Multilayer Resonator Research Articles

High-Q BSW-whispering gallery modes in periodic multi-layer microring resonator

We propose a kind of ultrasensitive sensing structure based on Bloch surface wave(BSW)-whispering gallery mode localized on the surface between the sensed medium and the multi-layer microring. By exploiting low-loss and high percentage of energy extending into the sensed medium properties of BSW and high quality factor property of whispering gallery modes, this BSW-whispering gallery mode possesses a high percentage of energy in the sensed medium around 55% and a high quality factor on the order of 105. As a potential application, the BSW-whispering gallery mode could be used for sensing with a sensitivity high up to 400 nm per refractive index unit, and a significantly improved FOM about 1.88×105.

All-optical 6- and 8-channel demultiplexers based on photonic crystal multilayer ring resonators in Si/C rods

In this paper, we employed multilayer ring resonators in a silicon rod base structure to realize 6-channel and 8-channel demultiplexers based on two-dimensional photonic crystals. Both the main rings and basic structures are composed of silicon rods, and the interior rings of the multilayer rings are composed of carbon. Employing silicon and carbon rods of different radii in multilayer ring resonators enhanced the coupling efficiency between the rings and waveguides. The average quality factor and power transmission efficiency were 4320 and 93%, respectively. Crosstalk values from $$-11$$ to −46 dB in conjunction with the mentioned characteristics suggest the use of the device for optical communication applications. The compact size of the proposed structure and the materials used make the proposed demultiplexer suitable for optical integrated circuits.

Multi-resonance tunneling of acoustic waves in two-dimensional locally-resonant phononic crystals

Multi-resonance tunneling of acoustic waves through a two-dimensional phononic crystal (PC) is demonstrated by substituting dual Helmholtz resonators (DHRs) for acoustically-rigid scatterers in the PC. Due to the coupling of the incident waves with the acoustic multi-resonance modes of the DHRs, acoustic waves can tunnel through the PC at specific frequencies which lie inside the band gaps of the PC. This wave tunneling transmission can be further broadened by using the multilayer Helmholtz resonators. Thus, a PC consisting of an array of dual/multilayer Helmholtz resonators can serve as an acoustic band-pass filter, used to pick out acoustic waves with certain frequencies from noise.

Multilayered surface plasma resonance waveguide sensing device

In recent years, surface plasma resonance (SPR) technology for the preparation of multifunctional detection chips has drawn considerable research attention. This study designs a multilayered SPR waveguide sensing device based on a metal medium that features moderate temperature and humidity. The surface plasma is stimulated using a Kretschmann-type structure and a single temperature and humidity chip of SPR technology to achieve multifunctional detection. The sensing principle of the proposed device is based on SPR angle and the environmental relationship between relative humidity and temperature. Characteristic analysis also verifies that SPR with an incident wavelength of 632nm can be accomplished by the basic linear relationship between the resonance angle and SiO2 refractive inde. The accuracy of dual-channel sensors is higher than that of single-channel sensors. The metal layer for gold channel sensitivity can reach 7000nm/RIU. The dual-channel sensor designed in this study exhibits low refractive index, temperature, and humidity and can thus achieve improved sensitivity.

Ferromagnetic resonance and interlayer exchange coupling in magnetic multilayers with compositional gradients

Ferromagnetic resonance (FMR) in magnetic multilayers of type F1/f/F2, where two strongly ferromagnetic layers F1 and F2 are separated by a weakly magnetic spacer f with a compositional gradient along its thickness, is investigated. The method allows to detect the weak signal from the spacer in additional to the more pronounced and readily measured signal from the outer strongly-magnetic layers, and thereby study the properties of the spacer as well as the interlayer exchange interaction it mediates. Variable temperature FMR measurements, especially near the relevant Curie points, reveal a rich set of properties of the exchange interactions in the system. The obtained results are useful for designing and optimizing nanostructures with thermally-controlled magnetic properties.

Vibration of a multilayer graphene sheet under layerwise tension forces

The present work is inspired by the fact that tension enforced by external force applied directly to the outermost layers of a (usually incommensurate) multilayer graphene sheet cannot be effectively transferred to all inner layers due to interlayer sliding, and therefore tension force in inner layers can be much lower than the tension force in the outermost layers. In this paper, a three-beam model is presented to study vibration of a multilayer graphene sheet under layerwise tension forces. In contrast to the commonly used single-beam model which assumes that tension in all layers of a multilayer graphene sheet are identical, the present model treats the top and bottom layers as two beams, and all other inner layers together as another beam which has different tension force than the top and bottom beams. Our results indicate that actual tensile stress/strain in the outmost singlelayers of a multilayer graphene sheet can be much (for instance, almost ten times, for specific examples discussed here) higher than that estimated by the widely used single-beam model, and the latter can badly underestimate actual tensile stress/strain of multilayer graphene resonators. In addition, at least for typical examples discussed here, the present model shows that vibrational frequencies of a multilayer graphene sheet are largely determined by the total tension, and the distribution of the total tension over different layers does not make a huge impact to vibrational frequencies of multilayer graphene resonators. Based on this conclusion, an explicit formula is given for resonant frequencies of multilayer graphene sheets under layerwise tension forces although the actual maximum tension depends on how total tension is distributed over all layers.

Mode excitation in the microstrip slot‐coupled three‐layer hemispherical dielectric resonator antenna

In this study, a microstrip slot-coupled multilayer dielectric resonator antenna (DRA) structure is rigorously analysed from the modal perspective, taking into account all layers. The choice of layer permittivities of the multilayer structure to reduce the Q-factor and obtain optimum bandwidth performance of the antenna is outlined. Next, the mechanism of bandwidth enhancement for the centred and offset slots is examined taking into account the excited modes in the structure. It is found that while the centred slot couples to one DRA mode, an offset slot can couple to multiple DRA modes together with the slot mode. Thereafter, the excitation efficiency of modes in the multilayer DRA structure is highlighted to thoroughly characterise the modal contribution in the coupling behaviour for the centred and offset-slots.

Sensitivity study of multilayer thin-film bulk acoustic resonator for mass sensor application

The sensitivity of multilayer thin-film bulk acoustic resonators (MTFBARs) used as mass sensors is investigated. MTFBAR sensors with the structure of a mass-sensitive layer/electrode layer/piezo layer/electrode layer were used. Two methods, one using electric impedance and the other displacement, were adopted for the determination of sensitivity. Simulation results show that the two methods agree well, and the characteristic acoustic impedance and thickness of the non-piezo layers strongly affect mass sensitivity. It was found that high acoustic impedance in the non-piezo layer is not helpful for sensitivity improvement. Sensitivity is improved by choosing an appropriate thickness for the low acoustic impedance non-piezo layer, and the maximum sensitivity can be obtained by choosing suitable thickness combinations for the layers. Moreover, it was found that MTFBAR quality factor and sensitivity are simultaneously improved by adopting a high-quality-factor non-piezo layer with low acoustic impedance for an air working environment, whereas a balance between quality factor and sensitivity is found through optimization of the non-piezo layers for a water working environment. These results can be used for the design and application of MTFBAR mass sensors.

Force sensitivity of multilayer graphene optomechanical devices.

Mechanical resonators based on low-dimensional materials are promising for force and mass sensing experiments. The force sensitivity in these ultra-light resonators is often limited by the imprecision in the measurement of the vibrations, the fluctuations of the mechanical resonant frequency and the heating induced by the measurement. Here, we strongly couple multilayer graphene resonators to superconducting cavities in order to achieve a displacement sensitivity of 1.3 fm Hz−1/2. This coupling also allows us to damp the resonator to an average phonon occupation of 7.2. Our best force sensitivity, 390 zN Hz−1/2 with a bandwidth of 200 Hz, is achieved by balancing measurement imprecision, optomechanical damping, and measurement-induced heating. Our results hold promise for studying the quantum capacitance of graphene, its magnetization, and the electron and nuclear spins of molecules adsorbed on its surface.

Selective excitation of eigenmodes in a multilayer thin film resonator on bulk acoustic waves

We consider a method of control over the operating frequency of a resonator on bulk acoustic waves, which is based on the selective excitation of eigenmodes. The frequency switching is achieved by using several layers of a ferroelectric in the paraelectric state and applying a control voltage of appropriate magnitude and polarity to each layer. The principle of selectivity is formulated and the criterion function is defined, which ensure the most effective excitation of a selected eigenmode with the possible suppression of parasitic modes. An example of using this function for a resonator switched between four eigenmodes is presented.

Magneto-induced Fano-like cavity interference in three-dimensional metamaterials

Fano-like cavity interference due to magneto-inductive coupling in metamaterial structure is demonstrated via a double Fabry–Perot cavity (DFPC) that consists of stacked multi-layered resonators. The induced magnetic field based destructive interference is observed in the transmission response of the DFPC system, which exhibits the Fano line shaped resonance. The retrieved real and imaginary parts of effective permeability and permittivity indicate strong magneto-induced dispersion with a group delay leading to the slow light effect. This finding provides an interesting mechanism to excite Fano resonances in metamaterial systems via magnetic interaction between resonators, which may enable new devices for slow light and sensing applications.

Multilayer with periodic grating based high performance SPR waveguide sensor

We propose a high performance periodic grating coupled multi-layered surface plasmon resonance (SPR) waveguide based on Al+Au. High sensitivity is obtained by using grating filled with silver instead of air. Further sensor's performance is analysed by optimising width and thickness of SPR active metal layer as well as grating period also. Using finite difference time domain (FDTD) method, we have shown that sensitivity and detection accuracy can be improvised using appropriate multi-layered grating configuration.

Negative nonlinear damping of a multilayer graphene mechanical resonator

We experimentally investigate the nonlinear response of a multilayer graphene resonator using a superconducting microwave cavity to detect its motion. The radiation pressure force is used to drive the mechanical resonator in an optomechanically induced transparency configuration. By varying the amplitudes of drive and probe tones, the mechanical resonator can be brought into a nonlinear limit. Using the calibration of the optomechanical coupling, we quantify the mechanical Duffing nonlinearity. By increasing the drive force, we observe a decrease in the mechanical dissipation rate at large amplitudes, suggesting a negative nonlinear damping mechanism in the graphene resonator. Increasing the optomechanical backaction further, we observe instabilities in the mechanical response.

Moisture estimation of transformer pressboard by micro-strip ring resonator at GHz frequencies

Increased moisture content (MC) is considered as one of the main factors for the failure of transformer insulation. This paper presents a method of estimating the MC of a transformer pressboard insulation based on the relative permittivity and loss tangent measurements performed at GHz using a multi-layer micro-strip ring resonator. It was fabricated on a material of known dielectric properties and the sample to be tested (i.e. pressboard) was placed on the ring structure. The dielectric properties, namely loss tangent and permittivity, of the sample were then estimated by measuring the S 21 transmission characteristics of the ring structure using a vector network analyzer. The technique was validated using a test sample of known dielectric properties. Additionally the results were compared with traditional frequency domain dielectric spectroscopy (FDS) measurements conducted at 1 mHz −1 kHz. The measurements were performed on oil impregnated and non-impregnated pressboard samples having different MCs conditioned by drying and/or wetting processes. The actual MC of the pressboard samples were obtained by weight measurements. It was found that the resonance frequency increased when the MC was reduced. Furthermore, a positive non-linear relation could be observed between the MC and both the relative permittivity and the loss tangent. It can be concluded that the proposed method could be used to estimate the MC of pressboards.

Graphene-based multilayer resonance structure to enhance the optical pressure on a Mie particle

We theoretically investigate the optical force exerted on a Mie dielectric particle in the evanescent field of a graphene-based resonance multilayer structure using the arbitrary beam theory and the theory of multilayer films. The resonance structure consists of several thin films including a dielectric film ( MgF 2 ), a metal film (silver or gold), and several graphene layers which are located on a prism base. The effects of the metal film thickness and the number of graphene layers on the optical force are numerically investigated. The thickness of the metal layer and the number of graphene layers are optimized to reach the highest optical force. The numerical results show that an optimized composition of graphene and gold leads to a higher optical force compared to that of the graphene and silver. The optical force was enhanced resonantly by four orders of magnitude for the resonance structure containing graphene and a gold film and by three orders of magnitude for the structure containing graphene and a silver film compared to other similar resonance structures. We hope that the results presented in this paper can provide an excellent means of improving the optical manipulation of particles and enable the provision of effective optical tweezers, micromotors, and microaccelelators.

An affinity triggered MRI nanoprobe for pH-dependent cell labeling

The pH-sensitive affinity pair composed by neutravidin and iminobiotin was used to develop a multilayered Magnetic Resonance Imaging (MRI) nanoprobe responsive to the acidic pH of tumor microenvironment.

Dielectric properties of Sn-substituted lead calcium iron niobate

Sn-substituted lead calcium iron niobate with general formula (Pb0.45Ca0.55)(Fe0.5Nb0.5)1−ySnyO3 and 0.00 ≤ y ≤ 0.15 in the steps of 0.03 were synthesized by using columbite precursor method. XRD spectra from these ceramics reveal a perovskite structure with pseudocubic symmetry. Small amount of pyrochlore phase was obtained decreasing with increasing Sn content up to y = 0.09. The degree of perovskite phase formation and average grain size increased with increase in Sn contents. Dielectric properties were measured in the frequency range 200 kHz to 10 MHz at room temperature and a high relative permittivity of 71.38 and loss tangent of 0.0081 at 10 MHz along with low temperature coefficient of resonant frequency of +7.665 ppm/K for y = 0.09 has been obtained. Obtained results have shown that the substitution of (Fe0.5Nb0.5)4+ by Sn4+ at B-site improves the dielectric properties by reducing the loss tangent and temperature coefficient of resonant frequency. The studied materials are promising candidate for multilayer capacitors, resonators, and filters.

Fabrication and optical characterization of Bragg resonance luminescence porous silicon

The synthesis and characterization of Bragg resonance luminescence porous silicon (BRL PS) exhibiting both optical reflectivity and strong narrow visible photoluminescence (PL) prepared from highly doped n-type silicon wafers through the electrochemical etching are reported. BRL PS showing the luminescence at 702 nm with an excitation wavelength of 400 nm was prepared by applying the current of 360 mA cm−2 for 1.6 s and 75 mA cm−2 for 3.6 s with 50 repeats in etching solution of 1:1 volume mixture of absolute ethanol and aqueous 48% HF. BRL PS exhibited sharp PL peak which reached full width at half maximum of 14 nm, originated from the result of Bragg resonance in PS multilayer. The sharp PL peak at 702 nm of BRL PS is the second-order transmitted luminescence peak by Bragg resonance phenomenon. The simultaneous measurement of reflectivity and luminescence in the BRL PS under an exposure to a vapor flux of acetone showed that a narrow transmitted luminescence based on Bragg resonance in BRL PS quenched as well as the red-shifted by 37 nm of reflection wavelength was observed. A dramatic quenching PL of BRL PS compare to that of the monolayer PS, is probably due to the Bragg resonance effect on luminescence.

Electrical and dielectric studies of substituted holmium based pyrochlore zirconates nanomaterials

The effects of Ge4+ cation substitution on the structure, morphology, electrical and dielectric properties of rare earth pyrochlore oxides (Ho2Zr2-xGexO7, 0.00 ≤ x ≤ 1.0) were investigated. The pyrochlore oxides were prepared by the microemulsion method. The XRD data Ge+4 substituted Ho2Zr2-xGexO7 reveal a cubic structure. Room temperature DC electrical resistivity increases on increasing the Ge4+ contents. The value of exponent ‘n’ calculated from the plot of log(σ) versus log(ω) ranges 0.78–0.95 suggested that the conduction phenomena in the studied samples pursue hopping conduction. Nyqiust plot (cole–cole plot) was used to study relaxation phenomenon in the material. The visualization of semicircles in plot represent that grain boundary occupies small volume. The dielectric loss with frequency shows resonance peaks. The dielectric losses were stable below 1.3 GHz. Such frequency independent characteristic of the high dielectric constants Ho2Zr2-xGexO7 ceramics and their low dielectric losses make them more attractive in the applications of multilayer ceramic capacitors and resonators. The increase in resistivity with substitution makes these materials suitable for microwave devices.

Zinc Oxide Based Plasmonic Multilayer Resonator: Localized and Gap Surface Plasmon in the Infrared

Using alternative plasmonic materials, we experimentally demonstrate gap plasmon resonances in metal–insulator–metal nanostructures in the near- and mid-infrared wavelength regions utilizing gallium doped zinc oxide as the metallic component and undoped zinc oxide as the dielectric. We show that similar to metal–insulator–metal resonators previously demonstrated with noble metals, the layered transparent conducting oxide nanodisks support gap surface plasmon resonances characterized by highly confined electromagnetic fields in the dielectric gap. Such resonances can be tailored to desired values by varying the dielectric-layer thickness. Utilizing these observed gap plasmon resonance, we examine the potential of our structure for sensing applications by measuring the surface enhanced infrared absorption of an octadecanethiol layer. The layered nanostructure can detect very weak absorption resonances in nanoscale volumes of absorbing material deposited over the nanodisk resonator.