-based detectors, and in particular to point-of-care diagnostic tools.

Improved HNA isotropic etching for large-scale highly symmetric toroidal silicon molds with <10-nm roughness

Microsystem technology is well suited to batch fabricate microhemispherical resonator gyroscopes (HRG) to reduce cost and volume. In the processing of micro-HRG, a crucial step is to get a 3-D hemispherical mold with the large-scale, high-symmetry, and smooth surface. Compared with the hemispherical resonator, the toroidal resonator has the smaller frequency split and larger effective resonance mass under the same processing accuracy. A wafer-scale etching method for the toroidal resonator mold was presented, which is based on the deep reactive ion etching and improved HNA isotropic etching. The advantages of this method include low cost, time savings, and easy operation. With this method, toroidal molds with an average diameter over 1900 μm, asymmetry

Determinants of Active-Site Inhibitor Interaction with HIV-1 RNase H.

The ribonuclease H (RNH) activity of HIV-1 reverse transcriptase (RT) is essential for viral replication and can be a target for drug development. Yet, no RNH inhibitor to date has substantial antiviral activity to allow advancement into clinical development. Herein, we describe our characterization of the detailed binding mechanisms of RNH active-site inhibitors, YLC2-155 and ZW566, that bind to the RNH domain through divalent metal ions, using NMR, molecular docking, and quantum mechanical calculations. In the presence of Mg2+, NMR spectra of RNH exhibited split (two) resonances for some residues upon inhibitor binding, suggesting two binding modes, an observation consistent with the docking results. The relative populations of the two binding conformers were independent of inhibitor or Mg2+ concentration, with one conformation consistently more favored. In our docking study, one distinctive pose of ZW566 showed more interactions with surrounding residues of RNH compared to the analogous binding pose of YLC2-155. Inhibitor titration experiments revealed a lower dissociation constant for ZW566 compared to YLC2-155, in agreement with its higher inhibitory activity. Mg2+ titration data also indicated a stronger dependence on Mg2+ for the RNH interaction with ZW566 compared to YLC2-155. Combined docking and quantum mechanical calculation results suggest that stronger metal coordination as well as more protein-inhibitor interactions may account for the higher binding affinity of ZW566. These findings support the idea that strategies for the development of potent competitive active site RNH inhibitors should take into account not only metal-inhibitor coordination but also protein-inhibitor interaction and conformational selectivity.

Magnetic-field-induced splitting and polarization of monolayer-based valley exciton polaritons

Atomically thin crystals of transition metal dichalcogenides are ideally suited to study the interplay of light-matter coupling, polarization and magnetic field effects. In this work, we investiagte the formation of exciton-polaritons in a MoSe2 monolayer, which is integrated in a fully-grown, monolithic microcavity. Due to the narrow linewidth of the polaritonic resonances, we are able to directly investigate the emerging valley Zeeman splitting of the hybrid light-matter resonances in the presence of a magnetic field. At a detuning of -54.5 meV (13.5 % matter constituent of the lower polariton branch), we find a Zeeman splitting of the lower polariton branch of 0.36 meV, which can be directly associated with an excitonic g factor of 3.94\pm0.13. Remarkably, we find that a magnetic field of 6T is sufficient to induce a notable valley polarization of 15 % in our polariton system, which approaches 30% at 9T. Strikingly, this circular polarization degree of the polariton (ground) state exceeds the polarization of the exciton reservoir for equal magnetic field magnitudes by approximately 50%, as a consequence of enhanced relaxation of bosons in our monolayer-based system.

Design and Realization of a Coreless and Magnetless Electric Motor Using Magnetic Resonant Coupling Technology

Electric motors have a wide range of applications in a diverse range of industries. This paper presents a novel magnetic resonant coupling motor (MRCM), constructed without any iron or permanent-magnet core, i.e., a novel coreless and magnetless electric motor. Different from the conventional operation principle of existing electric motors, the application of the wireless power transfer system using magnetic resonant coupling technology is the key feature of the proposed MRCM. By adjusting the excitation frequency in accordance with the trajectory of resonant frequency splitting, a large electromagnetic force in different direction can be developed. Besides, the proposed MRCM has an inherent merit of unity power factor. This paper presents a new design concept, which could well be a promising start for a new generation of future electric motor.

High-sensitivity real-splitting anti-PT-symmetric microscale optical gyroscope.

Optical gyroscopes measure the angular velocity using the Sagnac effect. However, the resonance splitting due to the Sagnac effect is directly proportional to the linear dimensions of the device. Consequently, integrated optical gyroscopes are still the subject of research. We propose the idea and the design of an anti-parity-time (APT)-symmetric optical gyroscope exhibiting a resonance splitting independent from the dimensions of the device. With a 80 μm×40 μm footprint integrated device, we demonstrated that it is possible to achieve a resonance splitting 106 times higher than the one obtained through the classical Sagnac effect. With respect to the previously proposed parity-time (PT)-symmetric gyroscope, our solution exhibits a real frequency splitting, directly measurable at the output power spectrum. Moreover, it can be kept at its exceptional point more accurately than the PT-symmetric counterpart. Finally, the anti-PT-symmetric gyroscope presented here can detect the sign of the angular velocity differently from the PT-symmetric one.

Resonant peak splitting in finite periodic superlattices with an unit cell of two barriers and two wells on monolayer graphene

The general expressions for transmission probability and resonant peaks in one-dimensional N-periods graphene superlattice with unit cell of two barriers and two wells are analytically derived, and two types of resonant peaks are obtained: (1) the periodicity induced resonant peaks splitting of (N − 1)-fold as N increases; and (2) the resonant peak through a unit cell unchanged as N varies. As the two-barriers in unit cell become asymmetric, the resonance transmission probability of unit cell becomes imperfect (T1 < 1), which drops quickly with the unit asymmetry increases. Thus, the unit cell related resonant peak could only be observed in superlattices with less unit cell asymmetry of a few of period numbers. With the period increases, the unit related resonant peak disappears and only periodicity induced (N − 1)-fold splitting remains. The splitting rule is further confirmed by the conductance and noise versus the incident energy and the misunderstandings in publication domain is cleared up.

Hermitian and Non-Hermitian Mode Coupling in a Microdisk Resonator Due to Stochastic Surface Roughness Scattering

We make use of a phase-sensitive set-up to study the light transmission through a coupled waveguide-microdisk system. We observe a splitting of the transmission resonance leading to an unbalanced doublet of dips. The experimental data are analyzed by using a phasor diagram that correlates the real and the imaginary parts of the complex transmission. In addition, detailed features are evidenced by a complex inverse representation of the data that maps ideal resonances into straight lines and split resonances into complicated curves. Modeling with finite element method simulations suggests that the splitting and the unbalance is caused by an induced chirality in the propagation of the optical fields in the microdisk due to the interplay between the stochastic roughness and the intermodal dissipative coupling, which yield an asymmetric behavior. An analytical model based on the temporal coupled mode theory shows that both a reactive and a dissipative coupling of the counter-propagating modes by the surface roughness of the ring resonator are required to quantitatively reproduce the experimental observations and the numerical simulations.