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: 31Citation - Scopus: 36Beam Wander of Dark Hollow, Flat-Topped and Annular Beams(Springer Heidelberg, 2008) Cil, C. Z.; Eyyuboglu, H. T.Benefiting from the earlier derivations for the Gaussian beam, we formulate beam wander for dark hollow (DH) and flat-topped (FT) beams, also covering the annular Gaussian (AG) beam as a special case. Via graphical illustrations, beam wander variations of these beams are analyzed and compared among themselves and to the fundamental Gaussian beam against changes in propagation length, amplitude factor, source size, wavelength of operation, inner and outer scales of turbulence. These comparisons show that in relation to the fundamental Gaussian beam, DH and FT beams will exhibit less beam wander, particularly at small primary beam source sizes, lower amplitude factors of the secondary beam and higher beam orders. Furthermore, DH and FT beams will continue to preserve this advantageous position all throughout the considered range of wavelengths, inner and outer scales of turbulence. FT beams, in particular, are observed to have the smallest beam wander values among all, up to certain source sizes.Article Citation - WoS: 13Citation - Scopus: 17Correlation Properties of Random Electromagnetic Beams in Laser Resonators(Springer Heidelberg, 2009) Tong, Z.; Korotkova, O.; Cai, Y.; Eyyuboglu, H. T.; Baykal, Y.With the help of the generalized Huygens-Fresnel principle and the tensor approach for electromagnetic stochastic beams we investigate the behavior of their two-point spatial correlation properties on interaction with a laser resonator. In particular, the evolution of the degree of coherence, of the degree of cross-polarization and of the intensity correlations (at one and two points in space) is analyzed for typical beams and cavities. The theory is illustrated by numerical curves pertaining to various correlation properties of typical electromagnetic Gaussian Schell-model beams.Article Citation - WoS: 7Citation - Scopus: 8Fringe Waves Radiated by a Half-Plane for the Boundary Conditions of Neumann(Springer Heidelberg, 2008) Umul, Y. Z.The fringe waves of the physical theory of diffraction are obtained in terms of Fresnel integrals for a half-plane satisfying the Neumann boundary condition. The approximate expressions of the radiated waves are also evaluated for sufficiently large wavenumbers. The fields are plotted and compared numerically.Article Citation - WoS: 76Citation - Scopus: 82Scintillation Properties of Dark Hollow Beams in a Weak Turbulent Atmosphere(Springer Heidelberg, 2008) Chen, Y.; Cai, Y.; Eyyuboglu, H. T.; Baykal, Y.The on-axis scintillation index for a circular dark hollow beam (DHB) propagating in a weak turbulent atmosphere is formulated, and the scintillation properties of a DHB are investigated in detail. The scintillation index for a DHB reduces to the scintillation index for a Gaussian beam, an annular beam and a flat-topped beam under certain conditions. It is found that the scintillation index of a DHB is closely related to the beam parameters and can be lower than that of a Gaussian beam, an annular beam and a flat-topped beam in a weak turbulent atmosphere at smaller waist sizes and longer propagation lengths.Article Citation - WoS: 85Citation - Scopus: 88Scintillations of Laser Array Beams(Springer Heidelberg, 2008) Eyyuboglu, H. T.; Baykal, Y.; Cai, Y.The scintillation index of a laser array beam is analytically derived and numerically evaluated for weak turbulence conditions. On-axis as well as off-axis positions of the receiver plane are considered. Our graphical illustrations prove that at longer propagation ranges and at some midrange radial displacement parameters, laser array beams exhibit less scintillations, when compared to a fundamental Gaussian beam. However, when compared among themselves, laser array beams tend to have reduced scintillations with rising numbers of beamlets, longer propagation wavelengths, at midrange radial displacement parameters, at intermediate Gaussian source sizes, at bigger inner scales and smaller outer scales of turbulence. However, in this improvement, the number of beamlets does not seem to have a major role.Article Citation - WoS: 36Citation - Scopus: 38Scintillation Advantages of Lowest Order Bessel-Gaussian Beams(Springer Heidelberg, 2008) Baykal, Y.; Sermutlu, E.; Cai, Y.; Eyyuboglu, H. T.For a weak turbulence propagation environment, the scintillation index of the lowest order Bessel-Gaussian beams is formulated. Its triple and single integral versions are presented. Numerical evaluations show that at large source sizes and large width parameters, when compared at the same source size, Bessel-Gaussian beams tend to exhibit lower scintillations than the Gaussian beam scintillations. This advantage is lost however for excessively large width parameters and beyond certain propagation lengths. Large width parameters also cause rises and falls in the scintillation index of off-axis positions toward the edges of the received beam. Comparisons against the fundamental Gaussian beam are made on equal source size and equal power basis.Article Citation - WoS: 132Citation - Scopus: 153Propagation of Laser Array Beams in a Turbulent Atmosphere(Springer Heidelberg, 2007) Cai, Y.; Chen, Y.; Eyyuboglu, H. T.; Baykal, Y.The propagation of phase-locked and non-phase-locked laser array beams of radial and rectangular symmetries in a turbulent atmosphere are investigated based on the extended Huygens-Fresnel integral. The beamlet used in our paper for constructing the laser array beams is of elliptical Gaussian mode. Analytical formulae for the average irradiance of phase-locked and non-phase-locked radial and rectangular laser array beams are derived through vector integration and tensor operation. The irradiance properties of these laser array beams in a turbulent atmosphere are studied numerically. It is found that both phase-locked and non-phase-locked radial and rectangular laser array beams eventually become circular Gaussian beams in a turbulent atmosphere, which is much different from their propagation properties in free space. The propagation properties are closely related to the parameters of laser array beams and the structure constant of the turbulent atmosphere.