Comparisons between the 35 mm Quadrature Surface Resonator at 300 K and the 40 mm High-Temperature Superconducting Surface Resonator at 77 K in a 3T MRI Imager

This study attempts to compare the signal-to-noise ratio (SNR) of the 40 mm High-Temperature Superconducting (HTS) surface resonator at 77 K and the 35 mm commercial quadrature (QD) surface resonator at 300 K in a 3 Tesla (T) MRI imager. To aquire images for the comparison, we implemented a phantom experiment using the 40 mm diameter Bi₂Sr₂Ca₂Cu₃O_x (Bi-2223) HTS surface resonator, the 35 mm commercial QD surface resonator and the 40 mm professionally-made copper surface resonator. The HTS surface resonator at 77 K provided a 1.43-fold SNR gain over the QD surface resonator at 300 K and provided a 3.84-fold SNR gain over the professionally-made copper surface resonator at 300 K on phantom images. The results agree with the predictions, and the difference between the predicted SNR gains and measured SNR gains is 1%. Although the geometry of the HTS surface resonator is different from the QD surface resonator, its SNR is still higher. The results demonstrate that a higher image quality can be obtained with the HTS surface resonator at 77 K. With the HTS surface resonator, the SNR can be improved, suggesting that the HTS surface resonator is a potentially helpful diagnostic tool for MRI imaging in various applications.     

Whole body screening using high-temperature superconducting MR volume resonators: mice studies

High temperature superconducting (HTS) surface resonators have been used as a low loss RF receiver resonator for improving magnetic resonance imaging image quality. However, the application of HTS surface resonators is significantly limited by their filling factor. To maximize the filling factor, it is desirable to have the RF resonator wrapped around the sample so that more nuclear magnetic dipoles can contribute to the signal. In this study, a whole new Bi(2)Sr(2)Ca(2)Cu(2)O(3) (Bi-2223) superconducting saddle resonator (width of 5 cm and length of 8 cm) was designed for the magnetic resonance image of a mouse's whole body in Bruker 3 T MRI system. The experiment was conducted with a professionally-made copper saddle resonator and a Bi-2223 saddle resonator to show the difference. Signal-to-noise ratio (SNR) with the HTS saddle resonator at 77 K was 2.1 and 2 folds higher than that of the copper saddle resonator at 300 K for a phantom and an in-vivo mice whole body imaging. Testing results were in accordance with predicted ones, and the difference between the predicted SNR gains and measured SNR gains were 2.4%～2.7%. In summary, with this HTS saddle system, a mouse's whole body can be imaged in one scan and could reach a high SNR due to a 2 folds SNR gain over the professionally-made prototype of copper saddle resonator at 300 K. The use of HTS saddle resonator not only improves SNR but also enables a mouse's whole body screen in one scan.     

A thin film electro-acoustic enzyme biosensor allowing the detection of trace organophosphorus pesticides

We report an analytical method using a thin film electro-acoustic resonator for the detection of organophosphorus pesticides. The acetylcholinesterase (AChE) enzyme was immobilized on the surface of the resonator. In the presence of organophosphorus compounds, the degree of inhibitory effect of organophosphorus compounds on the AChE activity and the concentration of pesticides were detected in real time by measuring the frequency shift of the resonator. The proposed device has a remarkably low detection limit of 1.8×10(-11)M and obvious advantages such as small size, simple operation, and integrated circuit compatibility, providing a promising tool for pesticide analysis.     

Electrochemically induced disintegration of layer-by-layer-assembled thin films composed of 2-iminobiotin-labeled poly(ethyleneimine) and avidin

A layer-by-layer assembly composed of avidin and 2-iminobiotin-labeled poly(ethyleneimine) (ib-PEI) was prepared on the surface of a platinum (Pt) film-coated quartz resonator, and an electrochemically induced disintegration of the avidin-ib-PEI assembly was studied using a quartz crystal microbalance. The resonance frequency of a five-bilayer (avidin-ib-PEI)5 film-coated quartz resonator was increased upon application of an electric potential to the Pt layer of the quartz resonator, suggesting that the mass on the quartz resonator was decreased as a result of disintegration of the (avidin-ib-PEI)5 film, due to a pH change in the vicinity of the surface of the Pt-coated quartz resonator. It may be that the (avidin-ib-PEI)5 film assembly was decomposed by acidification of the local pH on the surface of the Pt layer, which in turn was induced through electrolysis of water on Pt, because ib-PEI forms complexes with avidin only in basic media. In pH 9 solution, the (avidin-ib-PEI)5 film was decomposed under the influence of an applied potential of 0.6-1.0 V versus Ag/AgCl. The (avidin-ib-PEI)5 film was decomposed almost completely within a minute in a low concentration buffer (1 mM, pH 9), while the decomposition was slower in 10 and 100 mM buffer solutions at the same pH. The decomposition of the assembly was rapid when the electrode potential was applied in pH 9 solutions, while the response was relatively slow in pH 10 and 11 solutions. All the results are rationalized on the basis of an electrochemically induced acidification of the local environment around the (avidin-ib-PEI)5 film on the Pt layer.     

Response Line-Shapes in Compact Coupled Plasmonic Resonator Systems

A compact plasmonic coupled-resonator system, consisting of a stub resonator and baffles in the metal–insulator–metal waveguide, is numerically investigated with the finite element method. Simulations show that sharp and asymmetric response line-shapes can occur in the system. The asymmetric line-shapes in the transmission spectra depend on the relative positions of the resonant wavelengths between the single-stub resonator and the inner resonator constructed by the baffle and the stub resonator, while the other part of the transmission spectra (except the asymmetric part) maintains the spectral features of the structure constructed by the baffles. An analytic model and a relative phase analysis based on the scattering matrix theory are used to describe and explain this phenomenon. These sharp and asymmetric response line-shapes are important for improving the nano-plasmonic devices’ performances.     

Beamline characterization of a dielectric-filled reentrant cavity resonator as beam current monitor for a medical cyclotron facility

At PSI (Paul Scherrer Institute), Switzerland, a superconducting cyclotron called “COMET” delivers proton beam of 250 MeV pulsed at 72.85 MHz for proton radiation therapy. Measuring proton beam currents (0.1–10nA) is of crucial importance for the treatment safety and is usually performed with invasive monitors such as ionisation chambers (ICs) which degrade the beam quality. A new non-invasive beam current monitor working on the principle of electromagnetic resonance is built to replace ICs in order to preserve the beam quality delivered. The fundamental resonance frequency of the resonator is tuned to 145.7 MHz, which is the second harmonic of the pulse rate, so it provides signals proportional to beam current. The cavity resonator installed in the beamline of the COMET is designed to measure beam currents for the energy range 238–70 MeV. Good agreement is reached between expected and measured resonator response over the energy range of interest. The resonator can deliver beam current information down to 0.15 nA for a measurement integration time of 1 s. The cavity resonator might be applied serving as a safety monitor to trigger interlocks within the existing domain of proton radiation therapy. Low beam currents limit the abilities to detect sufficiently, however, with the potential implementation of FLASH proton therapy, the application of cavity resonator as an online beam-monitoring device is feasible.     

Utilizing the Metallic Nano-Rods in Hexagonal Configuration to Enhance Sensitivity of the Plasmonic Racetrack Resonator in Sensing Application

A high sensitive plasmonic refractive index sensor based on metal-insulator-metal (MIM) waveguides with embedding metallic nano-rods in racetrack resonator has been proposed. The refractive index changes of the dielectric material inside the resonator together with temperature changes can be acquired from the detection of the resonance wavelength, based on their linear relationship. With optimum design and considering a tradeoff among detected power, structure size, and sensitivity, the finite difference time domain simulations show that the refractive index and temperature sensitivity values can be obtained as high as 2610 nm per refractive index unit (RIU) and 1.03 nm/°C, respectively. In addition, resonance wavelengths of resonator are obtained experimentally by using the resonant conditions. The effects of nano-rods radius and refractive index of racetrack resonator are studied on the sensing spectra, as well. The proposed structure with such high sensitivity will be useful in optical communications that can provide a new possibility for designing compact and high-performance plasmonic devices.     

Inverse Design of Dielectric Resonator Cloaking Based on Topology Optimization

In many applications, a cloaked resonator is highly desired, which can harvest and maximize the energy within the resonator without being detected. This paper presents the resonator cloaking achieved by topology optimization-based inverse design methodology. The resonator cloaking is inversely designed by solving the topology optimization problem with minimizing the ratio of the scattering field energy outside the cloak and the cloaked resonating field energy. By inversely designing the resonator cloaking with relative permittivity 2 for both the resonator and cloak, the topology optimization-based inverse design methodology is demonstrated, where the incident angle sensitivity is considered to derive incident angle insensitive design. Then, the proposed methodology is applied for the cases with resonator and cloak materials chosen from dielectrics with low, moderate and high permittivity, respectively. The derived results demonstrate that the resonator cloaking can be categorized into three types, which are the Fabry-Pérot resonance cloaking, Mie resonance cloaking and hybrid resonance cloaking.     

Planar Quadrature RF Transceiver Design Using Common-Mode Differential-Mode (CMDM) Transmission Line Method for 7T MR Imaging

The use of quadrature RF magnetic fields has been demonstrated to be an efficient method to reduce transmit power and to increase the signal-to-noise (SNR) in magnetic resonance (MR) imaging. The goal of this project was to develop a new method using the common-mode and differential-mode (CMDM) technique for compact, planar, distributed-element quadrature transmit/receive resonators for MR signal excitation and detection and to investigate its performance for MR imaging, particularly, at ultrahigh magnetic fields. A prototype resonator based on CMDM method implemented by using microstrip transmission line was designed and fabricated for 7T imaging. Both the common mode (CM) and the differential mode (DM) of the resonator were tuned and matched at 298MHz independently. Numerical electromagnetic simulation was performed to verify the orthogonal B₁ field direction of the two modes of the CMDM resonator. Both workbench tests and MR imaging experiments were carried out to evaluate the performance. The intrinsic decoupling between the two modes of the CMDM resonator was demonstrated by the bench test, showing a better than -36 dB transmission coefficient between the two modes at resonance frequency. The MR images acquired by using each mode and the images combined in quadrature showed that the CM and DM of the proposed resonator provided similar B₁ coverage and achieved SNR improvement in the entire region of interest. The simulation and experimental results demonstrate that the proposed CMDM method with distributed-element transmission line technique is a feasible and efficient technique for planar quadrature RF coil design at ultrahigh fields, providing intrinsic decoupling between two quadrature channels and high frequency capability. Due to its simple and compact geometry and easy implementation of decoupling methods, the CMDM quadrature resonator can possibly be a good candidate for design blocks in multichannel RF coil arrays.     

Tunable Multimode Plasmonic Filter Based on Side-Coupled Ring-Groove Joint Resonator

Plasmonics - A tunable multimode plasmonic filter is proposed by using a side-coupled ring-groove joint resonator. In addition to the integer resonance modes of the perfect ring resonator (RR),...     

Electrodynamic eigenmodes in cellular morphology

Eigenmodes of the spherical and ellipsoidal dielectric electromagnetic resonator have been analysed. The sizes and shape of the resonators have been chosen to represent the shape of the interphase and dividing animal cell. Electromagnetic modes that have shape exactly suitable for positioning of the sufficiently large organelles in cell (centrosome, nucleus) have been identified. We analysed direction and magnitude of dielectrophoretic force exerted on large organelles by electric field of the modes. We found that the TM(1m1) mode in spherical resonator acts by centripetal force which drags the large organelles which have higher permittivity than the cytosol to the center of the cell. TM-kind of mode in the ellipsoidal resonator acts by force on large polarizable organelles in a direction that corresponds to the movement of the centrosomes (also nucleus) observed during the cell division, i.e. to the foci of the ellipsoidal cell. Minimal required force (10(-16)N), gradient of squared electric field and corresponding energy (10(-16)J) of the mode have been calculated to have biological significance within the periods on the order of time required for cell division. Minimal required energy of the mode, in order to have biological significance, can be lower in the case of resonance of organelle with the field of the cellular resonator mode. In case of sufficient energy in the biologically relevant mode, electromagnetic field of the mode will act as a positioning or steering mechanism for centrosome and nucleus in the cell, thus contribute to the spatial and dynamical self-organization in biological systems.     

On-Chip THz Detection of Biomaterials: A Numerical Study

The marker-free on-chip distinction betweenhybridised (double-stranded) DNA (HDNA) anddenatured (single-stranded) DNA (DDNA) hasrecently been demonstrated using ultrashortelectrical pulses. The electrical THzpulses propagate in integrated waveguidesincorporating resonant THz structures ontowhich the genetic material is deposited.For a possible future realisation of a highthroughput array, it is crucial to optimizethe experimental parameters and theresonant structure. In this paper weperform a first numerical study ofdifferent resonator geometries and examinethe influence of critical experimentalparameters on the transmissioncharacteristics of the resonant structures.Our simulations demonstrate that the ringresonator shows a comparable performance tothe parallel-coupled resonator previouslyused in a first demonstration by Nagel andcoworkers.     

Electromagnetically Induced Transparency and Refractive Index Sensing for a Plasmonic Waveguide with a Stub Coupled Ring Resonator

A plasmonic refractive index sensor based on electromagnetically induced transparency (EIT) composed of a metal-insulator-metal (MIM) waveguide with stub resonators and a ring resonator is presented. The transmission properties and the refractive index sensitivity are numerically studied with the finite element method (FEM). The results revealed an EIT-like transmission spectrum with an asymmetric line profile and a refractive index sensitivity of 1057 nm/RIU are obtained. The coupled mode theory (CMT) based on transmission line theory is adopted to illustrate the EIT-like phenomenon. Multiple EIT-like peaks are observed in the transmission spectrum of the derived structures based on the MIM waveguide with stub resonator coupled ring resonator. To analyze the multiple EIT-like modes of the derived structures, the H _z field distribution is calculated. In addition, the effect of the structural parameters on the EIT-like effect is also studied. These results provide a new method for the dynamic control of light in the nanoscale.     

A Temperature-Stable Cryo-System for High-Temperature Superconducting MR In-Vivo Imaging

To perform a rat experiment using a high-temperature superconducting (HTS) surface resonator, a cryostat is essential to maintain the rat''s temperature. In this work, a compact temperature-stable HTS cryo-system, keeping animal rectal temperature at 37.4°C for more than 3 hours, was successfully developed. With this HTS cryo-system, a 40-mm-diameter Bi₂Sr₂Ca₂Cu₃O_x (Bi-2223) surface resonator at 77 K was demonstrated in a 3-Tesla MRI system. The proton resonant frequency (PRF) method was employed to monitor the rat''s temperature. Moreover, the capacity of MR thermometry in the HTS experiments was evaluated by correlating with data from independent fiber-optic sensor temperature measurements. The PRF thermal coefficient was derived as 0.03 rad/°C and the temperature-monitoring architecture can be implemented to upgrade the quality and safety in HTS experiments. The signal-to-noise ratio (SNR) of the HTS surface resonator at 77 K was higher than that of a professionally made copper surface resonator at 300 K, which has the same geometry, by a 3.79-fold SNR gain. Furthermore, the temperature-stable HTS cryo-system we developed can obtain stable SNR gain in every scan. A temperature-stable HTS cryo-system with an external air-blowing circulation system is demonstrated.     

Microring Switching Control Using Plasmonic Ring Resonator Circuits for Super-Channel Use

The multi-wavelength selection and switching system using the hybrid plasmonic add-drop ring resonator (HPARR) for optical communication is proposed for multi-carrier super-channel-based designed. The plasmonic polariton technique applied in the ring resonator mode to the alternate waveguide interferometer switches the multi-wavelength laser emission in the various ranges. The combination of curvature-coupled plasmon ring and substances with different refractive index allows switching the multi-wavelength emission to shorter the free spectrum range (FSR) and specific wavelengths, without an applied pump signal or adjusted the ring size. It is suitable for the super-channel of wavelength division multiplex (WDM) in the future optical network.

     

All-Optical Logic Gates Using a Plasmonic MIM Waveguide and Elliptical Ring Resonator

Plasmonics - All-optical logic gates OR, XOR, AND, and NOT based on two-dimensional (2D) plasmonic metal-insulator-metal (MIM) coupled with an elliptical ring resonator (ERR) are presented,...     

Applications of Tunable Mid-Infrared Plasmonic Square-Nanoring Resonator Based on Graphene Nanoribbon

Plasmonics - In this work, different structures are designed based on graphene square-nanoring resonator (GSNR) and simulated by the three-dimensional finite-difference time-domain (3D-FDTD)...     

Plasmonic-Induced Transparency and Slow-Light Effect Based on Stub Waveguide with Nanodisk Resonator

Plasmonics - A compact plasmonic system based on a stub metal-insulator-metal (MIM) waveguide coupled with a nanodisk resonator for plasmonic-induced transparency (PIT) has been proposed and...     

Enlargement of the Field of View and Maintenance of a High Signal-to-Noise Ratio Using a Two-Element High-T(c) Superconducting Array in a 3T MRI

This study examines the enlargement of the field of view (FOV) and the maintenance of a high signal-to-noise ratio (SNR) through the use of two high-temperature superconducting (HTS) resonators in a 3T MRI. Two Bi(2)Sr(2)Ca(2)Cu(3)O(x) (Bi-2223) surface resonators, each of 4-cm diameter, were used in a 3T MRI. Professionally made copper resonators operate at 300 K, but each Bi-2223 resonator, operated at 77 K and demonstrated a 3.75 fold increase in SNR gain. For the same scanning time, the SNR of the images of a rat's brain and back, obtained using two small Bi-2223 surface resonators, was higher than that obtained using a single 8-cm surface resonator.     

Characteristics of Plasmonic Filters with a Notch Located Along Rectangular Resonators

We propose a plasmonic filter with a notch located along a rectangular resonator. The finite difference time domain method is utilized to investigate and analyze the transmission characteristics of the filter. Results reveal that the introduction of the notch affects the first and second resonant modes of the resonator in different manners due to different magnetic field distributions inside the resonator. The evolution of the transmission-peak wavelengths as a function of the notch position with the same total resonator length is given. Effects of geometrical parameters of the notch on peak wavelengths are also studied. The corresponding theoretical model of our proposal is discussed, which agrees well with simulation results.