The Experts below are selected from a list of 26571 Experts worldwide ranked by ideXlab platform
Yusuf Ziya Umul - One of the best experts on this subject based on the ideXlab platform.
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wave diffraction by a soft hard strip modified theory of physical optics solution
Optik, 2018Co-Authors: Yusuf Ziya UmulAbstract:Abstract The scattering problem of waves by a strip, the faces of which are composed of soft and hard surfaces, is investigated by the method of modified theory of physical optics. The scattering integral is divided into two parts according to the single effects of the faces. The boundary conditions are integrated into the integrals and the Resultant Field expressions are obtained by the asymptotic evaluation methods. The scattered waves are examined numerically.
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Wave diffraction by a soft/hard strip: Modified theory of physical optics solution
Optik, 2018Co-Authors: Yusuf Ziya UmulAbstract:Abstract The scattering problem of waves by a strip, the faces of which are composed of soft and hard surfaces, is investigated by the method of modified theory of physical optics. The scattering integral is divided into two parts according to the single effects of the faces. The boundary conditions are integrated into the integrals and the Resultant Field expressions are obtained by the asymptotic evaluation methods. The scattered waves are examined numerically.
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Wave diffraction by a right-angled interface between resistive half and whole planes
AEU - International Journal of Electronics and Communications, 2018Co-Authors: Yusuf Ziya UmulAbstract:Abstract The interaction phenomenon of electromagnetic plane waves by a right angled interface between whole and half screens with different resistivities is studied. The construction, under examination, is considered in order to model various corner discontinuities between transmissive surfaces for indoor wireless communications. First of all, the initial waves, which occur in the absence of the diffracting edge, are determined. Then the scattered geometrical optics Fields are obtained by subtracting the initial waves from the total geometrical optics Fields. The diffracted Field is constructed directly from the scattered geometrical optics wave by a new method. The Resultant Field expressions are examined numerically.
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A uniform function for the diffraction of spherical waves
Optik, 2017Co-Authors: Yusuf Ziya UmulAbstract:Abstract A function which occurs in the scattering problem of the spherical waves by a perfectly conducting half-plane is introduced for constructing the transition functions of the uniform theory of diffraction and uniform asymptotic theory of diffraction. The important properties of the function, related with the geometrical optics and diffracted Field components, are derived mathematically. A uniform asymptotic theory of wedge diffraction is introduced based on the new function. The Resultant Field expressions are investigated numerically.
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Wave diffraction by material half-planes
Optik, 2017Co-Authors: Yusuf Ziya UmulAbstract:Abstract The diffraction of E -polarized electromagnetic waves by resistive and conductive half-planes is studied. The solution of Maliuzhinets for the scattering problem of plane waves from an impedance half-screen is taken into account. The diffracted Fields from the resistive and conductive half-planes are obtained by using a relation between the scattered waves from material surfaces. The integrals of scattering are also constructed in the complex plane. The Resultant Field expressions are compared with the literature numerically.
Tomohiro Shirai - One of the best experts on this subject based on the ideXlab platform.
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Some consequences of the van Cittert-Zernike theorem for partially polarized stochastic electromagnetic Fields.
Optics Letters, 2009Co-Authors: Tomohiro ShiraiAbstract:Coherence and polarization properties of the Field generated by a partially polarized incoherent source are examined in terms of the 2×2 cross-spectral density matrix, with a view to deriving an electromagnetic counterpart of the van Cittert-Zernike theorem. Emphasis is placed on the polarization properties of the Field. As some consequences of the extended theorem, we found that the spectral degree of polarization of the Resultant Field is generally different from that of the source and that both are the same in a special case. A different somewhat unconventional view of the extended theorem is also discussed in brief.
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Modification of Spatial Coherence by Means of Low-Order Zernike-Mode Adaptive Optics
Optical Review, 2004Co-Authors: Tomohiro ShiraiAbstract:Spatial coherence of the Field modified by low-order adaptive optics is analyzed to establish a theoretical basis for the recent idea of using adaptive optics as a spatial coherence modifier. In this context low-order adaptive optics has the ability to correct some of the low-order aberrations specified by Zernike polynomials. The initial Field to be modified is assumed to be a spatially partially coherent one resulting from phase disturbance. It is demonstrated, as in the previous study, that low-order adaptive optics serves to enhance the spatial coherence of the Resultant Field and that the effect of the enhancement becomes stronger as the spatial coherence of the initially partially coherent Field increases. Potential applications of low-order adaptive optics as a spatial coherence modifier are briefly discussed.
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Adaptive Optics as a Spatial Coherence Modifier
Optical Review, 2004Co-Authors: Tomohiro Shirai, Christopher DaintyAbstract:The possibility of adaptive optics as a spatial coherence modifier is discussed. The initial Field to be corrected is produced in such a way that a quasi-monochromatic plane wave of light is incident on a moving diffuser plate, so that it is spatially partially coherent. It is shown that adaptive optics serves to enhance the spatial coherence of the Resultant Field and that the magnitude of the enhancement depends on the spatial coherence of the initial Field to be corrected. The results are illustrated by numerical examples based on an idealized low-order adaptive optics system.
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Spectral Changes of Light Produced by Multiple Scattering from Space-Time Fluctuating Random Media under the Born Approximation
Optical Review, 1996Co-Authors: Tomohiro Shirai, Toshimitsu AsakuraAbstract:Changes in the spectrum of light scattered by space-time fluctuating random media are investigated theoretically within the accuracy of the second-order Born approximation, as a continuation of the previous paper [Opt. Commun. 123 (1996) 234]. Effects of multiple scattering on the Resultant Field are manifested by a number of illustrative examples. It is shown, in particular, that the spectrum of the scattered light to be observed under practical circumstances is distorted by the process of multiple scattering. Comparison between spectra of both single and multiple scattering lights is also presented in the framework of the dynamic scattering.
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Multiple light scattering from spatially random media under the second-order Born approximation
Optics Communications, 1996Co-Authors: Tomohiro Shirai, Toshimitsu AsakuraAbstract:An expression is derived for the statistically-averaged spectral density of light produced by scattering from spatially random media within the accuracy of the second-order Born approximation. On the basis of the expression derived, effects of multiple scattering on the Resultant Field are investigated by some numerical examples. In particular, spectral changes of the scattered Field are examined with reference to the correlation-induced spectral changes of the Wolf effect. Numerical examples to be illustrated clearly demonstrate that the feature of the Resultant Field varies, depending strongly on the process of multiple scattering.
K.e.k. El-damanawi - One of the best experts on this subject based on the ideXlab platform.
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The Uniformly Moving Edge Dislocation
ZAMM, 2001Co-Authors: M. A. Jaswon, K.e.k. El-damanawiAbstract:The classical elastostatic displacement Field has a biharmonic character conveniently expressed by the Papkovich-Neuber formula. This can be readily transformed into the superposition of two distinctive biharmonic components. These can be exhibited as the limits of uniformly moving wave Fields, which are then coupled together to provide an acceptable Resultant Field. Our approach has been successfully applied to recover Easons', solution for a uniformly moving point force, and it is here applied to recover Eshelby's solution for a uniformly moving edge dislocation.
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Uniformly Moving Elastic Singularities In TheClassical Theory Of Elasticity
1998Co-Authors: M. A. Jaswon, K.e.k. El-damanawiAbstract:The classical elastostatic displacement Field has a biharmonic character, conveniently expressed by the Papkovich-Neuber formula. This can be quickly transformed into a Stokes-Helmoltz representation involving the superposition of two distinctive biharmonic vectors. These can be exhibited as the limits of uniformly moving Fields, which are then coupled together to provide an acceptable Resultant Field i.e. it satisfies the Navier-Cauchy equations; it reduces to the static limit for a vanishing velocity; and it can be rearranged into Lame's representation involving the superposition of two distinctive wave vectors. Some well well known results of Eshelby,and of Eason et al, obtained by Fourier transform methods, have been recovered by this approach and some further results achieved.
W Steenaa - One of the best experts on this subject based on the ideXlab platform.
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analysis of n n passive optical star coupler based on the normal modes of n input waveguides
Journal of Lightwave Technology, 1992Co-Authors: K K H Lee, W SteenaaAbstract:An integrated passive N*N optical star coupler on silicon wafer is described. Antiresonant reflecting optical waveguides (ARROWs) are analyzed and utilized as the input and output waveguides of the N*N coupler. Combining the exact solutions of the slab ARROW waveguide with the effective index method, a 5*5 coupler is analyzed. In the slab waveguide analysis, the input waveguides are coupled to their neighbors. The interaction of the waveguides is described in terms of the normal modes of propagation. The Resultant Field distribution is then diffracted into the free space region which separates the input and output sections. The radiation illuminates the receiving aperture from which the receiving N waveguides branch out, each output element obtaining equal power levels. Different types of loss such as spillover loss and mismatch loss were analyzed and estimated for N=5. A 5*5 star coupler with a transmission efficiency of 56% at a wavelength of 1.3 mu m is achievable. >
Jianjun Jia - One of the best experts on this subject based on the ideXlab platform.
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Extension of the van Cittert–Zernike theorem for completely polarized incoherent electromagnetic beam propagating through non-Kolmogorov turbulence
Optik, 2011Co-Authors: Yuanguang Wang, Yixin Zhang, Jianyu Wang, Jianjun JiaAbstract:Abstract Based on the 2 × 2 cross-spectral density matrix, the van Cittert–Zernike extended theorem is developed for the completely polarized incoherent beams propagation through the paraxial non-Kolmogorov turbulence. On the consequence of the extended theorem and the definition of general spectral degree of cross-polarization of a beam, we found that the spectral degree of cross-polarization of the Resultant Field is independent of the refractive index structure constant of atmospheric turbulence. We investigated the influences of the propagation distance and the distance of two detection points on the degree of coherence and the spectral degree of cross-polarization.
