Frequency splitting effect of degenerate modes in ferrite resonators

The splitting of magneto-dielectric modes frequency in disk ferrite resonators in a magnetic field is considered.Asimplified formula is obtained for estimation of the splitting magnitude. Theoretical and experimental results of the frequency splitting effect in magneto-dielectric modes in the millimeter wave range are compared. The use of the splitting of the magneto-dielectric modes frequencies as an alternative to ferromagnetic resonance in devices with magnetic frequency tuning is suggested, with values of the magnetization fields being an order of magnitude lower than for ferromagnetic resonance. The features of the splitting modes effect in different ferrite classes are investigated and it is shown that it occurs in both microwave and optical ranges. The estimated magnitude of the mode frequency splitting in the iron-yttrium garnet (YIG) transparency window can reach 9 GHz, which is comparable to the 5 GHz splitting in the millimeter range. The frequency ranges where frequency splitting effect is of practical interest are discussed. In particular, the effect in barium hexaferrite can be used both in post-resonance and pre-resonance regions, which is almost impossible for ferrogarnates and ferrospinels.     

Coupling characteristics of eccentric arranged dielectric disk andring

An analysis is presented for a novel coupling configuration in which a circular dielectric disk and ring are arranged eccentrically. Whispering gallery (WG) mode coupling characteristics between the dielectric disk and ring are investigated. In this paper, a coupled-mode equation based on the Lorentz's reciprocity theorem is utilized. Distributed coupling coefficients and electric field distributions around the coupling region are obtained numerically through solving the coupled-mode equation. The theory described in this paper is confirmed by comparing measured electric field distributions with calculated ones. Electromagnetic powers flowed along the disk are also calculated. It is shown that coupling quantity of the eccentric configuration would be easily controlled by changing a radius of the disk or ring. The results obtained here will be used to design a WG mode coupled resonator for millimeter wave integrated circuits     

Double Fano resonances in disk-nonconcentric ring plasmonic nanostructures

The plasmonic properties of gold nanostructures composed of a disk outside a nonconcentric ring are numerically studied by the finite difference time domain(FDTD) method. Simulated results show that two Fano resonances are formed as a result of the coupling of the octupolar and quadrupolar modes of the ring with the dipolar mode of the disk. The reduction in structural symmetry causes a red shift of the Fano resonances and distinct changes in spectral lineshape by offsetting the center of the in...     

Fabrication and test of an electromagnetic vibrating ring gyroscope based on SOI wafer

Mode matching is tile key to improve the performance of micro-Inachined vibrating ring gyroscopes. Mass and stiffness asymmetries can lend to normal modes badly mismatch for gyroscopes fabricated by single-crystal silicon. The mismatch of the normal nodes results in large normal mode frequency split and degraded sensitivity. To address this issue, a Silicon-On-Insulator （SOI） wafer is used to fabricate the sensor chips. Meanwhile, a compensate disk and the backside coated negative photo resist （AZ303） is employed to weaken the Lag and Footing effect during the Deep Reactive Ion Etching （DRIE） process. Test results reveal that frequency split between the normal modes is of less than 10 Hz before the following electronic tuning. Thus, the mode matching of the electromagnetic vibrating ring gyroscope is probable to be realized.     

Resonant ring fiber filters

We have studied structures where a concentric ring with an index higher than that of the cladding index is added to a conventional fiber core. The structure supports at least one additional symmetric mode with substantial power in the ring, besides the normal mode in the core. Within certain designed parameter regimes, the propagation constants of the lowest two symmetric modes cross at a certain wavelength. This is equivalent to saying that the LP01 mode can change from having more power in core to having more power in ring at a certain wavelength or vice versa. At this resonance, each of the two modes has substantial power in the core and the ring. This resonant nature of the structure creates a strong wavelength dependent mode field for LP01 and LP02 modes near the resonance wavelength. Filters based on this principle are demonstrated for the first time     

Chaotic dynamics of mode competition in a vertical-cavity surfaceemitting laser diode under DC excitation

We discuss the dynamics of transverse mode competition in an etched air-post vertical-cavity laser diode under dc excitation using an annular ring contact as a spatial filter. Distinct regions of operation are found for various ranges of fixed bias currents. At 1.5 times threshold, the device enters a region which exhibits chaotic fluctuations between the fundamental and a higher order lasing mode. The dynamics of these fluctuations are studied using the method of delays, and a calculation of the power spectrum and the correlation dimension are reported. It is found that the dynamics of the chaotic fluctuations have a correlation dimension of approximately 2.8. The results are indicative of a low-dimensional strange attractor underlying the modal competition noise     

Composite-Junction Circulators Using Ferrite Disks and Dielectric Rings

Since most junctions do not use the full available magnetic splitting of the ferrite material, it is possible to replace part of it by a dielectric. The theoretical and experimental development of such composite stripline circulators using ferrite disks surrounded by dielectric rings is given in this paper. Theoretical calculations and experimental results on the circulation frequency, gyrator admittance, and split frequencies of such circulators are included. The case of a partially magnetized ferrite disk on a ferrite substrate is treated separately. The suscteptance slope parameter of this circulator geometry is also derived and measured. The results obtained in this paper show to what extent the ferrite disk behaves as a dielectric at the edge of the disk. The geometry leads to considerable saving in ferrite material, which is particularly important in UHF circulators. The experimental results are in good agreement with the theory.     

A method for investigating a class of inhomogeneous striplinecirculators

Broad-band stripline circulators are studied by means of a mixed numerical technique which employs both boundary integral and segmentation methods; this technique allows the analysis of planar circuits where the substrate is constituted by several regions with arbitrary shapes and different electrical properties. It is known that tracking circulators require matching structures because they present a low-gyrator impedance (real and almost constant in an octave frequency band). The matching structures (generally tapers or multisection's transmission line transformers) must be realized on a reciprocal substrate. The overall device (circular disk on ferrite substrate and matching structure on dielectric substrate) constitutes a planar circuit with an inhomogeneous medium. The method of study presented here allows the determination of the overall impedance matrix of the planar circuit constituted by the nonreciprocal disk with sections of striplines connected to each port; in this way, the discontinuities between reciprocal and nonreciprocal medium are included in characterization of the overall device. Moreover the accuracy of the representation is increased, In fact, the coupling ports of the overall device may be located at a suitable distance from the disk boundary where higher-order modes excited by the discontinuities have been sufficiently attenuated and only the TEM mode is present on the striplines (which is the only one considered in the design of the matching structures)     

辐射压力诱导强耦合光机械腔中的简正模式分裂和冷却

在解析边带机制下用量子郞之万方程研究一种由辐射压力与驱动Fabry-Perot光学腔相耦合而产生的光机械动力学行为。随着输入激光功率的增加,振子的涨落光谱呈现简正模式分裂的现象,并且结果和实验相符合。也推导了有效机械阻尼和共振频移。红移边带导致了机械模的冷却,蓝移边带引起了机械模的放大。此外,引入一种近似机制来研究振子的冷却。由于简正模式分裂和基态冷却都要求在解析边带机制下,这就需要考虑简正模式分裂是否会影响到振子的冷却。同时也讨论了操控基态冷却的关键因素。     

Capacitance characterization method for thick-conductor multipleplanar ring structures on multiple substrate layers

A capacitance characterization method for thick-conductor multiple planar ring structures on multiple substrate layers has been made by extending the rectangular boundary division method. The region to be considered in the analysis is divided into subregions of thick-wall cylindrical tubes in each of which Laplace's equation is solved by the method of the separation of variables. A special application scheme of the boundary conditions is devised to decrease the number of necessary equations. Numerical results are shown for circular disk and planar ring structures in comparison with other available data     

Wannier-stark effect in Ge/Si quantum dot superlattices

Deep level transient spectroscopy (DLTS) measurements were performed to study electron emission from quantum states in a 20-layer Ge quantum-dot superlattice (QDSL) in a Ge/Si p-n heterostructure. It was established that the changes in the DLTS spectra depend heavily on the magnitude of the applied reverse bias U _r . Three regions of the reverse bias U _r were identified, corresponding to the manifestation of the three modes of the Wannier-Stark effect: Wannier-Stark ladder mode, Wannier-Stark localization, and nonresonant Zener tunneling mode. Furthermore, it was found that the appearance of DLTS peaks for all three modes is associated with electron emission from deep-level defects via Wannier-Stark localized states arising as a result of the splitting of the electron miniband of the Ge/Si QDSL.     

Neural network fitting and prediction of polarisability tensors for aromatic hydrocarbons

A standard back-propagation neural network is used to correct input semi-empirical molecular orbital calculations of polarisability tensors to fit experimental data for aromatic hydrocarbons. The method readily yields the correct component normal to the molecular plane but is restricted by a small training set. The network is also used to predict polarisability components for structures input as the pattern of rings fused to a central benzene ring. Semi-quantitative predictions are obtained depending on the size and method of presentation of the training set.     

大位移交叉环形电极压电驱动器结构优化

设计一种交叉环形电极与压电圆盘驱动器相结合的交叉环形电极（CREs）压电圆盘驱动器,利用分析软件ABAQUS进行静力学分析,着重研究CREs型压电圆盘驱动器电极结构几何尺寸以及驱动器厚度对驱动器径向驱动性能的影响。研究结果表明,减小电极中心距与驱动器厚度,有利于提高驱动器的驱动性能;加载相同电压,CREs型压电圆盘驱动器的径向夹持应力能达到普通型的2.1倍,径向自由应变能达到普通型的3.4倍。CREs型压电圆盘驱动器性能研究为CREs型压电圆盘驱动器的设计制造提供了一定的理论依据。     

Thermal spreading resistance of ring-geometry diodes

Mesa avalanche diodes shaped in ring structures have lower thermal spreading resistances than conventional disk mesa diodes of equal junction area. A simple analog electrolytic tank was built to measure the spreading resistance of ring geometries, A normalized curve was obtained which allows the determination of thermal spreading resistance for any ring structure.     

Surface measurements of disk antennas

Measurements of waves of normal electric field and tangential magnetic field over the surfaces of disk antennas agree with calculations consisting of addition of Young-Huygens wavelets from elements of edge arriving at any point on the surface of the disk.     

The Transmission of TE/sub 01/ Wave in Helix Waveguides

Relations are investigated between the transmission characteristics of a helix waveguide and its surface impedance in regions where any simple approximate formulas are not available because of the magnitude of the surface impedance. The numericaf calculations show that, for any given value of the surface impedance and the angular mode index, there exist an infinite number of different modes which are distinguishable from each other by different values of the radial propagation content. Selecting a mode with minimum attenuation for each given surface impedance, we can draw the equiattenuation lines, connecting these points of equal attenuation on the complex surface impedance plane. At some point on the complex surface impedance plane, a maximum value of the minimum attenuation is found. For the TM/sub 0/ mode supported by a helix waveguide 50 mm in diameter, used at a frequency of 50 kmc, this minimax value of the attenuation constant is about 8 neper per meter, and the corresponding value of the surface impedance is about 57.6-j28.8 ohms. The attenuation constants of all the TM/sub 0/ modes corresponding to this optimum value of the surface impedance cannot be smaller than this minimax value. The same kind of calculations are also performed for the two lowest hybrid modes. Physical structures giving the best value of the surface impedance are also suggested.     

Analysis of the microstrip disk antenna element

The circular microstrip antenna element is formed by a radiating disk closely spaced above a ground plane. It is modeled as a cylindrical cavity with magnetic walls which can be resonant in the transverse magnetic (TM) modes. The far fields and the radiation conductances for different mode structures have been calculated assuming a magnetic line current flowing along the perimeter of the disk. The directivity of a disk antenna excited in the dominant mode is between 4.8 dB and 9.9 dB, depending on the size. Losses, due to imperfect supporting dielectrics and to the finite conductivity of the conductors, have been derived by means of a perturbation technique. Graphs are given for design purposes showing the input impedance, theQfactor, and the radiation efficiency at resonance for different modes and thicknesses. The air-filled microstrip antenna has the highest efficiency and the broadest bandwidth at a given resonant frequency.     

Analysis of propagation characteristics of whispering gallery modes in a dielectric disk or a curved rectangular dielectric waveguide

The finite-element method is applied to the analysis of whispering gallery modes in curved optical waveguides. Numerical examples for whispering gallery modes in a dielectric disk with rough boundaries are given. It is demonstrated that the whispering gallery modes and the normal guided modes in a curved rectangular dielectric waveguide are analyzed consistently with this approach, and that the normal guided mode approaches the whispering gallery mode with the increase of waveguide width. The minimum width of the rectangular waveguide needed to support a whispering gallery mode is evaluated.<>     

Charge transfer in thin films of donor–acceptor complexes studied by infrared spectroscopy

The degree of charge transfer in thin films of organic charge transfer (CT)-complexes, which are deposited via thermal evaporation, is examined via infrared-spectroscopy. We demonstrate a linear relationship between the shift in the excitation energy of the CN-stretching mode of CT-complexes with the acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) and the charge transfer. The measured correlation corresponds very well with DFT calculations. For Na-TCNQ we observe a splitting in the peak of the CN-stretching mode, which can be explained by the coupling of two modes and was confirmed by the calculations. In CT-complexes with partial charge transfer the appearance of an electronic excitation is demonstrated.