Coupling Distance Research Articles

Experimental oscillation death in two mutually coupled light-controlled oscillators.

We characterized the synchronous behavior of two mutually coupled light-controlled oscillators to determine their relevant parameters allowing validation of our model that predicts oscillation death for strong coupling. We experimentally verified the predictions mentioned above and identified the critical coupling (distance) for which oscillation death starts to manifest itself.

Validation of Wireless Power Transfer by using 3D Representation of Magnetically Coupled Resonators Considering Peak Efficiency

This paper focuses on wireless power transfer system based on magnetic resonance coupling which involves creating a resonance and transferring the power without radiating electromagnetic wave outwith the critical distance. Modelling with Ansys<SUP>®</SUP> Maxwell 3D software provides the means to observe the main field quantities with its post-processing capability. Therefore mathematical expressions of optimal coupling coefficients are analyzed by considering mutual coupling model which is presented along with a derivation of key system identifiers such as transmission distance, characteristic impedance and resonance frequency. The effectiveness of the system is analyzed by exciting the resonators with sinusoidal voltage source. Ansys<SUP>®</SUP> Maxwell 3D software is utilized to solve equivalent circuit and also to calculate mutual inductance and characteristic impedance according to air gap variations. Resonance frequency is a key parameter in system design whose value can be changed according to distance between resonators. The peak efficiency is analyzed depending on different air gap values for various characteristic impedances at optimum resonance frequency. In this study, modelling resonators in 3D has been constituted correspondingly. The approach demonstrated in this paper allows fixed load receiver to be moved to different orientation within the range of critical coupling distance and approximately efficiency of 70 %.

Active control of an edge-mode-based plasmon-induced absorption sensor.

We investigate the formation and evolution of plasmon-induced absorption (PIA) effect in a three-dimensional graphene waveguide structure. The PIA window is formed by near-field coupling of the graphene edge mode, the extremely destructive interference between the radiative mode and sub-radiative mode of graphene nanoribbons. The resonance intensity has a significant dependence on the coupling distance between the graphene nanoribbons. At the same time, it is particularly sensitive to the refractive index of the environment, which is promising for sensing devices. In addition, the resonant wavelength can be actively controlled by changing the Fermi energy of graphene. Moreover, it can be seen that the group time delay of the PIA window reaches -0.28 ps, which is a good candidate for ultrafast light application. Finally, additional graphene nanoribbons can also form a double-channel PIA window. Our work may provide an excellent platform for controlling the optical transmission of highly integrated plasmonic components.

Variations in Ca2+ Influx Can Alter Chelator-Based Estimates of Ca2+ Channel-Synaptic Vesicle Coupling Distance.

The timing and probability of synaptic vesicle fusion from presynaptic terminals is governed by the distance between voltage-gated Ca2+ channels (VGCCs) and Ca2+ sensors for exocytosis. This VGCC-sensor coupling distance can be determined from the fractional block of vesicular release by exogenous Ca2+ chelators, which depends on biophysical factors that have not been thoroughly explored. Using numerical simulations of Ca2+ reaction and diffusion, as well as vesicular release, we examined the contributions of conductance, density, and open duration of VGCCs, and the influence of endogenous Ca2+ buffers on the inhibition of exocytosis by EGTA. We found that estimates of coupling distance are critically influenced by the duration and amplitude of Ca2+ influx at active zones, but relatively insensitive to variations of mobile endogenous buffer. High concentrations of EGTA strongly inhibit vesicular release in close proximity (20-30 nm) to VGCCs if the flux duration is brief, but have little influence for longer flux durations that saturate the Ca2+ sensor. Therefore, the diversity in presynaptic action potential duration is sufficient to alter EGTA inhibition, resulting in errors potentially as large as 300% if Ca2+ entry durations are not considered when estimating VGCC-sensor coupling distances.SIGNIFICANT STATEMENT The coupling distance between voltage-gated Ca2+ channels and Ca2+ sensors for exocytosis critically determines the timing and probability of neurotransmitter release. Perfusion of presynaptic terminals with the exogenous Ca2+ chelator EGTA has been widely used for both qualitative and quantitative estimates of this distance. However, other presynaptic terminal parameters such as the amplitude and duration of Ca2+ entry can also influence EGTA inhibition of exocytosis, thus confounding conclusions based on EGTA alone. Here, we performed reaction-diffusion simulations of Ca2+-driven synaptic vesicle fusion, which delineate the critical parameters influencing an accurate prediction of coupling distance. Our study provides guidelines for characterizing and understanding how variability in coupling distance across chemical synapses could be estimated accurately.

Micromixing performance and the modeling of a confined impinging jet reactor/high speed disperser

In order to get a better micromixing performance, an intensification reactor that couples a confined impinging jet reactor and high speed disperser (CIJR-HSD) was designed. The influences of operating and structural parameters on the micromixing performance were investigated by using the iodide-iodate reaction system. The results showed that the segregation index decreased with the increase of both the rotational speed and the number of rotors; whilst there was little influence due to both inlet flow rate and the presence of packing. The coupling distance between the centre of the CIJR and the first rotor of the HSD also had a non-negligible effect on segregation index. The micromixing time was determined by the Engulfment model, and could also be evaluated by the energy dissipation model based on fluid energy transformation. It was found that the micromixing time for the CIJR-HSD device was in the range of 0.1–0.3 ms, while that for a single CIJR was in the range of 0.35–0.5 ms.

Fast and efficient wireless power transfer via transitionless quantum driving

Shortcut to adiabaticity (STA) techniques have the potential to drive a system beyond the adiabatic limits. Here, we present a robust and efficient method for wireless power transfer (WPT) between two coils based on the so-called transitionless quantum driving (TQD) algorithm. We show that it is possible to transfer power between the coils significantly fast compared to its adiabatic counterpart. The scheme is fairly robust against the variations in the coupling strength and the coupling distance between the coils. Also, the scheme is found to be reasonably immune to intrinsic losses in the coils.

Plasmon-induced absorption and its applications for fast light and sensing based on double-stub resonators

We propose a double-stub resonator (DSR) end-coupled two metal–insulator–metal waveguides. The plasmon-induced absorption (PIA) effect, in which transmission characteristics completely differ from those of a plasmon-induced transparency system, is demonstrated in the DSR system. The performance of the proposed structure is investigated using the finite-difference time-domain method. A transmission dip occurs at the former peak wavelength of the DSR, whereas two transmission peaks appear around the window. The influences of coupling distance and stub length on PIA peaks are investigated and analyzed in detail. Abnormal dispersions can be achieved with the windows based on the analysis of phase responses. Such dispersions can be used for fast light applications in a plasmonic waveguide. Furthermore, sensitivities of 560 nm/refractive index unit (RIU) and 615 nm/RIU, with a sensing medium filling in the double-stub cavity, can be achieved for the two PIA peaks. Result approximates twice as much as the sensing medium filling in one stub of the double-stub cavity. In addition, PIA also manifests in the triple-stub resonator. The results indicate the potential applications of DSR in filtering and sensing.

Multiple plasmonically induced transparency for chip-scale bandpass filters in metallic nanowaveguides

We propose and investigate a new kind of bandpass filters based on the plasmonically induced transparency (PIT) effect in a special metal–insulator–metal (MIM) waveguide system. The finite element method (FEM) simulations illustrate that the obvious PIT response can be generated in the metallic nanostructure with the stub and coupled cavities. The lineshape and position of the PIT peak are particularly dependent on the lengths of the stub and coupled cavities, the waveguide width, as well as the coupling distance between the stub and coupled cavities. The numerical simulations are in accordance with the results obtained by the temporal coupled-mode theory. The multi-peak PIT effect can be achieved by integrating multiple coupled cavities into the plasmonic waveguide. This PIT response contributes to the flexible realization of chip-scale multi-channel bandpass filters, which could find crucial applications in highly integrated optical circuits for signal processing.

A Method to Identify Blasting-Induced Damage Zones in Rock Masses Based on the P-Wave Rise Time

Abstract Blasting-induced damage zones in rock masses are commonly identified by changes in the ratio of the P-wave velocities before and after blast. In ultrasonic tests, water is usually adopted as the coupling medium. As the ultrasonic wave propagates in the aqueous medium, the measured P-wave velocity will be affected by the water coupling distance between the transducer and the wall of the test hole. However, compared to the rock material, due to the lower dispersivity of the aqueous medium, the P-wave rise time is nearly unaffected by water coupling distance. The method based on P-wave rise time is as simple and feasible as the method based on P-wave velocity while employed in field testing. Furthermore, when P-wave rise time is used to detect blasting-induced damage zones, the measured data are in less variability and greater reliability than that acquired from the method based on P-wave velocity. As a result, while the P-wave velocity data are highly variable, the damage zone is difficult to discriminate, but it can be relatively easily discriminated using the P-wave rise time.

Analysis of nonreciprocal noise based on mode splitting in a high-Q optical microresonator

The whispering gallery mode optical microresonator offers a high quality factor, which enables it to act as the core component of a high sensitivity resonator optic gyro; however, nonreciprocal noise limits its precision. Considering the Sagnac effect, i.e. mode splitting in high-quality optical micro-resonators, we derive the explicit expression for the angular velocity versus the splitting amount, and verify the sensing mechanism by simulation using finite element method. Remarkably, the accuracy of the angular velocity measurement in the whispering gallery mode optical microresonator with a quality factor of 108 is 106 °/s. We obtain the optimal coupling position of the novel angular velocity sensing system by detecting the output transmittance spectra of different vertical coupling distances and axial coupling positions. In addition, the reason for the nonreciprocal phenomenon is determined by theoretical analysis of the evanescent distribution of a tapered fiber. These results will provide an effective method and a theoretical basis for suppression of the nonreciprocal noise.

Sensing performance analysis on Fano resonance of metallic double-baffle contained MDM waveguide coupled ring resonator

Based on the transmission property and the photon localization characteristic of the surface plasmonic sub-wavelength structure, a metallic double-baffle contained metal-dielectric-metal (MDM) waveguide coupled ring resonator is proposed. Like the electromagnetically induced transparency (EIT), the Fano resonance can be achieved by the interference between the metallic double-baffle resonator and the ring resonator. Based on the coupled mode theory, the transmission property is analyzed. Through the numerical simulation by the finite element method (FEM), the quantitative analysis on the influences of the radius R of the ring and the coupling distance g between the metallic double-baffle resonator and the ring resonator for the figure of merit (FOM) is performed. And after the structure parameter optimization, the sensing performance of the waveguide structure is discussed. The simulation results show that the FOM value of the optimized structure can attain to 5.74×104 and the sensitivity of resonance wavelength with refractive index drift is about 825 nm/RIU. The range of the detected refractive index is suitable for all gases. The waveguide structure can provide effective theoretical references for the design of integrated plasmonic devices.

Investigating the Characteristics of a Double Circular Ring Resonators Slow Light Device Based on the Plasmonics-Induced Transparency Coupled with Metal-Dielectric-Metal Waveguide System

We have numerically investigated an analog of electromagnetically induced transparency (EIT) in a metal-dielectric-metal (MDM) waveguide bend. The geometry consists of two asymmetrical stubs extending parallel to an arm of a straight MDM waveguide bend. Finite-difference time-domain simulations show that a transparent window is located at 1550 nm, which is the phenomenon of plasmonic-induced transparency (PIT). Signal wavelength is assumed to be 820 nm. The velocity of the plasmonic mode can be largely slowed down while propagating along the MDM bends. Multiple-peak plasmon-induced transparency can be realized by cascading multiple cavities with different lengths and suitable cavity-cavity separations. Large group index up to 73 can be obtained at the PIT window. Our proposed configuration may thus be applied to storing and stopping light in plasmonic waveguide bends. In addition, the relationship between the transmission characteristics and the geometric parameters including the radius of the nano-ring, the coupling distance, and the deviation length between the stub and the nano-ring is studied in a step further. The velocity of the plasmonic mode can be largely slowed down while propagating along the MDM bends. For indirect coupling, formation of transparency window is determined by resonance detuning, but, evolution of transparency is mainly attributed to the change of the coupling distance. Theoretical results may provide a guideline for control of light in highly integrated optical circuits. The characteristics of our plasmonic system indicate a significant potential application in integrated optical circuits such as optical storage, ultrafast plasmonic switch, highly performance filter, and slow light devices.

Self-Regulated Reconfigurable Voltage/Current-Mode Inductive Power Management

A reconfigurable power management structure for inductive power delivery has been proposed by adaptively employing either resonant voltage or current mode (VM or CM) to improve the inductive power transmission performance against coils’ coupling distance (d), orientation ( $\phi $ ), and load impedance (R L ) variations. At the presence of these variations, unlike conventional VM and CM power managements with poor voltage- and power-conversion efficiencies (VCE and PCE), respectively, the proposed voltage/current-mode inductive power management (VCIPM) chip can achieve high VCE by automatically switching to CM when the receiver (Rx) coil voltage (V R ) is smaller than the required load voltage (V L ), and achieve high PCE by operating in VM when V R > V L . In addition, since VM and CM are only suitable for small and large R L within the range of hundreds of ohms and above, respectively, the VCIPM chip can extend the R L range. The VCIPM chip also eliminates the need for two off-chip capacitors by performing rectification, regulation, and over-voltage protection (OVP) in one step with one off-chip capacitor. In VM, intentional reverse current is employed for both voltage regulation and OVP, while the Rx coil switching frequency (f sw ) is adjusted for voltage regulation in CM. The theory behind the proposed VCIPM structure has been presented and validated by simulations and measurements. A VCIPM prototype chip was fabricated in a 0.35- $\mu \text{m}$ 2P4M standard CMOS process occupying 0.52-mm2 active area. In measurements, the VCIPM chip, operating at 1 MHz, achieved a high VCE of 4.1 V/V for R L of 100 $\text{k}\Omega $ by operating in CM with fsw = 166.6 kHz, and extended d and $\phi $ from 6 to 13.5 cm (125%) and 30° to 75° (150%), respectively, compared to its VM counterpart by adaptively switching from VM to CM.

Tunable plasmon-induced absorption effects in a graphene-based waveguide coupled with graphene ring resonators

In this paper, we propose a structure composed of two graphene waveguides and dual coupled graphene ring resonators (GRRs) to achieve a plasmon-induced absorption (PIA) effect. A three-level plasmonic system and a temporal coupled mode theory (CMT) are utilized to verify the simulation results. Moreover, a double-window-PIA effect can be conveniently attained by introducing another GRR with proper parameters to meet more specific acquirement in optical modulation process. The pronounced PIA resonances can be tuned in a number of ways, such as by adjusting the coupling distance between the GRRs and the couplings between the GRR and the waveguide, and tuning the radius and the Fermi energy of the GRRs. Besides, the produced PIA effect shows a high group delay up to −1.87 ps, exhibiting a particularly prominent fast-light feature. Our results have potential applications in the realization of THz-integrated spectral control and graphene plasmonic devices such as sensors, filters, ultra-fast optical switches and so on.

Tunable plasmonic band-pass filter based on Fabry–Perot graphene nanoribbons

A plasmonic band-pass filter (BPF) structure is designed and proposed in this research. The filter structure includes two graphene nanoribbon (GNR) waveguides laterally coupled to three perpendicular GNRs that forms a Fabry–Perot resonator (FPR). The transmission spectrum of the proposed structure can be tuned in an efficient and flexible fashion by making adjustments on the overall geometrical structure and its chemical potential, as well. Geometry can be modified in the design step, even as a real-time controlling voltage can be applied as a chemical potential tuner. The coupling distances between GNR waveguides and GNRs of the FPR and also coupling distances among GNRs of FPR themselves strongly affect the transmission spectrum and bandwidth characteristics of the BPF. Transmission spectrum with one, two, or three peaks can be achieved by adjusting the distances between GNRs of the FPR, even as other geometrical adjustments and/or chemical potential tuning shifts the spectrum to the desired frequency range. The results achieved by 3D finite-difference time-domain (3D-FDTD) method verify the capability of the proposed structure to be applied in applications used in plasmonic and nano-optoelectronics devices.

Theoretical Analysis of Plasmon-Induced Transparency in MIM Waveguide Bragg Grating Coupled With a Single Subradiant Resonator

A plasmon-induced transparency (PIT) spectral response in an ultracompact plasmonic structure composed of a metal–insulator–metal waveguide Bragg grating coupled with an air rectangle cavity is proposed, and the corresponding transmission characteristics are investigated theoretically and numerically. By using the transmission line theory (TLT), a remarkable PIT transmission can be proposed in this structure. Moreover, we study the transmission as a function of the coupling distance between the air cavity and insulator layer, and we also discuss the transmission as a function of the thickness of air cavity. To validate the correctness of the TLT results, we have compared them with the finite-difference time-domain method. Both of them agree well with each other. Thus, our results can offer a new possibility and important theory analysis for the designs of the optical switching devices, sensors, and slow light devices in highly integrated optical circuits.

Transportation distances and noise sensitivity of multiplicative Lévy SDE with applications

This article assesses the distance between the laws of stochastic differential equations with multiplicative Lévy noise on path space in terms of their characteristics. The notion of transportation distance on the set of Lévy kernels introduced by Kosenkova and Kulik yields a natural and statistically tractable upper bound on the noise sensitivity. This extends recent results for the additive case in terms of coupling distances to the multiplicative case. The strength of this notion is shown in a statistical implementation for simulations and the example of a benchmark time series in paleoclimate.

Class E Power Amplifier Design and Optimization for the Capacitive Coupled Wireless Power Transfer System in Biomedical Implants

The capacitive coupled wireless power transfer (CCWPT) operating at megahertz (MHz) frequency is broadly considered as the promising solution for low power biomedical implants. The class E power amplifier is attractive in MHz range wireless power transfer (WPT) applications due to zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS) properties. The existing design of class E amplifier is investigated only for inductive resonant coupled (IRC) WPT systems; the modelling and optimization of the class E amplifier for CCWPT systems are not deliberated with load variation. Meanwhile, the variations in the coupling distance and load are common in real time applications, which could reduce the power amplifier (PA) efficiency. The purpose of this paper is to model and optimize the class E amplifier for CCWPT systems used in MHz range applications. The analytical model of PA parameters and efficiency are derived to determine the optimal operating conditions. Also, an inductive-capacitive-inductive (LCL) impedance matching network is designed for the robust operation of the PA, which improves the efficiency and maintains required impedance compression. The maximum efficiency of the proposed design reached up to 96.34% at 13.56 MHz and the experimental results are closely matched with the simulation.

Graphene-based tunable terahertz filter with rectangular ring resonator containing double narrow gaps

A plasmonic band-pass filter based on graphene rectangular ring resonator with double narrow gaps is proposed and numerically investigated by finite-difference time-domain (FDTD) simulations. For the filter with or without gaps, the resonant frequencies can be effectively adjusted by changing the width of the graphene nanoribbon, the coupling distance and chemical potential of graphene. In addition, by introducing narrow gaps in the rectangular ring resonators, it shows the single frequency filtering effect. Moreover, the structure also shows high sensitivity for different surrounding mediums. This work provides a novel method for designing all-optical integrated components in optical communication.

Analogue of electromagnetically-induced-transparency based on graphene nanotube waveguide

A graphene-based nanotube waveguide system is proposed and designed to realize the analogue of electromagnetically-induced-transparency. The two nanotubes act as side coupled cavity rings which can be treated as the bright and dark resonators. By mimicking the quantum nonlinear optical interference, the light at resonant frequency makes the opaque system transparent. Conveniently, the working transparency window can be dynamically controlled by shifting the Fermi energy level of graphene without refabricating the device. Furthermore, the shape of the transmission spectrum can be tuned either by adjusting the waveguide coupling distance or by the cavity ring coupling distance. If the ring radius gets bigger, higher order of modes are excited in the dark resonator consequently. Meaningfully, the light travels at resonant frequency can be efficiently slowed down and the highest group delay reaches 25 ps. In the end, some concerns about the practical realization of such device are discussed. The structure may find potential applications in nano technology or light storage field.