Parameters Of Coupler Research Articles

Engineering quasi-bound states in the continuum in asymmetric waveguide gratings

Abstract The occurrence of quasi-bound states in the continuum (qBIC) in all-dielectric asymmetric grating waveguide couplers with different degrees of asymmetry under normal light incidence is analysed from the viewpoint of identifying the most promising configuration for realizing the highest quality (Q) factor under the condition of utmost efficiency (i.e. total extinction). Considering asymmetric gratings produced by altering every Nth ridge of a conventional (symmetric) grating coupler, we analyse different regimes corresponding to the interplay between diffractive coupling to waveguide modes and band gap effects caused by the Bragg reflection of waveguide modes. The symmetric and double- and triple-period asymmetric grating couplers are considered in detail for the same unperturbed two-mode waveguide and the grating coupler parameters that ensure the occurrence of total transmission extinction at the same wavelengths. It is found that the highest Q is expected for the double-period asymmetric grating, a feature that we explain by the circumstance that the first-order distributed Bragg resonator (DBR) is realized for this configuration while, for other configurations, the second-order DBR comes into play. Experiments conducted at telecom wavelengths for all three cases using thin-film Al2O3-on-MgF2 waveguides and Ge diffraction gratings exhibit the transmission spectra in qualitative agreement with numerical simulations. Since the occurrence of considered qBIC can be analytically predicted, the results obtained may serve as reliable guidelines for intelligent engineering of asymmetric grating waveguide couplers enabling highly resonant, linear and nonlinear, electromagnetic interactions.

Coupling Dynamics and Linear Polarization Phenomena in Codirectional Polariton Waveguide Couplers

AbstractIn this work, the previous studies investigating the potential of integrated devices using polariton waveguides that form codirectional couplers is extended. For suitable coupler parameters, a transfer of condensates between the arms of the coupler occurs leading to the observation of previously predicted Josephson‐like oscillations. The ability to tune the periodicity of these oscillations opens the way to the design of polaritonic circuits in which the directionality of the signal towards the output terminals can be controlled, for a fixed separation between the arms, varying the coupling length. The response of the devices to linearly polarized excitation is also investigated, delving into the dynamics of linear polarization at the output terminals of long couplers, providing valuable insights into their potential applications, including polariton switches and logic gates with efficient operation. The results are supported by numerical simulations based on the generalized Gross–Pitaevskii equation describing the dynamics of coherent polaritons in spatially non‐uniform systems, reproducing the polariton distribution on the output terminals and an oscillatory dependence of the corresponding emission as a function of the polarization azimuth. How the coupling and the controllable polarization degree of freedom in polariton couplers opens avenues for innovative optical architectures and functionalities is shown here.

Primary side control technique for capacitive power transfer system without any wireless feedback

The output voltage of capacitive power transfer (CPT) system will change if the load resistance is varied. This paper presents a method to regulate the output voltage using a controller that is located on the primary side, known as the primary side control technique. It does not require any additional components and wireless feedback, which lowers the cost and complexity of CPT system compared to the conventional control technique. Instead of directly measuring the output voltage on secondary side, it is estimated through the measured capacitor voltage on primary side. Modified sine wave control of the full-bridge inverter is adopted to regulate the output voltage. The proposed control technique is validated by the simulation via PSIM software using the practical parameters of capacitive coupler presented in the literature. Simulation results of the output voltage control against the step change in desired output voltage and load resistance indicate the performance of proposed control technique.

Design of Magnetic Coupler for AUV Wireless Charging and Its Electromagnetic Field Simulation

The magnetic coupler is one of the important components of wireless charging system, and its coupling coefficient directly influences the energy transmission efficiency. This paper designs a magnetic coupler for Autonomous Underwater Vehicle(AUV) wireless charging in the marine environment. Firstly, the eddy current effect during energy transmission of the magnetic coupler under seawater conditions is analyzed, and the equivalent model of the wireless charging system is compensated and corrected. Then, the genetic-BP neural network algorithm is used to determine the relevant structural parameters of the magnetic coupler. Finally, the electromagnetic field simulation analysis of the offset phenomenon between the transmitting and receiving sides of the magnetic coupler is carried out based on ANSYS MAXEWLL software.The results show that the coupling coefficient of the magnetic coupler under normal operation is 0.87, and if there is a 10mm radial offset (or 5 ° circumferential offset), the coupling coefficient will decrease to 0.74 (or 0.78), which provides a reference basis for the subsequent offset fault-tolerant design of the AUV wireless charging system.

Design of a mixed load‐modulation balanced power amplifier with ultra‐extended power back‐off range

SummaryThis paper proposes a mixed design strategy to expand the power back‐off (OBO) range of the pseudo‐Doherty load‐modulation balanced power amplifier (LMBA). An asymmetric LMBA configuration is employed to increase the OBO range. The two PA branches of the balanced PA operate in different class‐C modes, thereby obtaining two OBO points. Further, an asymmetrical coupler is also introduced into the asymmetrical LMBA architecture to expand the OBO. Here, the relationship between the OBO and coupler's parameters and asymmetrical configuration parameters is built. The behaviors of the proposed PA as a function of input power are derived when several representative parameters are chosen. To validate the proposed topology, a PA with an OBO of 15 dB operating across 3.4–3.6 GHz is designed, fabricated, and tested. Measurements illustrate that the PA can deliver a saturated output power of 43.6–44.5 dBm with a drain efficiency ranging from 70% to 72%. Drain efficiencies are between 50% and 68% at the OBO of 15 dB. The LMBA implemented here shows state‐of‐the‐art performance in terms of the OBO range.

Grating couplers for efficient integration of surface-emitting blue lasers and silicon nitride waveguide

We report here a theoretical investigation on high efficiency grating coupling for surface emitting blue lasers integrated with silicon nitride (Si3N4) waveguide. DBRs (distributed Bragg reflectors) were introduced into the design which located at the upper and one side of the Si3N4 grating coupler region, and oxide buffer layers was also incorporated simultaneously. By optimizing the grating coupler parameters and the DBR structure, the configuration can be adapted for single polarization or TE/TM simultaneous coupling. The coupling efficiency for TE polarization can reach 72.4 %, and the polarization-independent coupling efficiency of 48 % at vertical incidence was also achieved. This work presents a PIC (photonic integrated circuits) on III-V laser strategy for visible light PICs and innovative applications based on blue laser integrated devices.

An Optical 1×4 Power Splitter Based on Silicon-Nitride MMI Using Strip Waveguide Structures.

This paper presents a new design for a 1 × 4 optical power splitter using multimode interference (MMI) coupler in silicon nitride (Si3N4) strip waveguide structures. The main functionality of the proposed design is to use Si3N4 for dealing with the back reflection (BR) effect that usually happens in silicon (Si) MMI devices due to the self-imaging effect and the higher index contrast between Si and silicon dioxide (SiO2). The optimal device parameters were determined through numerical optimizations using the beam propagation method (BPM) and finite difference time domain (FDTD). Results demonstrate that the power splitter with a length of 34.6 μm can reach equal distribution power in each output port up to 24.3% of the total power across the O-band spectrum with 0.13 dB insertion loss and good tolerance MMI coupler parameters with a shift of ±250 nm. Additionally, the back reflection range over the O-band was found to be 40.25-42.44 dB. This demonstrates the effectiveness of the incorporation using Si3N4 MMI and adiabatic input and output tapers in mitigating unwanted BR to ensure that a good signal is received from the laser. This design showcases the significant potential for data-center networks, offering a promising solution for efficient signal distribution and facilitating high-performance and reliable optical signal routing within the O-band range. By leveraging the advantages of Si3N4 and the MMI coupler, this design opens possibilities for advanced optical network architectures and enables efficient transmission of optical signals in the O-band range.

A Dual-Sided LCLC Topology for AGV Wireless Charging System With Low Leakage EMF

The leakage electromagnetic field (EMF) generated during the wireless charging for automatic guidance vehicle will affect the regular operation of communication equipment and human safety. To reduce the leakage EMF, a dual-sided LCLC topology is introduced and optimized. The core idea is to construct the currents opposite to that flowing through the power transmission coils on primary and secondary sides, respectively. On this basis, connecting the shielding coils in the reverse current branches can generate the canceling magnetic field opposite to the leakage EMF. Thus, a low leakage magnetic coupler is established via the combination of power transmission coils and shielding coils. To minimize the leakage EMF, the specific parameters of magnetic coupler and dual-sided LCLC topology are optimized, and an experimental prototype is built to verify the shielding effect. The results show that when the output power is 1 kW, the shielding effect reaches 84.70%, and the power transfer efficiency is improved by 0.907%. Moreover, in the case of coil misalignment, there is still over 53.15% shielding effect by using the proposed method.

Auto-Segment Control System With High Spatially Average Power for Dynamic Inductive Power Transfer

This work proposes an auto-segment control system with multiple transmitters and dual receivers for dynamic inductive power transfer (DIPT) charging. The current of the transmitting coil precisely coupled with the receiver can be enhanced automatically, while the transmitting current will be suppressed when the transmitter is uncoupled with the receiver. Therefore, the electromagnetic interference (EMI) and power loss generated by uncoupled transmitters can be reduced without position detection and switching control. Each receiver includes a power coil and an impedance coil. When the vehicle moves along the road, the impedance coils are utilized to adjust the resonant state of the transmitter, and the power coils operate alternately to maintain a high spatially average power. The relative position and size between transmitters and receivers directly impact the power transfer performance. Therefore, several critical parameters of the magnetic coupler are analyzed and designed to obtain a considerable output power. An around 300W experimental prototype is established to verify the feasibility of the proposed magnetic coupler and design method. Compared to the auto-segment control system with a single receiver, the spatially average power of the proposed system is improved by twice, and the maximum efficiency is 84.9% in a moving period.

Efficient adiabatic-coupler-based silicon nitride waveguide crossings for photonic quantum computing.

Optical integrated quantum computing protocols, in particular using the dual-rail encoding, require that waveguides cross each other to realize, e.g., SWAP or Toffoli gate operations. We demonstrate efficient adiabatic crossings. The working principle is explained using simulations, and several test circuits are fabricated in silicon nitride (SiN) to characterize the coupling performance and insertion loss. Well-working crossings are found by experimentally varying the coupler parameters. The adiabatic waveguide crossing (WgX) outperforms a normal directional coupler in terms of spectral working range and fabrication variance stability. The insertion loss is determined using two different methods: using the transmission and by incorporating crossings in microring resonators. We show that the latter method is very efficient for low-loss photonic components. The lowest insertion loss is 0.18 dB (4.06%) enabling high-fidelity NOT operations. The presented WgX represents a high-fidelity (96.2%) quantum NOT operation.

An LCC‐S compensated wireless power transfer system using receiver‐side switched‐controlled capacitor combined semi‐active rectifier for constant voltage charging with misalignment tolerance

AbstractThe output characteristics of wireless power transfer systems are strongly susceptible to coupling and load variations. To achieve a constant voltage output under varying coupling and load, a voltage regulation method based on a combination of a semi‐active rectifier (SAR) and a switched‐controlled capacitor (SCC) is proposed for the LCC‐S topology. Adjusting the SAR can effectively regulate the voltage, and the introduction of SCC compensates the impedance brought by SAR, ensuring that the resonance condition is fully satisfied at the receiver side. Thus, the proposed wireless power transfer system can achieve zero phase angle over the entire load and coupling range, minimizing reactive power losses. This control method only needs to collect the signal from the receiver side, which enables single‐side control as well as avoids the wireless communication. The situation of coupler parameter drift due to misalignment is also considered. Even if the self‐inductance changes, the zero phase angle can be guaranteed on the receiving side by adjusting the SCC, and the zero voltage switching of the transmitter side can still be achieved. The principle prototype of 3 kW is constructed and the experimental results prove the effectiveness of the proposed method.

ANALYSIS OF SOME GEOMETRIC PARAMETERS OF THE INDUCTIVE COUPLER INTENDED FOR HIGH POWER WIRELESS SYSTEMS

One of the essential components of a wireless high-power transfer system for heavy-duty electric vehicles is the inductive coupler. The efficiency of the wireless power transfer system strongly depends on the geometric parameters of the inductive coupler, which in turn have an important effect on the electromagnetic parameters of the whole system. The transmitting (Tx) and receiving (Rx) coils of the inductive coupler proposed in this paper have a Double-D planar structure and are located on magnetic cores made of magnetic concrete (Tx) and ferrite (Rx), respectively. The study of the parameters of the inductive coupler was carried out with the help of the finite element method, using the Flux ® field calculation software package.

Vortex-frequency-comb generation assisted by PT -symmetric ring resonators

We study propagation of optical vortices (OVs) in coupled parity-time ($\mathcal{P}\mathcal{T}$) symmetric multimode fibers with equal gain and loss. We show that this system has two second-order exceptional points (EPs) of spectral branches confluence where the degenerate modes are odd and even Laguerre-Gaussian (LG) modes. We study the evolution of an arbitrary incoming superposition of LG modes with the same orbital index in such a coupler. We prove that if the loss parameter exceeds its value in the lowest-lying EP, in the limit of the large coupler's length the outcoming field tends to the same attractor state depicted on the orbital Poincar\'e sphere (PS) by the orbital ``black hole.'' We show that localization of such a ``black hole'' on the PS does not change with variations of loss parameter beyond its value at the lowest EP, which can be called the pinning of the orbital ``black hole.'' We also demonstrate that the fiber ring resonator based on such a coupler can generate an optical vortex frequency comb (FC) far from the EP. The mechanism of such generation is not connected with any nonlinearity in the system. We determine the coupler's parameters under which such generation is feasible. This property can be useful for optimizing fiber-based orbital angular momentum communications.

Circular Capacitive Coupler With Multilayer Interleaving for Stable Output

Capacitive power transfer (CPT) is able to utilize the benefits of electric field and offers an alternate wireless charging solution. However, the basic capacitive couplers usually suffer from the misalignment issue. The coupler parameter shift leads to dramatic output perturbation. In order to stabilize the output, three types of coupling (mutual, self, and cross) are defined to simplify the coupler structure evaluation, and a circular capacitive coupler (CCC) is optimized to stabilize the mutual coupling under various movements. Furthermore, the multilayer interleaving is applied the circular coupler to enhance the self-coupling and minimize the cross coupling. The final experiment implements a series compensated system with the proposed coupler. The output current variation is less the 3.5% within the charging area.

A Circular-Arc-Type Magnetic Coupler with Strong Misalignment Tolerance for AUV Wireless Charging System

The wireless charging system (WCS) is widely employed to solve the problem of underwater charging of autonomous underwater vehicles (AUVs). However, the AUV is prone to misalignment caused by the tidal currents, which directly leads to fluctuations in transmission efficiency and output power. For this reason, a circular-arc-type (CA-type) magnetic coupler with strong misalignment tolerance was proposed in this article. Compared with the ring-type magnetic coupler, the proposed magnetic coupler had better magnetic field convergence and lower weight. Further, the effect of dimensional parameters on the CA-type magnetic coupler performance was analyzed by ANSYS Maxwell, with which the parameters of the magnetic coupler were optimized, and its coupling coefficient could finally reach 0.671. To analyze the influence of misalignment on the CA-type magnetic coupler, EE-type and UI-type magnetic cores are compared. Within the same range of rotation misalignment [−10°, 10°] and axial misalignment [−30, 30 mm], the CA-type magnetic core has stronger misalignment adaptability, and it can achieve a stable output power of 575 W and DC-DC efficiency of 92.51% when rotational misalignment occurs. A WCS experimental prototype is built based on one of the magnetic couplers and its experimental results verify the correctness of the theoretical analysis and simulation results.

Development of a New Backward Directional Coupler Based on Perforated Substrates

In this paper, two wideband 10 dB backward directional couplers based on artificial perforated substrates over the frequency range of 25-35 GHz and 32-38 GHz are developed. An analytical method is proposed to design the coupler geometrical parameters. The theoretical modeling is established based on the coupled version of the transmission line (TL) theory using the extended version of the ABCD matrix for four ports microwave network. It is shown that using the proposed method, all required parameters of the directional coupler are determined using the per-unit-length of the applied lines. The geometrical parameters of primary designed couplers are optimized using the particle swarm optimization (PSO) procedure to improve the performance of couplers. The designed couplers are also simulated using High Frequency Structure Simulator (HFSS) software. Moreover, sensitivity analysis is carried out to investigate the effect of fabrication imperfections of the proposed couplers. The obtained results show that the simulated results agree well with the theoretical ones and a low insertion loss (IL) with high return loss is obtained over a wide frequency range bandwidth.

High-Order Compensated Capacitive Power Transfer Systems With Misalignment Insensitive Resonance

A well-performed capacitive power transfer (CPT) system highly depends on its compensation to achieve load-independent (LI) output and zero phase angle (ZPA) operation. It is particularly meaningful to maintain these objectives under various misalignments. This paper is devoted to a general and comprehensive method to study and explore all the potential high-order compensations. The coupler parameter variation is evaluated under different types of misalignment, and misalignment-insensitive (MI) parameters are properly designed for MI resonance. A general and straightforward decomposition and synthesis method is then proposed to generate the high-order resonant tanks. With the help of inverse ABCD parameters, all tank candidates are further judged by their capability for LI output and ZPA operation. Finally, two example CPT systems are built to verify the LI output and ZPA operation under misalignment.

Optimum Design of Multi-Section Asymmetrical Transdirectional Couplers with Port Impedance Matching up to S Band Frequency

The method of least squares is developed for the optimum design of multi-section asymmetrical transdirectional (ATRD) couplers with arbitrary port impedance matching. Firstly, transmission matrix of a section of coupler is obtained, then the transmission matrix of whole multi-section coupler is determined, from which the scattering matrix of device is obtained. An error function is then constructed by scattering parameters. According to design specifications, error function depends on physical parameters of coupler (such as widths, spacings and lengths of transmission line sections and capacitor values), of which minimum point gives optimum values of it’s dimensions and capacitors. Optimum design is carried out for a specified frequency response and bandwidth. Error minimization is implemented by the combination of genetic algorithm (GA) and conjugate gradient method (CGM). The design is verified by full-wave simulation software, fabrication and measurement. Several 3 dB, 6 dB and 10 dB couplers are designed with different bandwidths and port impedances. Compared to the proposed design method, design of asymmetrical multi-section couplers by full-wave simulation softwares is by trial and error and at best random and almost impossible because of extremely high CPU time due to the large number of parameters of coupler geometrical structure.

Wide Bandwidth Silicon Nitride Strip-Loaded Grating Coupler on Lithium Niobate Thin Film

In this research, a vertical silicon nitride strip-loaded grating coupler on lithium niobate thin film was proposed, designed, and simulated. In order to improve the coupling efficiency and bandwidth, the parameters such as the SiO2 cladding layer thickness, grating period, duty cycle, fiber position, and fiber angle were optimized and analyzed. The alignment tolerances of the grating coupler parameters were also calculated. The maximum coupling efficiency and the −3 dB bandwidth were optimized to 33.5% and 113 nm, respectively. In addition, the grating coupler exhibited a high alignment tolerance.

Design of CPT System With Multiple Constant Output Voltage Pickups Using Inverse Hybrid Parameters of Capacitive Coupler

This article proposes a capacitive power transfer (CPT) system with multiple constant voltage (CV) pickups against variation of load resistance and the pickups moving in and out. First, a new equivalent circuit of the capacitive coupler is proposed by using the inverse hybrid parameters. Based on this model, an <i>LCLC</i>-compensated network is analyzed and designed to achieve a CV on the transmitting plates with a different number of pickups. Also, a simple series-compensated circuit is adopted at the secondary side to reduce the complexity of pickups and obtain a CV output when the load resistance changes. To verify the proposed modeling and design method, a 300-W experimental prototype of the <i>LCLC-LC</i> compensated CPT with two pickups is constructed. The experimental results show the output voltage of the system is almost unchanged and the inverter voltage and current remain in phase, when the load resistance varies and some of pickups are removed. The system efficiency remains above 85&#x0025; under different conditions.