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: 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: 37Citation - Scopus: 38Diffraction by a Black Half Plane: Modified Theory of Physical Optics Approach(Optical Soc Amer, 2005) Umul, YZThe scattered fields from a black half plane which absorbs all the incoming electromagnetic energy are evaluated by defining a new modified theory of physical optics surface current. This current eliminates the reflected fields, coming from the first stationary point of the reflection integral and only creates a reflected diffracted field. The incident scattered fields are found from the same integral, written for the perfectly conducting half plane. The scattered fields are evaluated by using the stationary phase method and edge point technique. The evaluated fields are plotted numerically. (c) 2005 Optical Society of America.Article Citation - WoS: 67Citation - Scopus: 67Equivalent Functions for the Fresnel Integral(Optical Soc Amer, 2005) Umul, YZFresnel integral is modeled with three equivalent functions. The first function is derived by considering the sum of the first term of the Fresnel integral's asymptotic expansion {(F) over cap (x)} and an exponential function which approaches to infinity at the zero of the Fresnel function's argument and has the properties of a unit step function. The second one is the sum of a unit step function and the transition function defined for the simplified uniform theory of diffraction. The third function considers directly eliminating the infinity coming from (F) over cap (x). The amplitude and the phase of Fresnel integral and its equivalent functions are compared numerically. The result is applied to the modified theory of physical optics solution of the diffraction of edge waves from a half plane problem. (c) 2005 Optical Society of America.Article Citation - WoS: 80Citation - Scopus: 85Propagation of an Airy Beam Through the Atmosphere(Optical Soc Amer, 2013) Ji, Xiaoling; Eyyuboglu, Halil T.; Ji, Guangming; Jia, XinhongIn this paper, the effect of thermal blooming of an Airy beam propagating through the atmosphere is examined, and the effect of atmospheric turbulence is not considered. The changes of the intensity distribution, the centroid position and the mean-squared beam width of an Airy beam propagating through the atmosphere are studied by using the four-dimensional (4D) computer code of the time-dependent propagation of Airy beams through the atmosphere. It is shown that an Airy beam can't retain its shape and the structure when the Airy beam propagates through the atmosphere due to thermal blooming except for the short propagation distance, or the short time, or the low beam power. The thermal blooming results in a central dip of the center lobe, and causes the center lobe to spread and decrease. In contrast with the center lobe, the side lobes are less affected by thermal blooming, such that the intensity maximum of the side lobe may be larger than that of the center lobe. However, the cross wind can reduce the effect of thermal blooming. When there exists the cross wind velocity v(x) in x direction, the dependence of centroid position in x direction on v(x) is not monotonic, and there exists a minimum, but the centroid position in y direction is nearly independent of v(x). (C) 2013 Optical Society of AmericaArticle Citation - WoS: 67Influence of Turbulence on the Effective Radius of Curvature of Radial Gaussian Array Beams(Optical Soc Amer, 2010) Ji, Xiaoling; Eyyuboglu, Halil T.; Baykal, YahyaThe analytical formula for the effective radius of curvature of radial Gaussian array beams propagating through atmospheric turbulence is derived, where coherent and incoherent beam combinations are considered. The influence of turbulence on the effective radius of curvature of radial Gaussian array beams is studied by using numerical calculation examples. (C) 2010 Optical Society of AmericaArticle Citation - WoS: 136Citation - Scopus: 148M<sup>2</Sup>-factor of Coherent and Partially Coherent Dark Hollow Beams Propagating in Turbulent Atmosphere(Optical Soc Amer, 2009) Yuan, Yangsheng; Cai, Yangjian; Qu, Jun; Eyyuboglu, Halil T.; Bayka, Yahya; Korotkova, Olga; Baykal, YahyaAnalytical formula is derived for the M-2-factor of coherent and partially coherent dark hollow beams (DHB) in turbulent atmosphere based on the extended Huygens-Fresnel integral and the second-order moments of the Wigner distribution function. Our numerical results show that the M-2-factor of a DHB in turbulent atmosphere increases on propagation, which is much different from its invariant properties in free-space, and is mainly determined by the parameters of the beam and the atmosphere. The relative M-2-factor of a DHB increases slower than that of Gaussian and flat-topped beams on propagation, which means a DHB is less affected by the atmospheric turbulence than Gaussian and flat-topped beams. Furthermore, the relative M-2-factor of a DHB with lower coherence, longer wavelength and larger dark size is less affected by the atmospheric turbulence. Our results will be useful in long-distance free-space optical communications. (C) 2009 Optical Society of AmericaArticle Citation - WoS: 53Citation - Scopus: 58Average Intensity and Spreading of an Elegant Hermite-Gaussian Beam in Turbulent Atmosphere(Optical Soc Amer, 2009) Yuan, Yangsheng; Cai, Yangjian; Qu, Jun; Eyyuboglu, Halil T.; Baykal, YahyaThe propagation of an elegant Hermite-Gaussian beam (EHGB) in turbulent atmosphere is investigated. Analytical propagation formulae for the average intensity and effective beam size of an EHGB in turbulent atmosphere are derived based on the extended Huygens-Fresnel integral. The corresponding results of a standard Hermite-Gaussian beam (SHGB) in turbulent atmosphere are also derived for the convenience of comparison. The intensity and spreading properties of EHGBs and SHGBs in turbulent atmosphere are studied numerically and comparatively. It is found that the propagation properties of EHGBs and SHGBs are much different from their properties in free space, and the EHGB and SHGB with higher orders are less affected by the turbulence. What's more, the SHGB spreads more rapidly than the EHGB in turbulent atmosphere under the same conditions. Our results will be useful in long-distance free-space optical communications. (C) 2009 Optical Society of AmericaArticle Citation - WoS: 113Citation - Scopus: 123Radiation Force of Coherent and Partially Coherent Flat-Topped Beams on a Rayleigh Particle(Optical Soc Amer, 2009) Zhao, Chengliang; Cai, Yangjian; Lu, Xuanhui; Eyyuboglu, Halil T.Propagations of coherent and partially coherent flat-topped beams through a focusing optical system are formulated. The radiation force on a Rayleigh dielectric sphere induced by focused coherent and partially coherent flat-topped beams is investigated theoretically. It is found that we can increase the transverse trapping range at the planes near the focal plane by increasing the flatness (i.e., beam order) of the flat-topped beam, and increase the transverse and longitudinal trapping ranges at the focal plane by decreasing the initial coherence of the flat-topped beam. Moreover the trapping stiffness of flat-topped beam becomes lower as the beam order increases or the initial coherence decreases. The trapping stability is also analyzed. (C) 2009 Optical Society of AmericaArticle Citation - WoS: 115Citation - Scopus: 118Average Irradiance and Polarization Properties of a Radially or Azimuthally Polarized Beam in a Turbulent Atmosphere(Optical Soc Amer, 2008) Cai, Yangjian; Lin, Qiang; Eyyuboglu, Halil T.; Baykal, YahyaAnalytical formulas are derived for the average irradiance and the degree of polarization of a radially or azimuthally polarized doughnut beam (PDB) propagating in a turbulent atmosphere by adopting a beam coherence-polarization matrix. It is found that the radial or azimuthal polarization structure of a radially or azimuthally PDB will be destroyed (i.e., a radially or azimuthally PDB is depolarized and becomes a partially polarized beam) and the doughnut beam spot becomes a circularly Gaussian beam spot during propagation in a turbulent atmosphere. The propagation properties are closely related to the parameters of the beam and the structure constant of the atmospheric turbulence. (C) 2008 Optical Society of America.Article Citation - WoS: 138Citation - Scopus: 137Flat Topped Beams and Their Characteristics in Turbulent Media(Optical Soc Amer, 2006) Eyyuboglu, Halil Tanyer; Arpali, Caglar; Baykal, Yahya KemalThe source and receiver plane characteristics of flat topped ( FT) beam propagating in turbulent atmosphere are investigated. To this end, source size, beam power and M(2) factor of source plane FT beam are derived. For a turbulent propagation medium, via Huygens Fresnel diffraction integral, the receiver plane intensity is found. Power captured within an area on the receiver plane is calculated. Kurtosis parameter and beam size variation along the propagation axis are formulated. Graphical outputs are provided displaying the variations of the derived source and receiver plane parameters against the order of flatness and propagation length. Analogous to free space behavior, when propagating in turbulence, the FT beam first will form a circular ring in the center. As the propagation length increases, the circumference of this ring will become narrower, giving rise to a downward peak emerging from the center of the beam, eventually turning the intensity profile into a pure Gaussian shape. (c) 2006 Optical Society of America.