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The simulation of wires is essential for the numerical modelling of many problems, such as those related to electromagnetic compatibility (EMC). The Letter identifies the cause of errors occurring when modelling wires using the transmission-line modelling (TLM) method. A new approach is proposed which is shown to give good agreement between simulated and experimental results.

At high frequencies, the current distribution across a circular wire is modified by the skin effect, causing the greatest current density to be near the surface of the wire. One common method of calculating the wire resistance inoles determining complex Bessel func- tions, the solution of which is prone to approximations as the skin depth becomes less than about one tenth the wire radius. An alternatie method of determining this resistance is presented which is significantly simpler than the Bessel function approach, easier toisualize, and not reliant on approximations when determining the solution. This approach is based on determining the width of an annulus which carriers the equialent current to the full wire. Results are presented which confirm the accuracy of the equialent annulus method. Q 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 84)87, 1998.

The direct modification of materials by femtosecond (fs) laser pulses enables fabrication of 3D compact photonic devices, which are potentially cheap and allow for dense integration. In the writing of well-defined structures by such means non-linear processes are essential. Multi-photon absorption is an effect that initiates plasma formation in illuminated region and subsequent variation of its optical properties. Due to the non-linear character of absorption, sub-wavelength-scale (in particular, nano-scale) structures can be fabricated.

We present a detailed and rigorous analysis of finite-size coupled-cavity optical waveguides (CCWs) - practical elements with tunable characteristics that enable guiding, routing, slowing and storing light. We discuss recent advances in design, fabrication, and applications of such structures and study mode coupling and guiding mechanisms in straight and curved CCW sections composed of optical cavities with sizes above, on and below optical wavelength. Possible ways to reduce or compensate radiation and absorption losses are proposed. These include optimal tuning of the waveguide bend geometry and exploring new classes of hybrid photonic-plasmonic mesoscale guiding structures. Application of plasmonic nanocavity arrays as optical-microcavity-coupled end-structures for focusing and channelling optical energy to single atoms, molecules, and nano-emitters is also discussed.

We develop time domain models of selenide-chalcogenide glass fiber based MIR spontaneous emission sources. The modeling parameters used are derived from experimentally obtained data. The models are based on the rate equations’ approach to simulate the distribution of ions between the relevant energy levels. The optical power distribution within the fiber is calculated by solving a set of partial differential equations using specially developed finite difference schemes that allow for a direct inclusion of the step discontinuities appearing at the fiber facets. The results obtained allow for a thorough analysis of luminescence from lanthanide ion doped chalcogenide fibers.

The 732 nm laser structure consists of a tensile strained GaAsP QW with AlGaAs confinement and cladding regions. The 975 nm structure comprises a strained InGaAs QW embedded in an Al-free optical cavity Both designs employ a large optical cavity to reduce the fast axis divergence and to decrease the tendency to filamentation, with similar values for the vertical confinement factor.

Supercontinuum is generated in concatenated ZBLAN and As2Se3 fibers. Initially, a 0.9-4.1mm supercontinuum is obtained by pumping the ZBLAN fiber with a Tm laser, which then continues to broaden to 0.9-9mm in As2Se3 fiber.

We present a data on the spectra and thresholds of two optically coupled microdisk lasers. The study is based on the reduction of the 3D lasing eigenvalue problem to a 2D one, through the effective index approximation. The latter problem is formulated in rigorous manner for Maxwell's equations with transmission boundary conditions at the disk boundaries and the radiation condition at infinity.

Mirror facets of broad area AlGaAs SQW 808 nm lasers with fast degradation of the output power have been investigated by photoluminescence microscopy (PLM), electroluminescence microscopy, and micro-photocurrent spectroscopy techniques. Over 2000 images of the photoluminescent light emitted from the facets of approximately 20 degraded laser bars have been made. Repeating patterns associated with the degradation have been noted and classified. Degraded lasers have dark lines on the mirror facet surface which are inclined from the epitaxial plane by 55°. Pairs of such lines often form V-shaped patterns. The orientation of the observed features suggest they are planar or line defects lying the the {111} crystallographic planes. The defects demonstrate a reduction in the lifetime of nonequilibrium electron–hole pairs and increased density of states in the forbidden gap of the active region of the laser structure, and are directly related to laser failure. Observations of the evolution in size and contrast of ...

The equivalence between the propagation of dispersive modal fields in two-dimensional waveguides, and plane waves in a one-dimensional plasma is presented. Exploitation of this equivalence allows a time domain variant of the effective index approach to be used to model dispersive waveguides problems very efficiently. A time domain integral equation is developed for this important practical case and the stability of a computer algorithm based upon it is improved by means of both a semi-implicit formulation and the use of a modified space–time mesh.

Summary from only given. For the design and optimisation of laser structures predictive models are needed. Previous models which have the potential to reproduce results have been obtained experimentally. However the accuracy and generality of these models are limited by the use of the paraxial approximation in the beam propagation algorithms and reliance on a phenomenological electronic model based on 1D lateral carrier diffusion in the active region. In the laser model presented in this paper, both limitations have been addressed. The simulation results are shown to agree well with experiment. The model solves consistently the optical, electrical and thermal equations for tapered lasers, taking into account the carrier and temperature induced refractive index changes.

Chalcogenide glass fibres have been demonstrated as a suitable medium for the realisation of spontaneous emission sources for mid-infrared photonics applications with a particular emphasis on sensor technology. Such sources give a viable alternative to other solutions due to their potentially low cost, high reliability and robustness when pumped using commercially available semiconductor lasers. We present a comprehensive analysis of the properties of selenide-chalcogenide glass fibres applied as spontaneous emission sources. We extract the modelling parameters from measurements using in house fabricated bulk glass and fibre samples. We apply the well-established rate equations approach to determine the level populations, the distribution of the photon intensity within the fibre and the output power levels. We compare the modelling results with experiment.

There are a number of reasons why a numerical value is a desirable outcome for the validation of numerical models: these include the desire to report objectively and succinctly on the comparison with a benchmark result, and the need to rank order implementations of a canonical problem. The key challenge is to develop techniques which provide a numerical output that do not challenge excessively the interpretations of experienced engineers and which presents both sufficient discrimination between comparisons and consistency across the various sub-disciplines of EMC. While this paper concentrates on the subject of numerical code generation, the rationale and associated concepts are just as relevant to other aspects of EMC such as quantifying experimental repeatability. The purpose of this paper is to present some of the work done to date on generating a numerical value representing the overall quality of comparison for two sets of data. This paper reviews and contrasts various techniques currently available to produce this numerical overview. The techniques include correlograms, feature selective validation (FSV), integrated error against log frequency (IELF) and reliability factors. The paper concludes that the most taxing aspect of the work required to develop such techniques is benchmarking against human interpretation, a rating scale is discussed which can assist in obtaining this information.

We demonstrate WG-modes degeneracy removal with simultaneous Q-factor enhancement in optimally-tuned symmetrical photonic molecules and directional emission from asymmetrical ones. Applications of such molecules to semiconductor, evanescent-wave-coupled-gain and random lasers, and biosensors are discussed.

Dielectric loaded cavities are used widely in such diverse applications as communications systems and microwave heating. Generally, they may have nontrivial geometries with multiple lossy dielectrics, feed points, etc., making detailed analytical study intractable. The paper presents a numerical modelling analysis, based on the transmission line modelling (TLM) method, of a realistically dimensioned generic resonator structure. The benefits to be gained in the understanding of the behaviour of the resonator structure from this type of approach are highlighted. Comparisons of experimental results with those obtained using the TLM show very good agreement for the location of the resonances, identification of mode interaction and the magnitude of the voltage standing wave ratio (VSWR) in the resonator feed point. This establishes TLM as a valuable diagnostic aid and preprototype design tool for dielectric loaded resonant cavities.

An advanced steady state semiconductor laser model is used to analyse the characteristics of high power laser diodes used for pumping erbium doped amplifiers. The laser model solves the bipolar current continuity equations in the bulk and quantum well regions, the thermal conduction equation and the optical wave equation in the travelling wave approximation using the 2D wide-angle beam propagation method. In this paper, we demonstrate that a small beam spoiler offset or mirror tilt results in a significant asymmetry of the near field patterns.

It is shown that ray theory can be used in designing a microwave horn with a hyperbolic secant refractive-index profile. The horn is short in length, has constant phase across the plane aperture and tapered illumination in the E-plane, resulting in a radiation pattern with low sidelobes. Experimental verification has been made on a model operating around a frequency of 10 GHz.

A new design based on ray theory is presented for a phase corrected horn antenna which is shorter than one with a hyperbolic secant refractive index profile. A dielectric load is essential for realistic implementation. With load permittivity decreasing linearly towards the aperture, a smooth flared profile can be obtained. The antenna's compactness makes it useful for marine applications.