A.J. Giarola

University of Campinas, Conceição de Campinas, São Paulo, Brazil

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Publications (83)54.28 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The main objective of this paper is to show that, with the use of a one-dimensional grating, having uniaxial dielectric anisotropy, it is possible to change the frequency of the maximum reflection transmission peak of an incident wave with a TM polarization, while maintaining the corresponding frequency of an incident TE wave fixed, without the need to change the grating geometry. This will allow the design of optical filters that are independent of the incident light polarization. A rigorous modal theory is used, such that the fields propagating in the various regions of the structure are represented as a summation of infinite models. It is shown that polarization independence is achieved by conveniently choosing the value of the grating dielectric ratio anisotropy ratio εxx/εzz. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 86–89, 2001.
    Microwave and Optical Technology Letters 02/2001; 29(2):86 - 89. · 0.59 Impact Factor
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    ABSTRACT: A notebook in the software Mathematica is developed here for the analysis of planar multilayer dielectric waveguides with the objective of using it as a didactic computational tool, with a possible inclusion in the electrical engineering package library of this same software. The scattering and guiding phenomena in a given structure are analyzed in the notebook, through the use of the programming facilities of the Mathematica software. The user may thus specify the physical and geometrical parameters to be analyzed or make a choice from a model's library that includes periodic structures such as Bragg reflectors and multiple quantum well (MQW) structures
    IEEE Transactions on Education 12/1999; · 0.95 Impact Factor
  • R.G. Farias, A.J. Giarola
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    ABSTRACT: The finite-difference time-domain (FDTD) technique is applied to the analysis of planar dielectric waveguides controlled by means of an optical beam. This beam, with an appropriate energy, induces a nonuniform plasma in a semiconductor layer deposited on the waveguide core. The resulting effects are analyzed through the phase dispersion characteristics. Due to the complexity of the problem, the FDTD formulation does not allow the calculation of the attenuation characteristic, particularly when the plasma presents an intermediate density, which causes a strong interaction with the guided mode. The simulations shown here suggest that the light beam may have an effective control of the phase response of a single waveguide and of the coupling between two parallel coupled waveguides
    IEEE Transactions on Microwave Theory and Techniques 06/1999; · 2.23 Impact Factor
  • Ivan Torres Lima, Attílio José Giarola
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    ABSTRACT: Electromagnetic wave propagation in two-dimensional dielectric gratings, consisting of a periodic array of rectangular anisotropic dielectric waveguides, is examined here using an integral equation including the application of the moment method, the volume equivalence theorem, and an adequate electric field expansion inside each rectangular dielectric waveguide. Curves of normalized phase constant as functions of the normalized Floquet's wavenumber are obtained for various waveguide dimensions. Agreement is observed with existing results in the limit of the one-dimensional dielectric grating. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 329–333, 1999.
    Microwave and Optical Technology Letters 02/1999; 20(5):329 - 333. · 0.59 Impact Factor
  • Carlo Leônidas Da Silva Souza Sobrinho, Attílio José Giarola
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    ABSTRACT: The finite-difference in the frequency-domain (FD–FD) method is used here to study the propagation characteristics of an integrated channel waveguide, consisting of a plasma controlled by a magnetostatic field (magnetoplasma). The dependence relation between resonance and cyclotron frequency, collision frequency, channel dimensions, and plasma frequency is shown. The formulation is developed in terms of the transverse magnetic field components such that the problem is transformed into a conventional eigenvalue problem. The elimination of the spurious modes is obtained with the implicit inclusion of ∇⋅B=0. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 38–42, 1998.
    Microwave and Optical Technology Letters 12/1998; 19(1):38 - 42. · 0.59 Impact Factor
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    ABSTRACT: The finite-difference in the frequency-domain (FD-FD) method is used in the analysis of the dispersion characteristics of guided waves in periodic structures such as: photonic crystals and dielectric gratings. The propagation is considered along an arbitrary direction and the analysis of the propagating modes is divided into two cases: (1) longitudinal propagation, where the guided waves are hybrid modes; and (2) transverse propagation, where the guided waves are TE or TM modes. The structure consists of a lossless biaxial anisotropic dielectric and the refraction index profile may vary continuously. The formulation is developed in such a way as to transform the problem into a conventional eigenvalue problem. The formulation is then applied to various cases where the active mode coupling and forbidden propagating bands are identified.
    Antennas and Propagation Society International Symposium, 1998. IEEE; 07/1998
  • R.G. Farias, A.J. Giarola
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    ABSTRACT: The finite-difference time-domain (FDTD) method is used for the analysis of magnetoplasma rectangular channel waveguides. Single and parallel-coupled waveguides are considered. The effect of varying the amplitude and the orientation of the bias magnetic field B<sub>0</sub> on the dispersion characteristics of the first modes is examined. However, the FDTD formulation, does not excite evanescent modes for a sufficiently long time interval, particularly when in the presence of the propagating or dynamic modes. As a result, the nonreciprocal properties of these structures, primarily associated with the evanescent modes, could not be investigated
    IEEE Transactions on Microwave Theory and Techniques 05/1998; · 2.23 Impact Factor
  • C.L. da S.S. Sobrinho, A.J. Giarola
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    ABSTRACT: A finite-difference frequency-domain (FD-FD) formulation is developed to study the dispersion characteristics of anisotropic dielectric waveguides with their optical axes not aligned with the coordinate-system axes. In this analysis, the optical axes are initially assumed to be aligned with the coordinate-system axes such that the electric-permittivity and magnetic-permeability tensors are diagonal. The optical axes of the anisotropic dielectric are then rotated an angle θ (or φ) with respect to the coordinate-system axes. While the FD-FD formulation developed is general, it is applied here only to waveguides containing uniaxial anisotropic dielectrics. The results show that accurate optical-axis orientation is important in the design of dielectric waveguides
    IEEE Transactions on Microwave Theory and Techniques 11/1997; · 2.23 Impact Factor
  • I.T.L. Junior, A.J. Giarola
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    ABSTRACT: The electromagnetic wave propagation in a two dimensional dielectric grating, consisting of a periodic array of rectangular dielectric waveguides, is examined here using the moment method with an adequate electric field expansion inside each rectangular dielectric waveguide. The free space Green's function is obtained by using the volume equivalence theorem. It includes the waveguide coupling through the use of the Floquet's theorem. Curves of normalized phase constant as functions of Floquet's wavenumber are obtained for various waveguide dimensions. Agreement is observed with existing results in the limit of the one dimensional dielectric grating
    Microwave and Optoelectronics Conference, 1997. 'Linking to the Next Century'. Proceedings., 1997 SBMO/IEEE MTT-S International; 09/1997
  • M.E.V. Segatto, R.G. Farias, A.J. Giarola
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    ABSTRACT: The formulation of the finite difference time domain method (FDTD) for the analysis of propagation characteristic of rectangular waveguides filled with magnetized plasma is presented here. In this formulation the FDTD method is used for the numerical solution of Maxwell's equations in the time domain. As a result, the system of partial differential equations formed by the electric and magnetic field components is replaced by a system of finite difference equations that are solved iteratively. The results presented show a variation of the dispersion characteristics of the structures examined as functions of the plasma parameters
    Microwave and Optoelectronics Conference, 1997. 'Linking to the Next Century'. Proceedings., 1997 SBMO/IEEE MTT-S International; 09/1997
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    ABSTRACT: A Notebook developed in the Mathematica software using a rigorous formulation to analyze planar optical waveguides operating in the TE or TM mode is presented. By using the Mathematica facilities, it is possible to simplify the development for the calculation and visualization of the propagation constants and the field distribution. The user can specify the physical and geometrical waveguides parameters or use a set from a practical model library, including MQW waveguides. In this case, the results can be obtained from rigorous analysis or from approximations that reduce the MQW waveguide to an equivalent three-layer slab waveguide
    Microwave and Optoelectronics Conference, 1997. Linking to the Next Century. Proceedings., 1997 SBMO/IEEE MTT-S International; 09/1997
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    ABSTRACT: Frequency selective characteristics of multilayer anisotropic dielectric grating waveguides are analyzed here, having in mind their use as dichroic surfaces in the millimeter waveband. The rigorous formulation described by Costa and Giarola [1993-96] is extended to include biaxial anisotropic dielectrics with their optical axes aligned with the coordinate axes. Numerical results are shown for a sinusoidally varying dielectric constant in the grating. The effect of the dielectric anisotropy square ratio on the resonance anomalies of the diffraction curves is carefully investigated
    Microwave and Optoelectronics Conference, 1997. Linking to the Next Century. Proceedings., 1997 SBMO/IEEE MTT-S International; 09/1997
  • Torres Lima, A.J. Giarola
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    ABSTRACT: The electromagnetic wave propagation in dielectric gratings, consisting of a periodic array of rectangular anisotropic dielectric waveguides is examined. The free space Green's function is obtained using the equivalent volume current theorem and Floquet's theorem. An integral equation is obtained and solved using the moment method, with a proper choice of the basis functions for the field expansion inside the dielectric. The normalized phase constant is shown as a function of the normalized frequency for various geometrical parameters and dielectric anisotropy ratios. Comparison of some of these results with those existing for particular cases are also shown and a good agreement has always been observed
    Antennas and Propagation Society International Symposium, 1997. IEEE., 1997 Digest; 08/1997
  • J.C.W.A. Costa, A.J. Giarola
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    ABSTRACT: The scattered fields by multilayer dielectric grating waveguides show anomalies that causes total reflection within a small variation band of some given parameters, such as, frequency or incidence angle of the input signal. These anomalies are associated to a strong couple between any mode that could be excited in any waveguide layer and the incident wave. If the variation of the dielectric constant in the grating is small, the operating points, where there is occurrence of anomalies, may be estimated from the propagation characteristics of planar and uniform waveguides. Therefore is possible to project filters by adjusting the waveguides parameters for the occurrence of these anomalies by approximation
    Lasers and Electro-Optics Society Annual Meeting, 1997. LEOS '97 10th Annual Meeting. Conference Proceedings., IEEE; 01/1997
  • R.G. Farias, A.J. Giarola
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    ABSTRACT: A finite-difference time domain (FDTD) method is developed for the analysis of the electromagnetic wave propagation in semiconductor waveguides containing a magnetostatic-field controlled plasma. Dispersion characteristic curves are obtained for a variety of waveguides. However, since the FDTD formulation developed cannot excite evanescent modes for a sufficiently long time, only the dynamic or propagating modes are excited. As a result, the desired non-reciprocal effects, associated with these modes could not be examined
    Antennas and Propagation Society International Symposium, 1996. AP-S. Digest; 08/1996
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    ABSTRACT: The frequency selective characteristics of waveguides with a dielectric grating and operating with TM polarization are analyzed, having in mind their use as dichroic surfaces. The formulation is similar to that used to analyze waveguide structures operating with TE polarization. The results an valuable for the design of these structures
    01/1996;
  • Microwave and Optical Technology Letters - MICROWAVE OPT TECHNOL LETT. 01/1996; 12(6):350-353.
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    ABSTRACT: The aim of this work is to present a study of microstrip directional couplers on magnetized ferrites. The external dc magnetic field is assumed to be oriented in the y direction and its magnitude can be varied, allowing a magnetic control of the coupler properties. The Hertz vector potentials, oriented along the ferrite magnetization direction, are used to obtain the dyadic Green's function in an impedance matrix form. The numerical solution is based on Galerkin's method applied in the Fourier transform domain. Results are included as a function of structural parameters and of biasing magnetic field.
    Microwave Conference, 1995. 25th European; 10/1995
  • W.G. Barbosa, A.J. Giarola
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    ABSTRACT: A theoretical development is presented for the analysis of microstrip antennas on conical surfaces, operating in the TM<sub>10</sub> mode. The cavity model with magnetic side walls is used for the calculation of the resonant frequency and input impedance. The dyadic Green's function formulation is used to calculate the radiated fields and the radiation quality factor. Particular antennas me examined and numerical results for operation in the TM<sub>10</sub> mode are shown
    Microwave and Optoelectronics Conference, 1995. Proceedings., 1995 SBMO/IEEE MTT-S International; 08/1995
  • R.G. Farias, A.J. Giarola
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    ABSTRACT: The finite-difference time domain (FDTD) method for dispersive media is applied to the study of the electromagnetic wave propagation in optically-controlled coupled-dielectric-waveguides. The optical control is achieved by means of light incidence on semiconductor layers deposited onto the waveguides. The effects produced by the induced plasma in the semiconductor are analyzed through the dispersion characteristic of the waveguide structure
    Microwave and Optoelectronics Conference, 1995. Proceedings., 1995 SBMO/IEEE MTT-S International; 08/1995

Publication Stats

264 Citations
54.28 Total Impact Points

Institutions

  • 1983–2001
    • University of Campinas
      Conceição de Campinas, São Paulo, Brazil
  • 1988–1997
    • São Paulo State University
      • Departamento de Engenharia Elétrica (Bauru)
      Assis, Estado de Sao Paulo, Brazil
  • 1982–1996
    • Federal University of Pará
      • Program in Electrical Engineering
      Belém, Estado do Para, Brazil
  • 1981–1993
    • Universidade Federal do Rio Grande do Norte
      • • Department of Electrical Engineering
      • • Centro de Tecnologia
      Natal, Rio Grande do Norte, Brazil
  • 1982–1992
    • University of Brasília
      • Departamento de Engenharia Elétrica (ENE)
      Brasília, Distrito Federal, Brazil