WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Article Comparison of the Unmodified Rytov Method and the Modified Rytov Method in Obtaining Scintillations in Various Strongly Turbulent Media(Optica Publishing Group (Formerly OSA), 2026) Baykal, Y.The scintillation index as evaluated by the unmodified (classical) Rytov method solution for weak turbulence and evaluated by the modified or the extended Rytov method solution for strong turbulence is compared in different turbulent media, such as non-Kolmogorov atmospheric, non-Kolmogorov jet engine exhaust, marine atmospheric, and oceanic turbulences. When the scintillations are evaluated against the turbulence strength for various non-Kolmogorov power law and source sizes, the distinction between the modified Rytov and the unmodified Rytov method solutions, as the strength of turbulence increases, is clearly observed in all the turbulent media. This distinction is emphasized when the comparison is made at larger power law and source sizes. The results in this paper will be helpful in optical wireless communication system performance evaluations. © 2025 Optica Publishing Group.Article Field Correlations of a Gaussian Vortex Laser Beam in Vertical Turbulent Oceanic Links(Optica Publishing Group (Formerly OSA), 2026) Gerçekcioǧlu, H.; Baykal, Y.Utilizing the extended Huygens–Fresnel principle, field correlations of a Gaussian vortex beam propagating in the vertical turbulent oceanic link are examined analytically and evaluated by simulation in the Atlantic Ocean at low- and mid-latitude and high-latitude summer. Our formulation is based on the coherence length of a spherical wave operating at the depth range between 3000 and 3500 m. Variations in the rate of dissipation of turbulent kinetic energy per unit mass of fluid ε, the rate of dissipation of the mean-squared temperature χT, and the ratio of temperature to salinity contributions to the refractive index spectrum ω are taken into account at these depths in the underwater turbulent medium. The field correlation obtained using the coherence length found with the help of the depth-dependent power spectrum is expressed in detail. When the topological charge is selected considering the source size and propagation distance, it is seen that the normalized field correlation of the Gaussian vortex beam gives better results as compared to Gaussian beams. © 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.Article Field Correlations in Jet Engine Exhaust Turbulence(Optica Publishing Group (Formerly OSA), 2026) Baykal, Y.Field correlations of collimated Gaussian beams are formulated and examined in jet engine exhaust turbulence. Variations of the field correlations are evaluated against the changes in the parameters of the wireless optical communication link and the jet engine exhaust turbulence. It is found that for all the link and turbulence parameters of interest, as the diagonal distance at the receiver plane increases, the field correlation decreases. Also, at the same diagonal distance from the receiver plane, field correlations tend to become smaller as the receiver points are at a larger distance from the receiver origin, at a smaller source size, wavelength, and inner scale values of jet engine exhaust turbulence. On the other hand, field correlations have a tendency to attain larger values at smaller link length, structure constant, amplitude coefficient for the additional high frequency spectrum area, outer scale of inhomogeneity, and the outer scale values of jet engine exhaust turbulence. © 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.Article Citation - WoS: 27Citation - Scopus: 28Beam Wander of J 0- and I 0-Bessel Gaussian Beams Propagating in Turbulent Atmosphere(Springer, 2010) Eyyuboglu, H. T.; Baykal, Y.; Korotkova, O.; Cai, Y.; Cil, C. Z.Root mean square (rms) beam wander of J (0)-Bessel Gaussian and I (0)-Bessel Gaussian beams, normalized by the rms beam wander of the fundamental Gaussian beam, is evaluated in atmospheric turbulence. Our formulation is based on the first and the second statistical moments obtained from the Rytov series. It is found that after propagating in atmospheric turbulence, the collimated J (0)-Bessel Gaussian and the I (0)-Bessel Gaussian beams have smaller rms beam wander than that of the Gaussian beam, regardless of the choice of Bessel width parameter. However, the extent of such an advantage depends on the chosen width parameter, Gaussian source size, propagation distance and the wavelength. Focusing at finite distances of the considered beams causes the rms beam wander to decrease sharply at the propagation distances equal to the focusing parameter.Article Citation - WoS: 60Citation - Scopus: 65Degree of Polarization for Partially Coherent General Beams in Turbulent Atmosphere(Springer, 2007) Eyyuboglu, H. T.; Baykal, Y.; Cai, Y.The degree of polarization is found for optical excitations of cosh-Gaussian, cos-Gaussian and annular-Gaussian beams in a turbulent atmosphere. The related formulation is based on the beam coherence polarization matrix. The self and mutual coherence functions appearing in the beam coherence polarization matrix are evaluated, when the above mentioned excitations exhibit partial source coherence for self and cross fields. Plots showing the variation of the degree of polarization are provided versus the propagation length when the source size, displacement parameter, structure constant and the degree of source coherence for self and cross fields change.Article Citation - WoS: 23Citation - Scopus: 24Annular Beam Scintillations in Non-Kolmogorov Weak Turbulence(Springer, 2012) Gercekcioglu, H.; Baykal, Y.In a weakly turbulent atmosphere governed by the non-Kolmogorov spectrum, the on-axis scintillation index is formulated and evaluated when the incidence is an annular Gaussian type. When the power law of the non-Kolmogorov spectrum is varied, the scintillation index first increases, and reaches a peak value, then starts to decrease, and eventually approaches zero. The general trend is that when turbulence has a non-Kolmogorov spectrum with power law larger than the Kolmogorov power law, the scintillation index values become smaller. For all power laws, collimated annular Gaussian beams exhibit smaller scintillations when compared to pure Gaussian beams of the same size. Intensity fluctuations at a fixed propagation distance diminish for the non-Kolmogorov spectrum with a very large power law, irrespective of the focal length and the thickness of optical annular Gaussian sources.Article Citation - WoS: 20Citation - Scopus: 21Scintillation Behavior of Laguerre Gaussian Beams in Strong Turbulence(Springer, 2011) Eyyuboglu, H. T.; Baykal, Y.; Falits, A.In strong atmospheric turbulence, the asymptotic on-axis scintillation behaviors of Laguerre Gaussian (LG) beams are examined. To arrive at the strong-turbulence solution, we utilize the existing filtering approach for weak-turbulence solutions and our recently reported weak-turbulence scintillation index formula for LG beams. In the limiting case, our solution correctly predicts the asymptotic strong-turbulence behavior of Gaussian beam wave scintillation. Investigation of the scintillations versus the propagation distance, source size, wavelength and refractive index structure parameter lead to the conclusion that the LG beams with higher order radial modes can provide less scintillation. The results are applicable to long-haul atmospheric optical communication links.Article Citation - WoS: 29Citation - Scopus: 32Intensity Fluctuations of Partially Coherent Laser Beam Arrays in Weak Atmospheric Turbulence(Springer, 2011) Arpali, C.; Arpali, S. A.; Baykal, Y.; Eyyuboglu, H. T.The intensity fluctuation of a partially coherent laser beam array is examined. For this purpose, the on-axis scintillation index at the receiver plane is analytically formulated via the extended Huygens-Fresnel diffraction integral in conditions of weak atmospheric turbulence. The effects of the propagation length, number of beamlets, radial distance, source size, wavelength of operation and coherence level on the scintillation index are investigated for a horizontal propagation path. It is found that, regardless of the number of beamlets, the scintillation index always rises with an increasing propagation length. If laser beam arrays become less coherent, the scintillation index begins to fall with growing source sizes. Given the same level of partial coherence, slightly less scintillations will occur when the radial distance of the beamlets from the origin is increased. At partial coherence levels, lower scintillations are observed for larger numbers of beamlets. Both for fully and partially coherent laser beam arrays, scintillations will drop on increasing wavelengths.Article Citation - WoS: 13Citation - Scopus: 18Partially Coherent Elegant Hermite-Gaussian Beam in Turbulent Atmosphere(Springer, 2011) Cai, Y.; Eyyuboglu, H. T.; Baykal, Y.; Wang, F.Based on the extended Huygens-Fresnel integral, analytical formulas for the cross-spectral density, mean-squared beam width and angular spread of a partially coherent elegant Hermite-Gaussian (HG) beam in turbulent atmosphere are derived. The evolution properties of the average intensity, spreading and directionality of a partially coherent elegant HG beam in turbulent atmosphere are studied numerically. It is found that the partially coherent elegant HG beam with smaller initial coherence width, larger beam order and longer wavelength is less affected by the atmospheric turbulence. Compared to the partially coherent standard HG beam, the partially coherent elegant HG beam is less affected by turbulence under the same condition. Furthermore, it is found that there exist equivalent partially coherent standard and elegant HG beams, equivalent fully coherent standard and elegant HG beams, and an equivalent Gaussian-Schell-model beam may have the same directionality as a fully coherent Gaussian beam whether in free space or in turbulent atmosphere. Our results can be utilized in short and long atmospheric optical communication systems.Article Citation - WoS: 33Citation - Scopus: 39Turbulence Distance of Radial Gaussian Schell-Model Array Beams(Springer Heidelberg, 2010) Li, X.; Ji, X.; Eyyuboglu, H. T.; Baykal, Y.The effect of turbulence on the spreading of radial Gaussian Schell-model (GSM) array beams is studied quantitatively by examining the mean-squared beam width. The analytical expression for the turbulence distance z (T) of radial GSM array beams is derived by using the integral transform technique, which indicates within what ranges radial GSM array beams will be less affected by turbulence. It is shown that the effect of turbulence on the spreading of radial GSM array beams can be reduced by choosing the suitable array beam parameters and the type of the beam superposition. In addition, a comparison with the previous work is also made.
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