WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Article Citation - WoS: 16Citation - Scopus: 18Adaptive Optics Correction of Scintillation in Underwater Medium(Taylor & Francis Ltd, 2020) Baykal, YahyaAdaptive optics correction of the scintillation index of a Gaussian laser beam in underwater turbulence is studied. To introduce the adaptive optics correction, filter functions providing the piston, tilt and astigmatism effects are adapted to promote the spectrum of underwater turbulence. The reduction of the scintillation index due to the individual piston, tilt, astigmatism effects and their sum is examined versus the ratio of temperature to salinity contributions to the refractive index spectrum, the rate of dissipation of mean squared temperature, the rate of dissipation of kinetic energy per unit mass of fluid, receiving aperture diameter, source size, link length and the wavelength. For any value of underwater turbulence parameter, the most effective adaptive optics corrections are found to be the piston, tilt and astigmatism, respectively.Article Citation - WoS: 15Citation - Scopus: 16Scintillation Behaviour of Vortex Beams in Strong Turbulence Region(Taylor & Francis Ltd, 2016) Eyyuboglu, H. T.We study the scintillation behaviour of vectorial vortex beams in strong turbulence region. For this purpose, a list of vortex source beams is prepared. Then their scintillation performances are analysed one by one using the random phase screen approach. The results indicate that there will always be scintillation reductions with increasing values of topological charge, although its effect will diminish as we go towards higher values of the topological charge. The increases in the other specific beam parameters seem to have opposite effect. For the vectorial Hermite Gaussian beam, the use of higher orders will also aid scintillation reductions. It is foreseen that the outcome of this study will be useful for long haul optical communication links.Article Citation - WoS: 27Citation - Scopus: 28Analysis of Flat-Topped Gaussian Vortex Beam Scintillation Properties in Atmospheric Turbulence(Spie-soc Photo-optical instrumentation Engineers, 2019) Elmabruk, Kholoud; Eyyuboglu, Halil T.We analyze the scintillation properties of a flat-topped Gaussian vortex beam propagating in a weakly turbulent atmosphere. We utilize a random phase screen model to perform this analysis. We evaluate the scintillation against the changes of topological charge, beam order, operating wavelength, receiver aperture side length, and source size parameters. The results show that using a flat-topped Gaussian vortex beam with a high topological charge causes a reduction in scintillation. Increasing the receiver aperture side length reduces scintillation level. As the source size increases, scintillation decreases. Our results also indicate that a flat-topped Gaussian vortex beam with high topological charges has less scintillation than the fundamental Gaussian beam. We believe that our findings will be useful in improving the performance of next-generation optical communication links and networks. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)Article Citation - WoS: 4Citation - Scopus: 4The Analysis of Anisotropic the Non-Kolmogorov Turbulence Effect on Asymmetrical Gaussian Beam Propagation in a Marine Atmosphere(Iop Publishing Ltd, 2019) Ata, Yalcin; Baykal, YahyaThe variations of the scintillation index of an asymmetrical Gaussian beam are investigated when the beam propagates in anisotropic non-Kolmogorov marine atmospheric turbulence. The results indicate that the scintillation decreases when the anisotropy factors in both x and y directions increase. Increases in the beam asymmetry ratio and the inner scale length increase the scintillation index level. The scintillations are found to increase as the propagation distance and structure constant increase, and as the wavelength decreases. Being valid for any asymmetry and anisotropic factor, for small values of the power law exponent, alpha of non-Kolmogorov marine atmospheric turbulence, the scintillation index tends to increase proportionally with alpha. However, as alpha is further increased, the scintillation index starts to decrease after reaching a peak value. Larger anisotropy in the non-Kolmogorov marine turbulence is found to be preferable since the scintillation index is found to decrease at large anisotropic factors.Article Citation - WoS: 10Citation - Scopus: 10Cross-Beam Scintillations in Underwater Medium(Spie-soc Photo-optical instrumentation Engineers, 2016) Baykal, YahyaThe fluctuation in the intensity, which is quantified by the scintillation index, is evaluated for cross beams when such beams propagate in an underwater medium experiencing turbulence. The variations in the scintillation index are investigated against the changes in the size of the cross beams, the ratio of temperature to salinity contributions to the refractive index spectrum, the rate of dissipation of mean-squared temperature, and the rate of dissipation of kinetic energy per unit mass of fluid. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)Article Citation - WoS: 11Citation - Scopus: 10Receiver-Aperture Averaging of Annular Beams Propagating Through Turbulent Atmosphere(Spie-soc Photo-optical instrumentation Engineers, 2013) Kamacioglu, Canan; Baykal, Yahya; Yazgan, ErdemFor an annular beam incidence, the power scintillation index in a weakly turbulent atmosphere is derived at the receiver plane, which has a Gaussian aperture. Employing this derivation, the receiver-aperture averaging factor is evaluated. Annular beams are found more advantageous than the Gaussian beams when compared on receiver-aperture averaging basis. The analyses indicate that the effect of the aperture averaging increases as the propagation length increases. Increase in the structure constant and the secondary beam source size is observed to strengthen the effect of the aperture averaging when the primary beam source size is fixed. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)Article Citation - WoS: 20Snr Bounds of Fso Links and Its Evaluation for Selected Beams(Taylor & Francis Ltd, 2015) Bayraktar, Mert; Eyyuboglu, Halil T.We formulate the signal-to-noise ratio (SNR) for free-space optical links. Upon inserting typical operating parameters, it is seen that SNR well approximates to the inverse of aperture averaged scintillation parameter. By adopting a common source beam power of 10 mW, we select three different source sizes of Gaussian, annular Gaussian (AG), and cosh-Gaussian beams. We then evaluate the SNR of these beams. Our results indicate that when fixed aperture opening is used, fully and partially coherent beams yield almost the same SNR performance. On the other hand, however, focusing and lowering wavelength of operation appear to be quite instrumental in improving the SNR performance. In this context, medium-sized AGB seems to exhibit the best performance.