Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Conference Object Propagation of Partially Coherent Beams After a Source Plane Ring Aperture(Electromagnetics Acad, 2008) Eyyuboğlu, Halil Tanyer; Eyyuboglu, H. T.; Baykal, Yahya Kemal; Baykal, Y. K.; Cai, Y.; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik MühendisliğiThe propagation properties of partially coherent beams passing through a source placed ring aperture are examined. The derivation is based on the lowest order general beam formulation, such that our results are applicable to a wide range of beam. In this study, our focus is on fundamental Gaussian, cosh-Gaussian, cos-Gaussian, sinh-Gaussian, sine-Gaussian and annular beams. The aperture consists of inner and outer parts, thus the middle hollow part appears in the form of a ring. The propagation environment is turbulent. From the graphical outputs of the beams investigated, it is seen that despite the existence of the circular ring, during propagation, the beams tend to retain the basic profiles similar to the case of no aperture, but depending on the inner and outer radius dimensions, the propagated beams are reduced in intensity levels and become more spread. It is further observed that, when the inner part of the aperture has nonzero radius, ring formations are developed at the outer edges of the receiver plane intensities.Conference Object Citation - WoS: 1Citation - Scopus: 1Scintillations in Weak Turbulence of Annular Beams Whose Individual Components Are Incoherent(Electromagnetics Acad, 2010) Eyyuboğlu, Halil Tanyer; Baykal, Y.; Eyyuboglu, H. T.; Baykal, Yahya Kemal; Cai, Y.; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik MühendisliğiThe scintillation index, arising from the intensity fluctuations in weak atmospheric turbulence of annular beams whose individual components are incoherent, is formulated. For such beams whose annularities are obtained by varying the source sizes and magnitudes of the individual beams, evaluations show that at very small sized beam structures, thinner beams possess smaller scintillations. As the sizes increase, the scintillation index values of thick and thin beams approach each other, eventually exhibiting the same scintillation behavior at large sized beam structures. Examination of the intensity fluctuations of the annular beams, whose individual incoherent components are at the same size but at different magnitudes, yield reverse behavior such that at very small sized beam structures, thicker beams possess smaller scintillations, however the scintillation values are very close to each other. Again, for large sized beams, the scintillation index values of thick and thin beams approach each other, eventually exhibiting the same scintillation behavior at large sized beam structures. Comparing the scintillation indices of annular beams whose individual components are incoherent to those of traditional annular beams of coherent components, it seems that for large sized beams, incoherently subtracted beams are advantageous, however the reverse is valid for very small sized beam structures.Conference Object Citation - WoS: 1Formulation of Scintillations for Optical Incidence of Arbitrary Field Profile(Electromagnetics Acad, 2008) Eyyuboğlu, Halil Tanyer; Baykal, Y.; Eyyuboglu, H. T.; Baykal, Yahya Kemal; Cai, Y.; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik MühendisliğiScintillation index on the receiver axis is formulated in random medium when an optical source with an arbitrary field profile is employed. To represent the arbitrary source field profile, source is decomposed into pixels and the incident field to form the scintillations is expressed as the superposition of the fields from each pixel area. Thus obtained arbitrary field distribution is then introduced into the weak atmospheric turbulence formulation by using Rytov method. Our result, which is in summa ion and integral forms, reduces correctly to the known scintillation index of a Gaussian beam wave in atmospheric turbulence.