Dependence Of Coupling Coefficient Research Articles

Dynamical behavior of two locally coupled asymmetric RF-SQUIDs

An asymmetric system consisting of two coupled radio frequency superconducting quantum interference devices (RF-SQUIDs) with general geometry as nonlinear macroscopic system with mutual inductance under the influence of a time-dependent external field has been investigated numerically. Due to the importance of mutual induction in the construction of such nonlinear asymmetric systems, the dependence of coupling coefficient on the frequency changes, the primary and secondary resonance amplitudes and also the anti-resonances in both squids have been investigated. By changing the geometry of the arrangement of squids, the dynamic behavior parameters of the system have been studied. The eigenvalues of this system have been found and by changing frequency, the stable and unstable states have been studied.

Nonlinear dynamics and synchronization of saline oscillator’s model

The Okamura model equation of saline oscillator is refined into a non-autonomous ordinary differential equation whose coefficients are related to physical parameters of the system. The dependence of the oscillatory period and amplitude on remarkable physical parameters are computed and compared to experimental results in order to test the model. We also model globally coupled saline oscillators and bring out the dependence of coupling coefficients on physical parameters of the system. We then study the synchronization behaviors of coupled saline oscillators by the mean of numerical simulations carried out on the model equations. These simulations agree with previously reported experimental results.

Seismoelectric measurements in a porous quartz‐sand sample with anisotropic permeability

ABSTRACTSeismoelectric coupling coefficients are difficult to predict theoretically because they depend on a large numbers of rock properties, including porosity, permeability, tortuosity, etc. The dependence of the coupling coefficient on rock properties such as permeability requires experimental data. In this study, we carry out a set of laboratory measurements to determine the dependence of seismoelectric coupling coefficient on permeability. We use both an artificial porous “sandstone” sample, with cracks, built using quartz‐sand and Berea sandstone samples. The artificial sample is a cube with 39% porosity. Its permeability levels are anisotropic: 14.7 D, 13.8 D, and 8.3 D in the x‐, y‐, and z‐directions, respectively. Seismoelectric measurements are performed in a water tank in the frequency range of 20 kHz–90 kHz. A piezoelectric P‐wave source is used to generate an acoustic wave that propagates through the sample from the three different (x, y, and z) directions. The amplitudes of the seismoelectric signal induced by the acoustic waves vary with the direction. The highest signal is in the direction of the highest permeability, and the lowest signal is in the direction of the lowest permeability. Since the porosity of the sample is constant, the results directly show the dependence of seismoelectric coefficients on permeability. Seismoelectric measurements with natural rocks are performed using Berea sandstone 500 and 100 samples. Because the Berea samples are nearly isotropic in permeability, the amplitudes of the seismoelectric signals induced in the different directions are the same within the measurement error. Because the permeability of Berea 500 is higher than that of Berea 100, the amplitude of the seismoelectric signals induced in Berea 500 is higher than those in Berea 100. To determine the relative contributions of porosity and permeability on seismoelectric conversion, we carried out an analysis, using Pride (1994) formulation and Kozeny–Carman relationship; the normalized amplitudes of seismoelectric coupling coefficients in three directions are calculated and compared with the experimental results. The results show that the seismoelectric conversion is related to permeability in the frequency range of measurements. This is an encouraging result since it opens the possibility of determining the permeability of a formation from seismoelectric measurements.

Interplay between relaxation of nonlinear response and coupling coefficient dispersion in the instability spectra of dual core optical fiber

The modulational instability of a dual core optical fiber under the combined effect of coupling coefficient dispersion (CCD) and relaxation of nonlinear response is presented. The effect of wavelength dependence of coupling coefficient is effectively included in the pair of generalized linearly coupled nonlinear Schrödinger equation (CNLSE). In order to account for the finite response time, a time dependent nonlinear response is incorporated in the system of CNLSE using the Debye relaxation model. The results from the linear stability analysis show that in anomalous dispersion regime for any finite relaxation time, the nonlinearity becomes complex and there exist two unstable modes. In the normal dispersion regime, a single unstable band at higher detuning frequency is observed which is identified as the Raman band. In symmetric case the CCD is found to be immaterial, whereas in asymmetric case the CCD is found to be crucial and brings new spectral bands. A critical value of CCD is predicted where the dynamics evolve dramatically in different manners. Thus in this paper, the MI dynamics of a dual core optical fiber is fully explored and the interplay between CCD and relaxation is clearly highlighted.

Coupling coefficient calculation for GaSb-based quantum well distributed feedback lasers with laterally coupled gratings

We calculated the coupling coefficient of different types of laterally coupled distributed feedback (LC-DFB) structures with coupled-wave theory and the two-dimensional semivectorial finite difference method. Effects neglected in previous studies such as other partial waves, the ohmic contact and metal contact layers are taken into account in this calculation. The LC-DFB structure with metal gratings is especially studied due to its advantage over index-coupled structures. The dependence of coupling coefficient on structure parameters is theoretically calculated such as grating order, ridge width, thickness of the residual cladding layer, grating depth and lateral proximity of gratings to the ridge waveguide. A complex-coupled GaSb-based 2 µm LC-DFB structure is optimized to achieve a high coupling coefficient of 14.5 cm−1.

Coupling coefficient of a composite dielectric resonator with rectangular waveguide

Dependence of coupling coefficient between split dielectric resonator and rectangular waveguide on composed dielectric resonator and waveguide geometrical sizes and material permittivity was established. The coupling coefficient was estimated in terms of S parameter approximation calculated by finite element method. Improvement of dielectric resonator coupling with rectangular waveguide more than by 100% is proposed. Such effect was achieved by insertion of dielectric discontinuity perpendicular to DR’s electrical field. It results in increasing of attenuation in band-stop filters and decreasing of insertion loss in band-pass filters

Classical analogues to quantum nonlinear coherent states in photonic lattices

We show that light evolution occurring in waveguide arrays with a particular n-functional square root dependence of coupling coefficients can be used to produce classical analogues of nonlinear quantum coherent states. Using operator algebras we obtain closed-form expressions describing the optical field dynamics in such structures. In addition, by numerically monitoring the Mandel's parameter, we obtain the conditions necessary to generate sub-Poissonian and super-Poissonian classical intensity distributions in the proposed photonic lattices.

Dependence of coupling coefficient and lasing wavelength on injection current in pure gain-coupled distributed feedback semiconductor lasers

A theoretical analysis of purely gain-coupled distributed feedback lasers (PGC-DFB) with antireflection facets is given. The effects of longitudinal non-uniformity of photon and carrier density above a threshold circumstance are considered. In addition, the influence of carrier-induced refractive index change on the coupling coefficient of the PGC-DFB structure is assumed. It is shown that the coupling coefficient in this structure varies with injected current and it gets a real part or an index coupled term. As a result the normalized coupling coefficient, κL, becomes a complex number. So, above the threshold condition, the PGC-DFB laser operates like a complex coupled one. Variation of the oscillation wavelength and the threshold gain of the PGC-DFB laser in terms of current is analyzed too. Numerical analysis shows that this structure has wavelength tunability with respect to current. The theoretical model is based on the self-consistent solution of coupled wave equations and the carrier rate equation by the transfer matrix method.

Coupling coefficient dependence on oscillation frequency stability of self-pulsating DFB laser diodes

Grating coupling strength effects in self-pulsating distributed feedback lasers were investigated. Choosing the coupling coefficient appropriately, improvements in the timing jitter as well as the injection locking sensitivity were observed experimentally. The results are attributed to a co-ordination of optical feedback strengths between dual lasing modes.

Modal interference in dual-core photonic crystal fibers

The modal characteristics of dual-core photonic crystal fibers(PCFs) are analyzed by a full vector supercell lattice overlapping model. The fundamental and second-order modes of dual-core PCFs consist of a pair of even and odd modes with different polarization. The parity properties of the modal electric field for the fundamental and second-order modes are discussed. Based on the analysis of parity of the modal electric fields, we investigated the vector modal interference in dual-core PCFs.It is the interference between two same polarized modes that conributes to the inter-core coupling of power. It is shown that the optical power will oscillate from one core to the other and the phase difference between both cores is about π/2. The dependence of coupling coefficients for different polarization on wavelength is discussed.

Chaotic synchronization in lattice of partial-state coupled Lorenz equations

In this paper, we study chaotic synchronization in lattices of coupled Lorenz equations with Neumann or periodic boundary condition. Three different coupling configurations in the single x i -, y i - or z i -component are considered. Synchronization is affected by coupling rules. We prove that synchronization occurs for either x i - or y i -component coupling provided the coupling coefficient is sufficiently large. Moreover, we determine the dependence of coupling coefficients on the lattice size. For the case of the z i -component coupling, we demonstrate by numerical experience that the synchronization cannot occur.

Magnetomechanical coupling and elastic moduli of polymer-bonded Terfenol composites

The dependence of coupling coefficient (k) and elastic moduli (EH and EB) on particle size and volume fraction of Terfenol powder in polymer-bonded composites has been investigated. Materials were prepared with powder in five size ranges between 106 and 710 μm and in three volume fractions (VF). The moduli show a ΔE effect, which is negative for small bias fields and positive for larger fields. EH is found to be independent of particle size and to vary with VF in agreement with model predictions. The maximum value of k, for each sample, is found to be independent of both particle size and VF and a simple model is presented which predicts this behavior and indicates that the low values of kmax arise mainly from the low modulus of the epoxy binder.

Evaluation of Coupling Coefficients for Laterally-Coupled Distributed Feedback Lasers

Dependence of coupling coefficient, κ, on laterally-coupled distributed feedback (LC-DFB) laser structure is investigated. In LC-DFB lasers, gratings are fabricated on and around the ridge after ridge-waveguide formation and, thus, neither epitaxial regrowth nor growth on corrugated substrates is required. For κ calculation, coupled-mode theory is used with the two-dimensional field intensity calculated using the imaginary-distance beam propagation method. Comparisons are made for LC-DFB lasers with different layer, ridge and grating structures and parameters that affect κ are identified. In addition, it is shown that LC-DFB structure is less sensitive to processing variations and, thus, more manufacturable than a conventional buried heterostructure DFB structure.

Plasma-target coupling in the case of TEA-CO 2 laser produced breakdown in front of a solid target

New experimental results concerning the coupling coefficient dependence on geometric conditions, target nature, ambient gas pressure and nature in the case of solid targets irradiation in controlled ambient atmospheres are reported. The data are analysed from the point of view of the relative weight and interference of the proposed mechanisms for energy transfer.

Mutual coupling coefficients in collector arrays on circular cylindrical concave surfaces

An analysis is presented of mutual coupling in collector arrays on a concave side of a large conducting circular cylindrical surface. The collector elements are uniformly spaced narrow axial slits which are parallel-plate-guide-fed in the TEM mode. Each element is equipped with a matching network appropriate to broadside scan in the corresponding planar slit array. The properties of coupling coefficients are studied numerically. It is shown that for spacing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</tex> less than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda/2</tex> , past a certain curvature dependent neighborhood of the excited element, the rate of decay of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -plane coupling coefficients is considerably slower than in a planar array with the same elements and spacing. The slower decay of coupling coefficients should be considered in evaluation of the efficiency of collector arrays on concave surfaces. For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda &gt; d &gt; \lambda/2</tex> the dependence of coupling coefficients on the distance exhibits considerable fluctuations which are attributed to grating-lobe formation. It is also shown that the collector element mismatch may be enhanced by the collector cavity resonances, so that the criteria for admissible voltage standing-wave ratio (VSWR) level of collector elements may be more stringent than in planar arrays.

Coupled parallel rectangular dielectric waveguides

The method of adiabatic invariance of action applied to electromagnetic resonators is used in the analysis of coupling between rectangular dielectric rods. The field values used in the analysis are obtained by a point-matching technique. The results are supported by experiments. For a certain configuration, an almost linear dependence of coupling coefficient on frequency is found over a wide range of frequencies.