Browsing by Author "Umul, Yusuf Z."

Now showing 1 - 20 of 47

Citation - WoS: 22
Citation - Scopus: 23
Alternative Interpretation of the Edge-Diffraction Phenomenon
(Optical Soc Amer, 2008) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
An alternative interpretation of the phenomenon of edge diffraction is proposed according to a new separation of the Fresnel function. The subfields are investigated in the problem of diffraction of a plane wave by a perfectly conducting half-plane, and the results are compared numerically with other interpretations. (c) 2008 Optical Society of America.
Citation - WoS: 7
Citation - Scopus: 8
Apertured Paraxial Bessel Beams
(Optical Soc Amer, 2010) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The paraxial Bessel beam is obtained by applying an approximation in the wavenumbers. The scattering of the beams by a circular aperture in an absorbing screen is investigated. The scattered fields are expressed in terms of the Fresnel integrals by evaluating the Kirchhoff diffraction integral in the paraxial approximation. The results are examined numerically. (C) 2010 Optical Society of America
Citation - WoS: 4
Citation - Scopus: 5
Application of the Complex Point Source Method To the Schrodinger Equation
(Elsevier Sci Ltd, 2010) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The paraxial wave equation is a reduced form of the Helmholtz equation. Its solutions can be directly obtained from the solutions of the Helmholtz equation by using the method of complex point source. We applied the same logic to quantum mechanics, because the Schrodinger equation is parabolic in nature as the paraxial wave equation. We defined a differential equation, which is analogous to the Helmholtz equation for quantum mechanics and derived the solutions of the Schrodinger equation by taking into account the solutions of this equation with the method of complex point source. The method is applied to the problem of diffraction of matter waves by a shutter. (C) 2010 Elsevier Ltd. All rights reserved.
Citation - WoS: 14
Citation - Scopus: 15
Closed Form Series Solution of the Diffraction Problem of Plane Waves by an Impedance Half-Plane
(Iop Publishing Ltd, 2009) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The scattering problem of plane waves by an impedance half-plane is solved by using the method of separation of variables, and a closed form series expression, which separately reduces to the cases of soft and hard half-planes, is obtained. The results are investigated numerically and compared with the solutions in the literature.
Comment on "a Survey of the New Proposal About the Photon Momentum" (Vol 148, Pg 342, 2017)
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Citation - WoS: 5
Citation - Scopus: 5
Comments on "on the Modified Theory of Physical Optics
(Ieee-inst Electrical Electronics Engineers inc, 2014) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Comparison of Diffraction Methods for Lunar Occultations
(Elsevier Gmbh, 2020) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The only analytical method, which is used for the mathematical analysis of lunar occultations, is the Fresnel diffraction. The Fresnel integral is derived from the diffraction integral of Kirchhoff under some approximations. This paper aims to compare this method with the exact solution of Sommerfeld, which is obtained for a perfect electric conductor half-plane. The geometrical optics and diffracted fields are expressed separately. Numerical simulations are given for the comparison of two different total and diffracted waves.
Diffraction in Time of Matter Waves Located in a Confined Region
(Springer Heidelberg, 2022) Umul, Yusuf Z.; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The process of diffraction in time of a standing matter wave is studied. This case occurs generally when a quantum particle is confined in a trap or infinite potential well. First of all, the wave-function of a classical time diffracted matter wave is studied by considering a separation of the Fresnel function in terms of geometrical optics and diffracted waves. The behavior of the matter wave which is the counterpart of a geometrical optics field is investigated. Then a confined particle in a one-dimensional infinite potential well is taken into account. One of the walls of the trap is remained at an initial time and the process of diffraction in time is formulated by using the information, obtained from the geometrical optics fields. Some numerical results are given. This paper proposes two original approaches. The first one is the application of the optical diffraction theory to quantum physics. This is the separation of the scattered field into geometric optics and diffracted wave components. The second novelty is the addition of the effects of both of the traveling waves, which compose the standing wave, to the scattering integral.
Citation - WoS: 2
Citation - Scopus: 2
Diffraction of Electromagnetic Waves by an Anomalously Transmitting Metasurface Half-Plane in Anisotropic Plasma
(Elsevier Gmbh, 2020) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The paper deals with the scattering of magnetic polarized electromagnetic plane waves by a anomalously transmitting metasurface half-plane, located in anisotropic plasma. Such a medium occurs for cold magnetized plasma, in which a static magnetic field exists. In this case the permittivity of the medium is expressed as a tensor, the elements of which are functions of the magnetostatic field, electron's mass and charge and angular frequency of the plasma. The metasurface half-plane transmits part of the incoming electromagnetic wave with a different angle from the angle of incidence, absorbing the remaining part. First of all, we will obtain the scattered geometric optics wave by subtracting the incident field from the total geometric optics wave. Then the kernel of a physical optics type scattering integral will be constructed with the aid of the integral theory of diffraction. The uniform diffracted magnetic field will be obtained from the physical optics integral. The total magnetic field will be evaluated as a sum of the total geometric optics and diffracted waves. The behaviours of the derived fields will be analyzed numerically.
Citation - WoS: 34
Citation - Scopus: 37
Diffraction of Evanescent Plane Waves by a Resistive Half-Plane
(Optical Soc Amer, 2007) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Diffraction of evanescent plane waves by a resistive half-plane is examined. The scattering integrals are constructed with the modified theory of physical optics. These integrals are evaluated uniformly by using an unusual method. The scattered fields of evanescent waves are obtained by giving the angle of incidence a complex value. The diffracted waves are plotted numerically for different parameters of the incident field. (c) 2007 Optical Society of America.
Citation - WoS: 8
Citation - Scopus: 8
Diffraction of Homogeneous and Inhomogeneous Plane Waves by a Planar Junction Between Perfectly Conducting and Impedance Half-Planes
(Optical Soc Amer, 2007) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The problem of diffraction of homogeneous and inhomogeneous plane waves at the discontinuity formed by perfectly conducting and impedance half-planes is examined by the method of modified theory of physical optics (MTPO). The MTPO integral of the reflected scattered waves by the perfectly conducting half-plane is reconstructed in order to include the effect of the diffracted wave coming from the edge of the impedance halfplane. The integrals are evaluated by a uniform asymptotic method. The results are plotted numerically and compared with the literature. (C) 2007 Optical Society of America
Citation - WoS: 3
Citation - Scopus: 4
Diffraction of Plane Waves by a Black Wedge
(Elsevier Sci Ltd, 2010) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The scattering of plane waves by a black wedge is examined. Two methods are considered for the solution of the problem. A closed-form series solution is derived by performing the technique of the separation of variables using boundary conditions of Macdonald. The second approach is the method of the modified theory of physical optics. The results are compared numerically. (C) 2009 Elsevier Ltd. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 2
Diffraction of Plane Waves by the Interface Between Black and Soft/Hard Semi-Planes
(Elsevier Gmbh, 2012) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A theory of scattering, based on the non-perturbation of the incident field, is developed for the black bodies. The method is applied to the diffraction problem of plane waves by an interface between the black and soft/hard half-planes. The solutions are obtained in terms of infinite series and then transformed into Fresnel integrals. The scattered fields are investigated numerically. (C) 2011 Elsevier GmbH. All rights reserved.
Citation - WoS: 15
Citation - Scopus: 15
Diffraction of Waves by a Resistive Half-Plane
(Elsevier Science Bv, 2014) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The scattered waves by a resistive half-plane are investigated with defining reflection and transmission coefficients for the diffracted waves. The coefficients are determined according to suitable conditions that are derived from the boundary conditions and the limiting cases of the reflection and transmission coefficients of the geometrical optics fields. The resultant field expressions are examined and compared with the literature numerically. (C) 2014 Elsevier By All rights reserved.
Citation - WoS: 23
Citation - Scopus: 24
Edge-Dislocation Waves in the Diffraction Process by an Impedance Half-Plane
(Optical Soc Amer, 2007) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Edge-dislocation waves, created in the diffraction of plane waves by an impedance half-plane, are examined by the method of modified theory of physical optics. The integrals, obtained by a related technique, are decomposed according to their boundaries and evaluated by using uniform asymptotic methods. The results are plotted and are investigated numerically. (c) 2007 Optical Society of America
Citation - WoS: 11
Citation - Scopus: 11
Effect of the Shadow Geometry in Wedge Diffraction
(Optica Publishing Group, 2009) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The surface integrals of the modified theory of physical optics are divided into two parts for diffraction by a wedge. Each integral represents the incident or reflected field scattered by one of the faces of the wedge. The results are investigated numerically and compared with the uniform theory of diffraction. (C) 2009 Optical Society of America
Citation - WoS: 15
Citation - Scopus: 15
Effect of the Shadow Geometry on Diffraction
(Optical Soc Amer, 2008) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The effect of the scatterer surface on the shadow region is examined by using the surface integrals of the modified theory of physical optics. It is shown that the shadow geometry has a considerable effect on the structure of the edge diffracted waves. The diffracted fields for the illuminated and shadowed surface of a half-plane are evaluated in terms of Fresnel integrals and plotted numerically. (C) 2008 Optical Society of America
Citation - WoS: 4
Citation - Scopus: 4
Fictitious Diffracted Waves in the Diffraction Theory of Kirchhoff
(Optical Soc Amer, 2010) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The diffraction theory of Kirchhoff is applied to the semi-infinite aperture of a black half-screen. The derivative of the spherical Green's function is taken into account without any approximation. The uniformly evaluated scattering integral is compared with the physical optics solution. It is shown that the non-omitted term causes the existence of fictitious diffracted waves. (C) 2009 Optical Society of America
Citation - WoS: 5
Citation - Scopus: 5
Fringe Waves in Wedge Diffraction
(Elsevier Gmbh, Urban & Fischer verlag, 2012) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Explicit expressions for the non-uniform currents of the physical theory of diffraction are derived in terms of Fresnel functions for wedge diffraction by taking into account the surface integrals of the modified theory of physical optics. The obtained fringe waves are compared numerically by the asymptotic representations, found in the literature. (C) 2011 Elsevier GmbH. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 4
General Formulation of the Edge-Diffracted Paraxial Waves
(Elsevier Sci Ltd, 2009) Umul, Yusuf Z.; 42699; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A general formula for edge-diffracted paraxial waves is derived in terms of the Fourier integral transform. It is observed that the scattered paraxial wave can be divided into components of the geometrical optics and diffracted fields in the spectral domain. An edge-diffracted Gaussian beam is examined numerically as an application of the formula. (C) 2008 Elsevier Ltd. All rights reserved.