Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260
Browse
8 results
Search Results
Article Citation - WoS: 11Citation - Scopus: 10Modified Theory of the Physical-Optics Approach To the Impedance Wedge Problem(Optical Soc Amer, 2006) Umul, YZThe problem of a wedge with equal face impedances is examined with a modified theory of physical optics. The surface integral is constructed by use of the impedance boundary condition. The aperture equivalent current is estimated from the behavior of the reflected diffracted field. The integrals obtained are evaluated asymptotically and compared with the exact solution numerically. (c) 2006 Optical Society of America.Article Citation - WoS: 91Citation - Scopus: 96Scintillation Index of Elliptical Gaussian Beam in Turbulent Atmosphere(Optical Soc Amer, 2007) Cai, Yangjian; Chen, Yuntian; Eyyuboglu, Halil T.; Baykal, YahyaA tensor method is used to formulate the on-axis scintillation index for an elliptical Gaussian beam (EGB; astigmatic Gaussian beam) propagating in a weak turbulent atmosphere. Variations of the on-axis scintillation of an EGB are studied. It is interesting to find that the scintillation index of an EGB can be smaller than that of a circular Gaussian beam in a weakly turbulent atmosphere under certain conditions and is closely related to the ratio of the beam waist size along the long axis to that along the short axis of the EGB, the wavelength, and the structure constant of the turbulent atmosphere. (C) 2007 Optical Society of America.Article Citation - WoS: 2Citation - Scopus: 2Scattering of Inhomogeneous Plane Waves by a Resistive Half-Screen(Optical Soc Amer, 2013) Umul, Yusuf ZiyaThe scattering process of inhomogeneous plane waves by a resistive half-plane is investigated by using the exact diffracted field expressions. The uniform field representations are obtained with the aid of the uniform theory, put forward by Umul. The geometrical optics and diffracted and scattered fields are examined numerically. (C) 2013 Optical Society of AmericaArticle Citation - WoS: 25Citation - Scopus: 25Scintillations of Higher-Order Laser Beams in Non-Kolmogorov Medium(Optical Soc Amer, 2014) Baykal, YahyaIn an atmospheric medium that shows a non-Kolmogorov turbulence behavior, the variation of the on-axis scintillation index is evaluated when higher-order laser modes are used as the excitation. The Rytov method is employed together with the equivalent structure constant, which makes our results valid in weak turbulence. In the limiting case, our solution correctly reduces to the known scintillation index of the Gaussian beam in Kolmogorov turbulence. For all the higher-order even modes, increase in the power law exponent, a of the non-Kolmogorov spectrum is found to increase the scintillations. When the source size of the higher-order modes is large, higher-order even modes attain almost the same scintillation index values for all a. However, for small source sizes, being valid for any realization of the non-Kolmogorov spectrum, the scintillations decrease as the mode order becomes large. The changes in the propagation distance, structure constant, and the wavelength do not vary these trends. (C) 2014 Optical Society of AmericaArticle Citation - WoS: 13Citation - Scopus: 12Diffraction of Waves by a Boundary Between Two Half-Planes With Different Resistivities(Optical Soc Amer, 2015) Umul, Yusuf ZiyaThe solution of the diffraction problem of waves by a junction between two resistive half-screens is obtained by using the wedge diffraction field expression, introduced by Maliuzhinets [Ann. Phys. 461, 107 (1960)]. The two half-planes, located at the same coordinate plane, have different surface resistivities. The new field expression is compared with the solution of Senior ["Diffraction by a material junction,"http://deepblue.lib.umich.edu/handle/2027.42/21043] for the scattered waves. The important aspects of the approach are discussed in the light of the numerical results. (C) 2015 Optical Society of AmericaArticle Citation - WoS: 96Citation - Scopus: 101Twist Phase-Induced Reduction in Scintillation of a Partially Coherent Beam in Turbulent Atmosphere(Optical Soc Amer, 2012) Wang, Fei; Cai, Yangjian; Eyyuboglu, Halil T.; Baykal, YahyaThe scintillation index of a Gaussian Schell-model beam with twist phase (i.e., twisted GSM beam) in weak turbulent atmosphere is formulated with the help of a tensor method. Variations of the scintillation index of a twisted GSM beam on propagation in turbulent atmosphere are studied in detail. It is interesting to find that the scintillation index of a twisted GSM beam can be smaller than that without twist phase in weak turbulent atmosphere. Thus, modulation of the twist phase of a partially coherent beam provides a new way to reduce turbulence-induced scintillation. (C) 2012 Optical Society of AmericaArticle Citation - WoS: 69Citation - Scopus: 74Equivalence of Structure Constants in Non-Kolmogorov and Kolmogorov Spectra(Optical Soc Amer, 2011) Baykal, Yahya; Gercekcioglu, HamzaWe find the equivalence of the structure constants in non-Kolmogorov and Kolmogorov spectra in a turbulent atmosphere. As the reference point, the spherical wave scintillation index in a non-Kolmogorov medium is used. Relations of the structure constants are found to be functions of the power law of the turbulence spectrum and the Fresnel zone. It will be useful to employ the equivalence of the structure constants in making performance comparisons found with non-Kolmogorov and Kolmogorov spectra. (C) 2011 Optical Society of AmericaArticle Citation - WoS: 61Citation - Scopus: 66Evolution of the Degree of Polarization of an Electromagnetic Gaussian Schell-Model. Beam in a Gaussian Cavity(Optical Soc Amer, 2008) Yao, Min; Cai, Yangjian; Eyyuboglu, Halil T.; Baykal, Yahya; Korotkova, OlgaThe interaction of an electromagnetic Gaussian Schell-model (EGSM) beam with a Gaussian cavity is analyzed. In particular, the evolution of the degree of polarization of the EGSM beam is investigated. The results show that the behavior of the degree of polarization depends on both the statistical properties of the source that generates the EGSM beam and the parameter of the cavity. (C) 2008 Optical Society of America