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: 27Citation - Scopus: 28Field Correlations of Laser Arrays in Atmospheric Turbulence(Optical Soc Amer, 2014) Baykal, YahyaCorrelations of the fields at the receiver plane are evaluated after a symmetrical radial laser array beam incident field propagates in a turbulent atmosphere. The laser array configuration is composed of a number of the same size laser beamlets symmetrically located around a ring having a radius that determines the distance of the ring from the origin. The variations of the correlations of the received field originating from such laser array incidence versus the diagonal length starting from a receiver point are examined for various laser array parameters, turbulence parameters, and the locations of the reception points. Laser array parameters consist of the ring radius and the number and size of the beamlets. Structure constant, link length, and wavelength are the turbulence parameters whose effects on the field correlation of the laser arrays are also investigated. (C) 2014 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: 8Citation - Scopus: 9Cross Beam Scintillations in Non-Kolmogorov Medium(Optical Soc Amer, 2014) Baykal, YahyaFor the collimated and focused cross beams, the on-axis scintillation index is evaluated when these beams propagate in weak non-Kolmogorov turbulence. In the limiting cases, our solution correctly reduces to the known Gaussian beam scintillations in Kolmogorov turbulence. For both the collimated and the focused cross beams, large power law exponent of the non-Kolmogorov turbulence is found to result in larger scintillations. Evaluating at a fixed power law exponent, the scintillation index of the collimated (focused) cross beam is higher (lower) than the collimated (focused) Gaussian beam scintillation index. When the asymmetry of the collimated (focused) cross beam increases, the scintillations increase (decrease). At a given cross beam configuration, change in the turbulence parameters varies the scintillations in the same manner for all power law exponent values. (C) 2014 Optical Society of AmericaArticle Citation - WoS: 10Citation - Scopus: 9Structure Functions in Turbulence for Incidence With Arbitrary-Field Distribution(Optical Soc Amer, 2007) Baykal, YahyaIn a turbulent atmosphere, the log-amplitude, phase-correlation, and structure functions are formulated for light sources exhibiting arbitrary-field distribution. This is done by extending the formulations of the correlation and structure functions for the known general-type beam sources to cover any type of source having arbitrary-field distribution. To introduce the arbitrary field, the source is presented by an incidence that is a function of transverse source coordinates. The received field in the random medium is found by employing the Rytov method, which is a single-scattering solution obtained by the first-order approximation; thus our results are valid in weak turbulence. All the existing results can be correctly reproduced from our formulations when the corresponding source-field distributions are inserted into our presented correlation and structure-function expressions. Our results for the arbitrary-source field profiles can be utilized in finding the scintillation index and the angle-of-arrival fluctuations of any type of incidence in optical atmospheric links. Additionally, our formulations can find applications in reflection from rough surfaces and imaging in turbulence. (C) 2007 Optical Society of America