WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Article Citation - WoS: 183Citation - Scopus: 193Analysis of Reciprocity of Cos-Gaussian and Cosh-Gaussian Laser Beams in a Turbulent Atmosphere(Optical Soc Amer, 2004) Eyyuboglu, HT; Baykal, YIn a turbulent atmosphere, starting with a cos-Gaussian excitation at the source plane, the average intensity profile at the receiver plane is formulated. This average intensity profile is evaluated against the variations of link lengths, turbulence levels, two frequently used free-space optics wavelengths, and beam displacement parameters. We show that a cos-Gaussian beam, following a natural diffraction, is eventually transformed into a cosh-Gaussian beam. Combining our earlier results with the current findings, we conclude that cos-Gaussian and cosh-Gaussian beams act in a reciprocal manner after propagation in turbulence. The rates (paces) of conversion in the two directions are not the same. Although the conversion of cos-Gaussian beams to cosh-Gaussian beams can happen over a wide range of turbulence levels (low to moderate to high), the conversion of cosh-Gaussian beams to cos-Gaussian beams is pronounced under relatively stronger turbulence conditions. Source and propagation parameters that affect this reciprocity have been analyzed. (C) 2004 Optical Society of America.Article Citation - WoS: 88Citation - Scopus: 87Correlation and Structure Functions of Hermite-Sinusoidal Laser Beams in a Turbulent Atmosphere(Optical Soc Amer, 2004) Baykal, YTo study the performance of atmospheric optical links by using Hermite-sinusoidal-Gaussian laser beam sources, we derive the log-amplitude and the phase correlation and structure functions of such beams in a turbulent atmosphere. Our formulations correctly reduce to the known higher-order mode correlation and structure functions, which in turn reduce to the fundamental-mode (TEM00-mode) results. Several special cases of our formulation are presented, among which the case involving Hermite-cosh-Gaussian dependence is especially noted, since this case is of interest to us owing to the nature of cosh dependence exhibiting the concentration of the energy in the outer lobes of the beam. (C) 2004 Optical Society of America.Article Citation - WoS: 127Citation - Scopus: 135Average Intensity and Spreading of Cosh-Gaussian Laser Beams in the Turbulent Atmosphere(Optical Soc Amer, 2005) Eyyuboglu, HT; Baykal, YThe average intensity and spreading of cosh-Gaussian laser beams in the turbulent atmosphere are examined. Our research is based principally on formulating the average-intensity profile at the receiver plane for cosh-Gaussian excitation. The limiting cases of our formulation for the average intensity are found to reduce correctly to the existing Gaussian beam wave result in turbulence and the cosh-Gaussian beam result in free space (in the absence of turbulence). The average intensity and the broadening of the cosh-Gaussian beam wave after it propagates in the turbulent atmosphere are numerically evaluated versus source size, beam displacement, link length, structure constant, and two wavelengths of 0.85 and 1.55 mum, which are most widely used in currently employed free-space-optical links. Results indicate that in turbulence the beam is widened beyond its free-space diffraction values. At the receiver plane, analogous to the case of free space, this diffraction eventually leads to transformation of the cosh-Gaussian beam into an oscillatory average-intensity profile with a Gaussian envelope. (C) 2005 Optical Society of America.Article Citation - WoS: 48Citation - Scopus: 55Log-Amplitude and Phase Fluctuations of Higher-Order Annular Laser Beams in a Turbulent Medium(Optical Soc Amer, 2005) Baykal, YLog-amplitude and phase-correlation and structure functions of higher-order annular laser beams in a turbulent atmosphere are derived. A higher-order annular beam source is defined as the superposition of two different higher-order Hermite-Gaussian beams. A special case of such an excitation is the annular Gaussian beam in which two beams operate at fundamental modes of different Gaussian beam sizes, yielding a doughnut-shaped (annular) beam when the second beam is subtracted from the first beam. Our formulation utilizes Rytov approximation, which makes it applicable in the weak-turbulence regime, especially for log-amplitude fluctuations. Limiting cases of our formulations correctly match with known higher-order-mode solutions that in turn reduce to the Gaussian-beam-wave (TEM00-mode) results. Our results can be applied to determine the scintillation index and the phase fluctuations in free-space optics links under higher-order annular laser beam excitation. Except for the numerical evaluation of a specific example covering an annular Gaussian beam, the results in general are left in integral form and need to be numerically evaluated in detail to obtain quantitative results. (c) 2005 Optical Society of America.Article Citation - WoS: 62Citation - Scopus: 72Hermite-Sine and Hermite-Sinh Laser Beams in Turbulent Atmosphere(Optical Soc Amer, 2005) Eyyuboglu, HT; Baykal, YHermite-sine-Gaussian and Hermite-sinh-Gaussian laser beam intensities in a turbulent atmosphere are investigated. The received intensity is formulated by applying the extended Huygens-Fresnel principle to generalized Hermite-hyperbolic-Gaussian and Hermite-sinusoidal-Gaussian beam incidences. From this result, the association to different types of Hermite-hyperbolic-Gaussian and Hermite-sinusoidal-Gaussian beams are defined. The average receiver intensity expressions for Hermite-sine-Gaussian and Hermite-sinh-Gaussian laser beams are evaluated and plotted against the variations in source parameters and propagation conditions. It is observed that the propagation of Hermite-sine-Gaussian and Hermite-sinh-Gaussian laser beams in turbulence have many similarities to their counterparts, Hermite-cosine-Gaussian and Hermite-cosh-Gaussian laser beams, that are examined earlier. It is further observed that under certain conditions the main features of the previously established reciprocity concept between cosine-Gaussian and cosh-Gaussian beams are mostly applicable to Hermite-sine-Gaussian and Hermite-sinh-Gaussian laser beams. (c) 2005 Optical Society of America.Article Citation - WoS: 104Citation - Scopus: 104Formulation of Correlations for General-Type Beams in Atmospheric Turbulence(Optical Soc Amer, 2006) Baykal, YLog-amplitude and phase correlations of general-type beams are formulated in atmospheric turbulence. A general beam is described as the superposition of many sets of multimode contents, each mode being off-axis Hermite-Gaussian. Since the Rytov solution is utilized, the formulas are valid in the weakly turbulent regime. The results are presented in integral forms that should be numerically evaluated for the specific beam type of interest. Our general beam results correctly reduce to the existing solutions for the correlations of limiting-case beams such as higher-order single-mode, multimode, off-axis Hermite-Gaussian, Hermite-sinusoidal-Gaussian, higher-order-annular, flat-topped-Gaussian, and thus naturally fundamental mode, plane, and spherical waves. Scintillation index and phase fluctuations in atmospheric optical links employing such special beams will be examined in future using the results reported here. (c) 2006 Optical Society of America.