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The incorporation of material losses within an unstructured transmission line Modeling electromagnetic field solver is presented. A theoretical and numerical development is complemented by a number of quantified canonical examples. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2218–2222, 2015

Recently, particular attention has been given to metallic waveguides supporting surface plasmons as promising components for integrated optical devices. However, the use of conventional numerical optimization tools for their design is hindered by the intensive computational effort associated with meshing down to the resolution of the thin metallic layer. In this study, the previous three-point second order accurate finite-difference formula suitable for correctly placing thin dielectric layers within coarse grids is extended to fourth order accuracy by using the generalized Douglas scheme, including the case when thin metallic layers supporting surface plasmons lie wholly between sample points. The improved formulation, combined with an imaginary distance procedure, is used to analyze the eigenmodes of both 2D and 3D thin metal films located upon dielectric substrates. Accurate calculation with coarser meshes than those required by the other standard differencing schemes is demonstrated, thus providing both a significant saving in computational resource and an extra degree of freedom in meshing such structures.

A novel triangular TLM node containing a subcell sized wire of arbitrary radius is presented. The technique is based upon the mapping between the total field at the cell boundary and exact modal field expansions around the wire. The wire node is incorporated into an unstructured 2D TLM algorithm providing a flexible package for modeling fine-features in proximity to complex structures. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1753–1757, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23482

The behavior of a 2D model of an extended hemielliptic silicon lens of a size typical for THz applications is accurately studied for the case of a plane E-wave illumination. The full-wave analysis of the scattering problem is based on the Muller's boundary integral-equations (MBIE) that are uniquely solvable. A Galerkin discretization scheme with a trigonometric basis leads to a very efficient numerical algorithm. The numerical results related to the focusability of the lens versus its rear-side extension and the angle of the plane-wave incidence, as well as near-field profiles, demonstrate strong resonances. Such effects can change the principles of optimal design of lens-based receivers. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 515–518, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20520

An improved three-point finite-difference scheme is presented, which deals correctly with all terms up to 2nd order in the expansion of the derivative, regardless of the existence of multiple dielectric interfaces between sample points. The improved differencing scheme is implemented into a 1D slab-mode solver for validation of accuracy and a 2D mode solver. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 95–101, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20558

The ability to optimise the performance of today's opto-electronic circuits over a range of operational parameters and fabrication tolerances is foremost in the designer's mind. The ability to investigate the effects of tolerancing and integration upon device performance over a range of wavelengths is highly desirable for their successful exploitation. The spectral index (SI) method is a well-established method traditionally used for the analysis of the modal properties of semiconductor rib waveguides. In this paper the efficiency and accuracy of the SI method is exploited for the first time in a scattering-matrix approach to the analysis of complex integrated optical circuits. The SI approach yields highly accurate results with minimal computational effort. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 68–73, 2003

A wide-band finite-difference–time-domain beam propagation method (FD TD-BPM) based on Pade approximants is introduced to improve the bandwidth of the conventional TD-BPM. Numerical dispersion relations for the TD-BPM are derived to demonstrate the increase in bandwidth of the wide-band TD-BPM. The effects of the spatial and time step sizes on the numerical dispersion are also investigated. It is shown that the wide-band TD-BPM is less sensitive to the choice of spatial step size and allows a larger time step size to be used compared to the finite-difference time-domain (FD-TD) method. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 243–247, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10428

A novel finite-difference beam-propagation method (FD-BPM) algorithm for the analysis of photonics structures with sloped sides in the transverse plane is presented. By introducing nonorthogonal coordinate systems in the transverse plane, the staircasing effects inherent when one is modeling with a rectangular mesh are eliminated, and accuracy is substantially improved. The algorithm is tested in the analysis of sloped rib waveguides. The results obtained confirm the accuracy and high efficiency of the new algorithm. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 401–407, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10335

Both local SAR values for FDTD and RBFNN at 50 MHz and at 450 MHz are shown in Figures 4(a) and 4(b), respectively. These figures were drawn for the 300th cell that shows the center of x axis. Results obtained for these two methods are good in track. Based on this point, RBFNN model can provide automatic estimation of local SAR values in the working frequency values and requires coordinate location for each layer. This simulation was realized for three-layer cylindrical human model; however, this method can be easily used for different structures. Variation of maximum error levels which occur in the output of the network is shown in Figure 5. We have reached to these values by choosing maximum values between RBFNN results and FDTD results for each frequency in test step. Accuracy levels of the network changed with using different frequency values. In the designed model, the error level can be reduced by using an optimum sigma (width of the Gauss Kernel function) value. The variations are given in Figures 4 and 5 for 50. The test accuracy of RBFNN changes depending on the sigma parameter. The variation of maximum error values which is calculated for all frequency values in the test data with respect to sigma parameter is shown in Figure 6. The sigma is an effective parameter for the performance of network. The determination of optimum sigma values is important for the accuracy of the system. In this work, Gaussian Kernel width was determined experimentally for maximum performance. 5. CONCLUSION In this study, a new approach based on RBFNN was presented for the estimation of local SAR values for the three-layer cylindrical human model. The target data were determined with FDTD solution, which was used to determine the local SAR, when a plane wave hits the PML-surrounded three-layer cylinder. The results show that RBFNN is an effective model for this problem space, and RBFNN design solutions are well matched with the FDTD solution results. This method was proposed for the three-layer cylindrical human model; however, this topology can be applied for different structures. ACKNOWLEDGMENT

The free-space radiation mode method is extended to provide accurate semianalytical formulas for the reflectivity of a polarized optical waveguide mode incident on a coated laser facet at an arbitrary angle. Solutions may be obtained easily and with minimum computational effort. Results obtained are compared with those from a finite-difference-time-domain method. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 15: 12–16, 1997.

Numerical modeling has an important role to play in optical, microwave, and EMC design. An objective assessment of the accuracy of such numerical modeling tools using experimental data is often hampered by the general complexity of the data to be compared. It is therefore difficult to quantify the resulting comparisons. This communication suggests that three parameters derived from correlation functions can prove useful in assessing validation comparisons. © 1994 John Wiley & Sons, Inc.

A CAD package was developed that accepts a functional design specification for a multilayered optical slab waveguide and returns a physical description of a structure in a form immediately suitable for fabrication. It is shown that the definition of a figure of merit for the design requires that the importance of the design criteria be suitably weighted. The implications of the present work for the synthesis of more general optoelectronic components and circuits are discussed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 325–327, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10310

Curved optical waveguides are often fabricated or modeled as a succession of discrete linear segments connected at abrupt directional changes. A novel beam-propagation algorithm is presented that models the exact geometry of such a segmented curve. These results are compared with those from a continuous-curve algorithm and show the influence of the segmentation on curvature and transition losses. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 14, 202–204, 1997.

A nonorthogonal coordinate system that extends the present range of angled configurations for which the beam propagation method (BPM) is accurate is introduced. This offers an extra degree of freedom within configuration and method when the BPM is applied in the design of general photonic integrated circuits incorporating angled waveguide sections. © 1996 John Wiley & Sons, Inc.

A new simple method for the in situ measurement of the surface transfer impedance of coaxial cables is described. The method is based on injecting a disturbing current onto the outside of the test cable and measuring the corresponding voltage induced on the center conductor. It is shown to produce reliable results at frequencies up to 150 MHz with the use of a 1-m length of cable. ©1996 John Wiley & Sons, Inc.

A dielectric lens structure, the effective refractive index of which varies with its radius, is studied experimentally at millimeter-wave frequencies. The experimental results demonstrate that such a lens is suitable as a wideband compact power splitter for integrated optical circuits. © 1995 John Wiley & Sons, Inc.

A simple method for reducing the threshold current of vertical cavity surface-emitting lasers (VCSELs) is described. The approach modifies the top surface of the laser into a dome shape by chemical etching. This reduces the reflectance of the top mirror over an approximately annular region, thereby reducing the lasing area compared to the contact area in a controlled manner. A sevenfold reduction in threshold current over equivalent conventional VCSELs is demonstrated for a nonoptimized device that maintains a similar threshold current density. © 1995 John Wiley & Sons, Inc.