Md. Ghulam Saber

Optimization of the optical properties of cuprous oxide and silicon-germanium alloy using the Lorentz and Debye models

The modeling parameters of cuprous oxide (Cu2O) and silicon-germanium (Si-Ge) alloy for the single-pole Lorentz model and the single-pole modified Debye model (MDM) are optimized and presented. A nonlinear optimization algorithm has been developed in order to optimize the parameters such that they are applicable to a wide frequency range. The obtained parameters have been used to determine the complex relative permittivity of the materials and compared with the experimental values. A very good agreement has been observed between the experimental values and the optimized parameters in the case of both the material models. The associated root mean square (RMS) deviations have been found to be as little as 0.15 and 0.08 for the Lorentz model and 0.1638 and 0.3710 for the modified Debye model respectively.

A Genetic Algorithm Based Approach for the Extraction of Optical Parameters

We present the Debye model parameters of four materials which are extensively used in the field of electronics and photonics. The parameters have been extracted using a Genetic Algorithm (GA) based technique. We have determined the complex relative permittivity using the extracted modeling parameters and compared with the experimentally obtained ones. A very good agreement has been found in each case which validates our extracted parameters. The associated root-mean-square (RMS) deviations have been found to be 0.3894, 0.026, 0.8163 and 0.4370 for graphene, graphene oxide, aluminum zinc oxide (AZO) and gallium zinc oxide (GZO) respectively.

Extraction of lorentz model parameters for dielectrics and their application in nanoplasmonics

The Lorentz model parameters for alumina, aluminum arsenide, zinc oxide, potassium bromide, graphene and gallium arsenide are optimized using a nonlinear optimization algorithm based on the Hooke and Jeeves method. The complex relative permittivity of each of the mentioned materials is calculated over a long wavelength range using the optimized parameters. The obtained permittivity curves exhibit very good match with those obtained from the experimental results. The symmetric SPP mode propagation through MDM waveguides containing alumina and aluminum arsenide as dielectric layers sandwiched between layers of silver has been investigated using their optimized modeling parameters.

Characteristics of Symmetric Surface Plasmon Polariton Mode in Glass–Metal–Glass Waveguide

The propagation characteristics of symmetric surface plasmon polariton mode in a glass–metal–glass waveguide are presented. Gallium lanthanum sulfide has been taken as the glass and silver (Ag) has been used as the metal. The analysis has been done both numerically and analytically. A two-dimensional finite-difference time-domain-based simulation model has been developed in order to analyze the propagation characteristics numerically. The obtained results using numerical and analytical methods have been compared and a very good agreement has been found.

Performance Analysis of a Differential Evolution Algorithm in Modeling Parameter Extraction of Optical Material

Determination of accurate modeling parameters of optical materials prior to defining the materials in the simulation model is fundamentally important to obtain simulation results close to the experimental ones. However, extracting modeling parameters of optical materials is inherently difficult because it involves fitting both real and imaginary parts of the relative permittivity using a single set of parameters. In this paper, an evolutionary algorithm called differential evolution (DE) has been utilized to extract the optical modeling parameters of graphene oxide. The performance of DE to find the optimal results has been analyzed by using different objective functions and boundary values. Two objective functions are used out of which one is proposed by us. Root-means-square (RMS) deviation, a measure of accuracy of the numerically obtained results has been determined for each case. From the obtained results it has been found that the DE algorithm extracted the optical modeling parameters successfully with very small RMS deviation for both real and imaginary parts of the complex relative permittivity.

A Comparative Study of Dispersion Characteristics Determination of a Trapezoidally Corrugated Slow Wave Structure Using Different Techniques

The linear dispersion relation of a trapezoidally corrugated slow wave structure (TCSWS) is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency range. The dispersion relation is solved by utilizing the Rayleigh–Fourier method by expressing the radial function in terms of the Fourier series. A highly accurate synthetic technique is also applied to determine the complete dispersion characteristics from experimentally measured resonances (cold test). Periodic structures resonate at specific frequencies when the terminals are shorted appropriately. The dispersion characteristics obtained from numerical calculation, synthetic technique and cold test are compared, and an excellent agreement is achieved.

Design of a Simple Integrated Coupler for SPP Excitation in a Dielectric Coated Ag Thin Film

A simple integrated coupler is proposed for the efficient excitation of surface plasmon polariton (SPP) mode in a thin metal film. The SPP mode is generated in a single Ag-dielectric interface by the incident field and coupled with an Ag thin film. The coupling efficiency at different wavelengths using two different dielectrics, gallium lanthanum sulfide (GLS) and aluminum gallium arsenide (AlGaAs) is calculated by analyzing the SPP propagation dynamics with the finite difference time domain method. A maximum coupling efficiency of 70% is obtained at a wavelength of 460 nm when GLS is used, whereas the corresponding value obtained for AlGaAs is 60% at 560 nm. The proposed structure can be used to excite SPPs in a nano-thin film from an external bulky source and is easier to fabricate since a single interface metal-dielectric configuration is used to excite the metal-thin film.

Numerical Investigation of SPP Propagation at the Nano-scale MDM Waveguides with a Combiner

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP

Modeling of Dispersive Materials Using Dispersion Models for FDTD Application

A nonlinear optimization algorithm based on the Nelder Mead method is used to characterize the frequency dependent permittivity of 15 materials based on Lorentz, modified Lorentz, Drude and Lorentz-Drude models. The optimized model parameters are used to calculate the complex relative permittivity of each material and compare it with experimental data. In each case, a very good match is found between the optimized and experimental data over a long wavelength range. Comparative study of the models used for each material is performed based on accuracy, wavelength range of applicability and computational efficiency. The parameters presented can be used for computer simulation of electromagnetic wave phenomena involving these materials.

Optimization of Lorentz model parameters for crystalline AS 2 S 3 , SiC and modified Lorentz model parameters for nanocrystalline SiO

We have presented the optimized Lorentz model parameters for crystalline arsenic sulfide (AS2S3), silicon carbide (SiC) and modified Lorentz model parameters for nanocrystalline silicon monoxide (SiO) obtained using a large scale non-linear algorithm. The complex relative permittivity calculated using the optimized parameters agree well with the experimental values over broad frequency bands. The associated RMS deviations are 0.254, 0.003, 0.010 and 0.009 respectively.