Output Arms Research Articles

A spin-wave frequency demultiplexer based on YIG nanowaveguides intersecting at a small angle

We experimentally demonstrate a simple design for a spin-wave frequency demultiplexer based on submicrometer-width yttrium iron garnet waveguides intersecting at an angle of 30°. We show that, depending on the frequency, spin waves excited in the input arm of the device are predominantly directed to one of the two output arms. This spin-wave routing is characterized by a large extinction ratio of about 10. The frequency response of the demultiplexer can be efficiently controlled by changing the static magnetic field and the geometry of the device. Due to the small intersection angle and symmetry of the device, its operation does not require conversion between different types of spin-wave modes. This results in a high efficiency of the device and allows its facile integration into magnonic networks for complex signal processing and computing with spin waves.

Turbulence-resilient differential-phase-shift-keying free-space optical communications using automatic multi-mode optoelectronic mixing

Free-space-optical (FSO) communications can benefit from power-efficient modulation formats and detection methods. In general, differential-phase-shift-keying (DPSK) tends to be more optical-power efficient when detecting both output arms in the receiver as compared to intensity modulation. Unfortunately, turbulence can induce power coupling from a Gaussian mode to higher-order spatial modes, which can produce high power loss in the differential receiver. Here we demonstrate a 2.25-Gbit/s turbulence-resilient DPSK FSO link under emulated turbulence effects with a strength of 2ω0/r0∼5.5. The turbulence-induced modal coupling loss is automatically compensated by optoelectronic (O/E) mixing of many higher-order spatial modes. The experimental results, based on 200 random turbulence realization measurements, indicate that compared with a single-mode coherent receiver, the O/E multi-mode mixing can reduce the average turbulence-induced mixing loss by ∼14.6 dB.

Can buying weapons from your friends make you better off? Evidence from NATO

In this paper we analyse the effect of multilateral defence alliances and arms trade on economic growth of allies. Previous literature shows that military alliances may improve institutional development and efficiency in defence budget allocation, with consequent enhancement of economic performance. We postulate that importing advanced weapons from allies can bring about technology diffusion. This conjecture is developed theoretically assessing the effect of arms imports on domestic military technology and output. The model is tested for the countries that have a partnership relationship with the North Atlantic Treaty Organization for years 1990 to 2019. We confirm empirically the theoretical suggestion of military technology spillovers, namely, that imports of frontier technology arms from allies have positive effects on output and productivity through a diffusion of foreign knowledge. Our findings imply that policy makers should have in mind that foreign policy issues, security matters in this case, may interact with economic goals. • We analyse the effect of arms imports on economic growth of military allies. • Theoretical and empirical analysis is performed for NATO allies. • Output growth and arms imports from NATO allies are significantly positively related. • Advanced arms imports bring about an increase in technology via a spillover mechanism. • International cooperation in security can help improve economic performance.

High-Isolation Power Divider Based on Ridge Gap Waveguide for Broadband Millimeter-Wave Applications

In this article, a high-isolation power divider with ultrawideband characteristics for simultaneous operation in two adjacent bands is proposed. The power divider is developed based on a four-port coplanar Magic-T. The difference port of the Magic-T consists of a double-ridge gap waveguide (RGW) that supports quasi-TEM mode transmission, which provides the benefit of its broadband characteristics and allows for facilitated assembly. In addition, an inline microstrip line (MSL) containing a probe is inserted into the opposite side of the difference port to form the sum port. This basic configuration has actually achieved high isolation between the output arms and low return loss at each port, and however, its isolation bandwidth is limited by the narrowband matching of the sum port. To overcome this difficulty, a three-port microstrip T-junction is connected in series to the sum port of the Magic-T, resulting in a five-port 3-dB power divider with a wide isolation bandwidth. The process of considering this solution is analyzed and explained in detail in this article and the corresponding simulations and experimental verifications are performed. According to the obtained results, the proposed power divider has excellent overall performance, in particular low loss, ultrawideband, high isolation, and good amplitude/phase consistency.

Resistor-free and one-board-fits-all ratio adjustable power splitter for add-on RF shimming in high field MRI

Ratio adjustable power splitter (RAPS) circuits were recently proposed for add-on RF shimming. Previous RAPSs split the input RF signal with a Wilkinson splitter or 50-Ω-terminated hybrid coupler into two branches, delay these two signals with cable/microstrip line phase shifters, and recombine them with another hybrid coupler. They require resistors to provide high output isolation and a cable/microstrip line library to realize desired splitting ratios. Here we propose a novel resistor-free RAPS circuit in which the Wilkinson splitter/50-Ω-terminated hybrid is replaced with a resistor-free T-junction splitter. A novel sliding mechanism was employed to further combine the T-junction’s output arms with subsequent phase shifters and realize a one-board-fits-all design. The resistor-free RAPS was theoretically analyzed, simulated, and validated on workbench and MRI experiments. The resistor-free RAPS's splitting ratio has a tan/cot dependence on the phase/length difference between the T-junction output arms. The ratio can be continuously adjusted to any value by sliding the input arm without additional cable/microstrip libraries, largely saving time and effort when determining the best RF weights in practice. The fabricated resistor-free RAPS has a compact size, excellent input impedance matching, and a low insertion loss. Potential safety concerns caused by unwanted power dissipation on RF resistors are eliminated. The simulation and MRI experiments demonstrated that the resistor-free RAPS functions well on a widely-used Tx coil.

Do-it-yourself three-dimensional large core multimode fiber splitters through a consumer-grade 3D printer

We report the design, fabrication and characterization of 3D large core (1 mm) multimode fiber splitters using a low-cost stereolithography 3D printer. The results were accomplished for symmetrical 1 × 2 and 1 × 4 splitters, where the angle between the output arms was varied from 10 to 180°, showing good uniformity between the splitting ratios. Asymmetrical 1 × 2 splitters were also studied to achieve different splitting ratios. This was done by fixing one arm at a specific angle, while varying the other. Results were quite satisfactory, paving the way for simple and customizable manufacturing of passive optical elements.

T-Junction Loaded With Interdigital Capacitor for Differential Measurement of Permittivity

The microwave sensors have been successfully used for permittivity measurement. These sensors suffer from limited sensitivity and environmental effects. This paper presents a novel T-junction highly sensitive microwave sensor for permittivity measurement of low loss solid materials. The proposed sensor operation principle is based on downshifting the transmission zero of the outputs of T-junction with the coupling of the material under test (MUT). The sensing section consist of an interdigital capacitor (IDC) located in between the lines of the T-junction. IDC is directly connected to output arms of T-junction so that it could disturb the outputs strongly. Any change in electric field concentration in IDC directly is transmitted to the outputs and is translated as TZ change. Design steps including T-junction and IDC effects on outputs are presented in details. The sensor operation principle is described through an equivalent circuit model which is validated by simulation and experimental results. Two outputs of the proposed sensor show the same electrical performances which allow differential operation mode. Hence, cross sensitivity due to environmental factors can be tolerated by the sensor. Measurement results of the fabricated prototype shows 112 <i>MHz</i> frequency shift per unit permittivity change, and a normalized sensitivity of 3.9 %, which are larger than available similar sensors. The proposed sensor is implemented on a 22.22 &#x00D7; 18.76 &#x00D7; 1.6 <i>mm</i>³ printed circuit board.

A new type of non-thermal atmospheric pressure plasma source based on a waveguide bridge

A new type of microwave source of non-thermal atmospheric pressure plasmas, presented earlier by the authors, has both the characteristics of a dielectric barrier discharge (in terms of the configuration and low gas temperature) and an ability to form a “clean” plasma jet like a classical microwave plasma torch. However, the need to use a circulator leads to a significant increase in complexity, cost and weight of the installation as a whole. The basis of the presented plasma source is a three-decibel waveguide bridge with connection through a narrow wall. Both output arms of the bridge are loaded on identical short-circuited segments of waveguides. The discharge tube passes across the waveguides at a distance of a quarter of the wavelength from the short circuit. Since the output arms of the bridge are always loaded symmetrically, the generator’s power which is reflected from the short circuits or not be absorbed in the microwave discharge, enters the decoupled arm of the bridge that is connected to the matched load. Thus, the magnetron is protected from the reflected wave without the need for an expensive circulator, in any case.

High frequency power supply to improve operation stability of linear electron accelerator

The use of linear electron accelerators in medicine and industry is explained by the simplicity of the input and output of accelerated electrons and adjusting the energy and dose rate, as well as the high dose rate of bremsstrahlung. The purpose of this work is to increase the stability of their work. A standing wave accelerator containing a high-frequency generator, a phase shifter, a waveguide bridge, a high-frequency load, and an accelerating system of two accelerating sections is equipped with two waveguide tees. Their inputs are connected to the output arms of the waveguide bridge, and the first and second output arms of each tee are connected to the first and last accelerating cells of each section, respectively. In this system, due to the introduction of several elements that do not require large costs for manufacturing and tuning, a significantly greater frequency separation of the operating mode of oscillations from neighboring ones is ensured, or even a single-frequency excitation mode is implemented, which makes it possible to significantly increase the stability of the accelerator operation. This technique can be used to increase the stability of operation in the design and calculation of linear accelerators of electrons with a standing wave.

Features of the implementation of fixed phase shifters on coupled microstrip transmission lines with a stub

Fixed phase shifters with a phase-shifting channel based on coupled transmission lines of class II with a stub have a number of advantages in comparison with previously known structures for similar purposes. However, their practical implementation causes difficulties associated with the topological features of the structure, which, in turn, leads to a deterioration in frequency characteristics. In this regard, a numerical analysis of inhomogeneities in a class II structure with a stub and an assessment of their influence on the frequency characteristics of fixed phase shifters is required. In this work, circuitry and electrodynamic modeling of class II structure elements has been carried out, which showed that the greatest parasitic effect on the frequency characteristics of the phase shifter has a nonzero coupling coefficient of single transmission lines and an inhomogeneity localized at the junction of the short-circuited stub and the output arms of the associated transmission lines. A fixed phase shifter with a phase-shifting channel based on a smoothly stepped structure with a stub has been developed. The presented results of the study of fixed phase shifters based on microstrip coupled transmission lines of class II with a stub can be useful to scientific and technical workers engaged in the development of functional devices for the phase shift of microwave signals.

On Projective Connection of Optically Conjugate Points of Static Mass Analyzers

The Barber rule, known in the theory of sector static mass analyzers and connecting geometrically the axial point of an object and its electron-optical image (Gaussian points) in the case of a uniform field of a magnetic sector with a normal incidence, is generalized to the case of arbitrary geometries and fields of magnetic and electrostatic sectors. It is proved that the Gaussian points of the optical axis of the mass analyzer are connected by a bipolar projection through two points – the poles of this projection, located on the straight lines passing through the optical foci of the mass analyzer parallel to the input and output arms of the optical axis. The distances of these poles from the foci adjacent to them are subject to the well-known optical invariant of Newton.

Quadrature phase detection based on an extrinsic Fabry-Pérot interferometer for vibration measurement.

A novel vibration measurement system based on a fiber-optic extrinsic Fabry-Pérot interferometer is established. Two quadrature interferometry signals are obtained in accordance with the 90° phase shift between two output arms of a 2×2 fiber coupler. This outcome drastically simplifies the processing of collected data because only a single arctangent operation is needed to calculate the wrapped phase. Repetitive test results show that the relative micro-vibration reconstruction error of this method is less than 0.12%. This structure simplifies the extrinsic Fabry-Pérot signal demodulation process, which has guiding significance for the online measurement of high-precision physical quantities.

A Novel Microstrip Line Balun With Transparent Port Impedance and Flexible Open Arm Structure

In this letter, a novel microstrip line balun with transparent port impedance and unconnected flexible output arms is presented. The proposed balun is designed from a symmetric four-port device with an open end at its isolation port. To achieve balun function, a shunt stub is attached between the unbalanced port and the virtual open-ended port to generate a transmission zero under the even-mode circuit. Its odd-mode circuit is treated as an impedance transformer, where the transformer is independent of the terminal impedance. In addition, the proposed balun has flexible open arm branches and does not require a closed loop structure, which provides design flexibility to integrate with other devices compared to conventional closed-loop branch line baluns. The theoretical design equations are derived first to prove the design concept. Then, two prototypes are designed with 35 $\Omega $ system impedance and loaded with 50 and 75 $\Omega $ port impedance, and the measured results match well with the simulation, which further validates the proposed design theory.

Full Band Compact Power Arm Subsystem With High Directive Sample

An output arm is the first subsystem in the microwave components chain connected immediately after the power amplifier. These arms are responsible for transferring the signal from the output port of the power amplifier to the standard line of the system. The second objective is to obtain directive samples for both forward and backward signals. The typical design process for such a subsystem is carried out through the design of separate components, independently. This limits the achievable performance of the entire system and introduces excessive losses at intermediate flanges. In this work, we present a novel approach to design such a subsystem using a global optimization procedure. Specifically, we address both compactness and full-band operation of output arms deployed in radar applications. Analysis and design of each component in the proposed subsystem are illustrated. The presented subsystem achieves a deep matching level of 19 dB within an overall length below $2\lambda _{g}$ . Moreover, the directive sample obtained through the presented design has an ultra-flat response of 20 dB ± 0.5 dB over the entire band of operation, while the directivity of the samples exceeds 18 dB. The measured results of the fabricated prototype have an excellent agreement with the simulations.

Auto-balancing and robust interferometer designs for polarization entangled photon sources

A new implementation of a Mach-Zehnder interferometer is presented. Aimed at facilitating coherent optical wavelength conversion, the interferometer utilizes a novel double displacement technique that eliminates dispersion induced phase discrepancies between its input and output arms. To demonstrate the design, the interferometer was incorporated into a source of polarization entangled photon pairs. The source produced on average 2-3 million photon pairs per second per mW of pump power, the pairs emitted being maximally entangled in the polarization degree of freedom with a fidelity of ≥98%_. The new interferometer implementation is simple and robust and promises to become a design benchmark for polarization entangled photon sources.

Grating-Coupled Silicon-on-Sapphire Polarization Rotator Operating at Mid-Infrared Wavelengths

We provide an experimental demonstration of mid-infrared polarization rotators built on a silicon-on-sapphire platform at the mid-infrared wavelength of $4.55~\mu \text{m}$ to enable integration of quantum cascade lasers (QCLs) and detectors with slotted photonic crystal waveguide (PCW) gas sensors for on-chip optical spectroscopy applications. The polarization rotators are essential to convert the preferentially transverse magnetic (TM) polarized light from a QCL to transverse electric (TE) polarization to interface with the preferential TE-guiding slotted PCW sensors. The polarization rotator consists of an adiabatic-tapered mode converter followed by a phase shifter and a multimode interferometer that effectively transfers energy from an input fundamental TM00 polarization to a first-order TE10 polarization that is then converted to the fundamental TE00 mode. Polarization-selective sub-wavelength grating couplers are designed and fabricated to effectively couple TE or TM polarizations at the designed wavelengths into and out of the polarization rotator device for efficient device characterization. TM00–TE10 conversion efficiency of 100% is simulated. Fabrication tolerances in the phase shifter result in an experimental 80:20 splitting ratio of the measured output TE00-polarized light between two output arms.

Long Range Multilayer Hybrid Plasmonic Waveguide Components and Integrated Circuit

In this work, CMOS compatible hybrid insulator metal insulator (HIMI) planar plasmonic waveguide based components such as, racetrack ring resonator, y-splitter, coupler and dual parabolic profile nano antenna have been proposed and investigated at 1.55 μm operating wavelength for the first time. The proposed components are analyzed at various parametric variations using CST microwave studio. The proposed racetrack ring resonator offers 153.88 nm free spectral range, 0.3232 nm FWHM and 46.57 dB extinction ratio at 0.40 μm radius and 0.49 μm separation length. Y-splitter divides equal power of 46.85% in both output arms and coupler couples till 86.5% power in coupled arm. The dual parabolic profile nano antenna offers a gain, bandwidth and efficiency of 7.99 dB, 203 THz and 84.56 % respectively. Using all the components, HIMI plasmonic integrated circuits have also been designed and investigated for on chip applications. Proposed components work very efficiently in chip scale integrated circuit. This investigation provides groundwork for future chip scale applications.

Electrostatic beam splitter for polar molecules

An electrostatic beam splitter composed of three charged poles for polar molecules in weak-field-seeking states is proposed. First, the schematic diagram is given. Then we calculate the spatial distribution of the electrical field using the finite element software. We simulate the dynamic process of the loading and splitting polar molecules using the classical Monte Carlo method. We investigate the influences of the longitudinal velocity of the incident molecular beam and the voltages on the performance of our beam splitter. In order to alter the splitting ratio of the molecular beam conveniently, we cut off the two output arms of beam splitter at a certain position. Then we study the influences of the voltages and cutting positions on the splitting ratio. At last, we discuss two methods of keeping the height of guiding center nearly unchanged.

Femtosecond laser inscribed cladding waveguide structures in LiNbO3 crystal for beam splitters

Depressed cladding, buried waveguides, and beam splitters in z cut LiNbO3 crystals were fabricated by femtosecond laser inscription. Straightforward cladding waveguides were optimized by varying the laser writing conditions. Minimum propagation losses of 0.74 dB / cm at 1.05-μm wavelength were obtained. Two-dimensional 1 × 2 and three-dimensional 1 × 4 beam splitters were realized. 1 × 2 Y-splitters with circular cladding geometry are fabricated with 60-μm diameter input ends, corresponding to two 30-μm diameter output ends, respectively. The full branching angle between the two output arms are changing from 0.5 deg to 2.4 deg. The splitters were characterized both experimentally and numerically, showing excellent properties including symmetrical output ends and equalized splitting ratio. 1 × 4 splitters with square cladding geometry reached splitting ratios of 26 ∶ 26 ∶ 22 ∶ 26. The micro-Raman spectra indicate the slight microstructural lattice changes in the track and core region.

Design, modeling and control of a novel compact, energy-efficient, and rotational serial variable stiffness actuator (SVSA-II)

This paper presents a new compact, rotational serial variable stiffness actuator (SVSA-II) based on a symmetrical adjustable pivot lever mechanism that generates elastic torque and permits output stiffness adjustment. By introducing a symmetrical stiffness transmission mechanism consisting of two sets of lever arm mechanisms mounted on a rotational output shaft, the internal friction and energy loss can be reduced to improve the energy efficiency. The new mechanism permits stiffness adjustment from zero to infinity without any structure constraints. The displacement of the springs occurs in the direction vertical to the output arms based on the spring frame. This modification improves the conversion efficiency of stored energy to output toque. The symmetrical Archimedean Spiral cam introduced here reduces the complexity of stiffness control using linear transmission. Control experiments are performed to evaluate the physical performance of the SVSA-II. Our results demonstrate that the SVSA-II with a proportional derivative (PD) feedback and feedforward controller exhibits a good response and high accuracy for position regulation, stiffness regulation and tracking tasks. Moreover, low damping coefficients and relatively high energy storage efficiencies are observed under different stiffness conditions in oscillatory damping experiments.