Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260
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Article Citation - WoS: 8Citation - Scopus: 8Radius of Curvature of Bessel and Modified Bessel Gaussian Beams(Elsevier Science Bv, 2013) Eyyuboglu, Halil Tanyer; Ji, XiaolingWe analyze the radius of curvature of Bessel Gaussian (BG) and modified Bessel Gaussian (mBG) beams. The study is based on the results of analytic derivation as well as those of the random phase screen approach. Our results are displayed in graphs as variations of radius of curvature against propagation distance at various settings of beam order, width parameter, source focal length, wavelength, refractive index structure constant. Our findings indicate that mBG beams, in general will have larger radius of curvature values than BG beams. It is further observed that increases in beam order will lead to greater radius of curvatures. Rises in the width parameter will reveal more the differentiations between BG and mBG beams. At small focal lengths, the difference between BG and mBG beams is hardly noticeable. Higher wavelengths will initially cause a reduction in the radius of curvature, but at longer propagation distances, the reverse will happen. Increases in the refractive index structure constant will lead to smaller radius of curvature values. A general agreement is found in comparing the analytic results of BG beams with those of phase screen approach. (C) 2013 Elsevier B.V. All rights reserved.Article Citation - WoS: 87Citation - Scopus: 94Scintillation Index of a Multi-Gaussian Schell-Model Beam in Turbulent Atmosphere(Elsevier, 2013) Yuan, Yangsheng; Liu, Xianlong; Wang, Fei; Chen, Yahong; Cai, Yangjian; Qu, Jun; Eyyuboglu, Halil T.Multi-Gaussian Schell-model (MGSM) beam was introduced recently [Sahin and Korotkova, Opt. Lett. 37 (2012) 2970; Korotkova et al., J. Opt. Soc. Am. A 29 (2012) 2159]. In this paper, an explicit expression for the scintillation index of a multi-Gaussian Schell-model (MGSM) beam in weakly or extremely strong turbulent atmosphere is derived with the help of a tensor method. Applying the derived formulae, the scintillation properties of a MGSM beam and a GSM beam in weakly or extremely strong turbulent atmosphere are studied numerically and comparatively. Our results show that a MGSM beam has advantage over a GSM beam for reducing turbulence-induced scintillation, which will be useful for long-distance free-space optical communications. (C) 2013 Elsevier B.V. All rights reserved.Article Citation - WoS: 16Citation - Scopus: 19Hypergeometric Gaussian Beam and Its Propagation in Turbulence(Elsevier Science Bv, 2012) Eyyuboglu, Halil Tanyer; Cai, YangjianWe study propagation characteristics of hypergeometric Gaussian beam in turbulence. In this context, we formulate the receiver plane intensity using extended Huygens-Fresnel integral. From the graphical results, it is seen that, after propagation, hypergeometric Gaussian will in general assume the shape of a dark hollow beam at topological charges other than zero. Increasing values of topological charge will make the beam broader with steeper walls. On the other hand, higher values of hollowness parameter will contract into a narrower shape. Raising the topological charge or the hollowness parameter individually will cause outer rings to appear. Both increased levels of turbulence and longer propagation distances will accelerate the beam evolution and help reach the final Gaussian shape sooner. At lower wavelengths, there will be less beam spreading. (C) 2012 Elsevier B.V. All rights reserved.