Browsing by Author "Cil, C. Z."

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Citation - WoS: 26
Citation - Scopus: 26
Beam wander characteristics of cos and cosh-Gaussian beams
(Springer, 2009) Cil, C. Z.; Çil, Celal Zaim; Eyyuboglu, H. T.; Baykal, Y.; Cai, Y.; 7688; 7812; Elektronik ve Haberleşme Mühendisliği
Within the context of a general beam formulation, beam wander characteristics of cos and cosh-Gaussian beams are derived and numerically evaluated. In our graphs, the fundamental Gaussian beam is used as a benchmark for comparisons. The associated plots reveal that at small source sizes, a cos-Gaussian beam has the lowest beam wander, while this property is enhanced with increasing values of the displacement parameter. At large source sizes however, this advantage is taken over by cosh-Gaussian beam. Joint examination against the changing source sizes and propagation lengths shows that the range of source sizes, where the beam wander of cos-Gaussian beam remains lower, is enlarged as we go toward higher propagation lengths. Asymmetric beams tend to exhibit higher beam wanders both at small and large source sizes, but for the intermediate source size ranges, the beam wanders of asymmetric beams will fall below those of the symmetric beams. Explanations concerning these behaviors are offered. A historical account of beam wander formulation is also included.
Citation - WoS: 30
Citation - Scopus: 35
Beam wander of dark hollow, flat-topped and annular beams
(Springer Heidelberg, 2008) Eyyuboglu, H. T.; Çil, Celal Zaim; Cil, C. Z.; 7688; Elektronik ve Haberleşme Mühendisliği
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.
Citation - WoS: 26
Citation - Scopus: 27
Beam Wander of J (0)- and I (0)-Bessel Gaussian Beams Propagating In Turbulent Atmosphere
(Springer, 2010) Cil, C. Z.; Çil, Celal Zaim; Eyyuboglu, H. T.; Baykal, Y.; Korotkova, O.; Cai, Y.; 7812; 7688; Elektronik ve Haberleşme Mühendisliği
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.
Citation - WoS: 12
Citation - Scopus: 14
Partially coherent elegant Hermite-Gaussian beams
(Springer Heidelberg, 2010) Wang, F.; Çil, Celal Zaim; Cai, Y.; Eyyuboglu, H. T.; Baykal, Y.; Cil, C. Z.; 7688; 7812; Elektronik ve Haberleşme Mühendisliği
Elegant Hermite-Gaussian beams (EHGBs) are extended to the partially coherent case. An explicit and analytical formula is derived for the cross-spectral density of a partially coherent EHGB propagating through an aligned or misaligned paraxial ABCD optical system. The propagation properties of a partially coherent EHGB in free space and its focusing properties through a thin lens are studied numerically, and are compared to those of a partially coherent standard Hermite-Gaussian beam (SHGB). It is found that the propagation and focusing properties of a partially coherent EHGB are closely related to its initial coherence. A partially coherent EHGB spreads slower than a partially coherent SHGB in free-space propagation. A partially coherent EHGB can be focused more tightly than a partially coherent SHGB.