Prof. Yahya Kemal Baykal Profile

Prof. Yahya Kemal Baykal

Vice Rector at Cankaya Univ

SPIE Involvement:

Conference Program Committee | Author

Area of Expertise:

Atmospheric turbulence , Telecommunication networks , Free space optics systems

Websites:

Company Website

Publications (26)

SPIE Journal Paper | May 30, 2018

Bit-error-rate performance of optical wireless system using higher order mode laser in anisotropic non-Kolmogorov turbulence

Ata, Yalçın , Baykal, Yahya

OE Vol. 57 Issue 05

KEYWORDS: Turbulence, Atmospheric optics, Atmospheric propagation, Anisotropy, Signal to noise ratio, Atmospheric turbulence, Laser beam propagation, Gaussian beams, Optical engineering, Wave propagation

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SPIE Journal Paper | October 16, 2017

Flat-topped beam transmittance in anisotropic non-Kolmogorov turbulent marine atmosphere

Ata, Yalçın , Baykal, Yahya

OE Vol. 56 Issue 10

KEYWORDS: Transmittance, Ocean optics, Atmospheric optics, Turbulence, Anisotropy, Wave propagation, Atmospheric propagation, Atmospheric propagation engineering, Receivers, Atmospheric turbulence

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SPIE Journal Paper | September 21, 2016

Cross-beam scintillations in underwater medium

Baykal, Yahya

OE Vol. 55 Issue 11

KEYWORDS: Scintillation, Turbulence, Gaussian beams, Refractive index, Ocean optics, Atmospheric turbulence, Atrial fibrillation, Water, Atmospheric propagation, Wireless communications

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SPIE Journal Paper | August 10, 2016

Performance analysis of multiple-input multiple-output free-space optical systems with partially coherent Gaussian beams and finite-sized detectors

Gökçe, Muhsin , Baykal, Yahya , Uysal, Murat

OE Vol. 55 Issue 11

KEYWORDS: Receivers, Scintillation, Free space optics, Transmitters, Gaussian beams, Signal to noise ratio, Sensors, Beam shaping, Atmospheric turbulence, Optical engineering

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SPIE Journal Paper | June 25, 2015

Aperture averaging in multiple-input single-output free-space optical systems

Gökçe, Muhsin , Baykal, Yahya , Kamacioğlu, Canan , Uysal, Murat

OE Vol. 54 Issue 06

KEYWORDS: Scintillation, Receivers, Free space optics, Transmitters, Gaussian beams, Atmospheric turbulence, Optical engineering, Wave propagation, Turbulence, Telecommunications

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PROCEEDINGS ARTICLE | October 3, 2014

Performance analysis of MIMO FSO systems with radial array beams and finite sized detectors

Proc. SPIE. 9224, Laser Communication and Propagation through the Atmosphere and Oceans III

KEYWORDS: Transmitters, Gaussian beams, Sensors, Receivers, Wave propagation, Telecommunications, Free space optics, Scintillation, Atmospheric turbulence, Electronics engineering

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SPIE Journal Paper | May 12, 2014

Crossbeam intensity fluctuations in turbulence

Baykal, Yahya

OE Vol. 53 Issue 05

KEYWORDS: Gaussian beams, Collimation, Scintillation, Atrial fibrillation, Turbulence, Atmospheric optics, Atmospheric propagation, Atmospheric turbulence, Optical engineering, Communication engineering

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SPIE Journal Paper | December 16, 2013

Receiver-aperture averaging of annular beams propagating through turbulent atmosphere

Kamacioglu, Canan , Baykal, Yahya , Yazgan, Erde,

OE Vol. 52 Issue 12

KEYWORDS: Scintillation, Atmospheric propagation, Receivers, Gaussian beams, Beam propagation method, Atmospheric propagation engineering, Atmospheric scintillation, Wave propagation, Optical engineering, Atmospheric optics

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PROCEEDINGS ARTICLE | February 10, 2011

Method of evaluation of the mutual coherence function of laser beams and its application for symmetric dark hollow beams

Proc. SPIE. 7924, Atmospheric and Oceanic Propagation of Electromagnetic Waves V

KEYWORDS: Refractive index, Coherence (optics), Ocean optics, Wave propagation, Turbulence, Spherical lenses, Atmospheric propagation, Beam propagation method, Atmospheric optics, Radio propagation

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PROCEEDINGS ARTICLE | February 27, 2010

Propagation of elegant higher-order Gaussian beams in turbulent atmosphere

Proc. SPIE. 7588, Atmospheric and Oceanic Propagation of Electromagnetic Waves IV

KEYWORDS: Gaussian beams, Atmospheric laser remote sensing, Atmospheric propagation engineering, Free space, Laser beam propagation, Wave propagation, Turbulence, Atmospheric propagation, Beam propagation method, Radio propagation

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PROCEEDINGS ARTICLE | February 27, 2010

Intensity fluctuations of incoherently superposed Gaussian beams in atmospheric turbulence

Proc. SPIE. 7588, Atmospheric and Oceanic Propagation of Electromagnetic Waves IV

KEYWORDS: Superposition, Gaussian beams, Wave propagation, Turbulence, Scintillation, Atmospheric turbulence, Atmospheric propagation, Atmospheric scintillation, Atmospheric optics, Radio propagation

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PROCEEDINGS ARTICLE | February 27, 2010

Beam wander characteristics of flat-topped, dark hollow, cos and cosh-Gaussian, J0- and I0- Bessel Gaussian beams propagating in turbulent atmosphere: a review

Proc. SPIE. 7588, Atmospheric and Oceanic Propagation of Electromagnetic Waves IV

KEYWORDS: Gaussian beams, Fourier transforms, Receivers, Turbulence, Free space optics, Scintillation, Atmospheric turbulence, Atmospheric propagation, Beam propagation method, Beam analyzers

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PROCEEDINGS ARTICLE | February 24, 2009

Average received intensity for optical beam of arbitrary field profile after propagation in turbulent atmosphere

Proc. SPIE. 7200, Atmospheric Propagation of Electromagnetic Waves III

KEYWORDS: Receivers, Wave propagation, Telecommunications, Turbulence, Beam shaping, Atmospheric turbulence, Atmospheric propagation, Beam propagation method, Atmospheric optics, Radio propagation

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PROCEEDINGS ARTICLE | February 13, 2009

Effect of beam types on the scintillations: a review

Proc. SPIE. 7200, Atmospheric Propagation of Electromagnetic Waves III

KEYWORDS: Monochromatic aberrations, Gaussian beams, Receivers, Laser beam propagation, Turbulence, Scintillation, Atmospheric propagation, Beam propagation method, Atmospheric scintillation, Atmospheric optics

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When different incidences are launched in atmospheric turbulence, it is known that the intensity fluctuations exhibit different characteristics. In this paper we review our work done in the evaluations of the scintillation index of general beam types when such optical beams propagate in horizontal atmospheric links in the weak fluctuations regime. Variation of scintillation indices versus the source and medium parameters are examined for flat-topped-Gaussian, cosh- Gaussian, cos-Gaussian, annular, elliptical Gaussian, circular (i.e., stigmatic) and elliptical (i.e., astigmatic) dark hollow, lowest order Bessel-Gaussian and laser array beams. For flat-topped-Gaussian beam, scintillation is larger than the single Gaussian beam scintillation, when the source sizes are much less than the Fresnel zone but becomes smaller for source sizes much larger than the Fresnel zone. Cosh-Gaussian beam has lower on-axis scintillations at smaller source sizes and longer propagation distances as compared to Gaussian beams where focusing imposes more reduction on the cosh- Gaussian beam scintillations than that of the Gaussian beam. Intensity fluctuations of a cos-Gaussian beam show favorable behaviour against a Gaussian beam at lower propagation lengths. At longer propagation lengths, annular beam becomes advantageous. In focused cases, the scintillation index of annular beam is lower than the scintillation index of Gaussian and cos-Gaussian beams starting at earlier propagation distances. Cos-Gaussian beams are advantages at relatively large source sizes while the reverse is valid for annular beams. Scintillations of a stigmatic or astigmatic dark hollow beam can be smaller when compared to stigmatic or astigmatic Gaussian, annular and flat-topped beams under conditions that are closely related to the beam parameters. Intensity fluctuation of an elliptical Gaussian beam can also be smaller than a circular Gaussian beam depending on the propagation length and the ratio of the beam waist size along the long axis to that along the short axis (i.e., astigmatism). Comparing against the fundamental Gaussian beam on equal source size and equal power basis, it is observed that the scintillation index of the lowest order Bessel-Gaussian beam is lower at large source sizes and large width parameters. However, for excessively large width parameters and beyond certain propagation lengths, the advantage of the lowest order Bessel-Gaussian beam seems to be lost. Compared to Gaussian beam, laser array beam exhibits less scintillations at long propagation ranges and at some midrange radial displacement parameters. When compared among themselves, laser array beams tend to have reduced scintillations for larger number of beamlets, longer wavelengths, midrange radial displacement parameters, intermediate Gaussian source sizes, larger inner scales and smaller outer scales of turbulence. The number of beamlets used does not seem to be so effective in this improvement of the scintillations.

PROCEEDINGS ARTICLE | April 22, 2008

Incoherent sinusoidal-Gaussian and annular beam scintillations

Proc. SPIE. 6936, Fourteenth International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics

KEYWORDS: Gaussian beams, Sensors, Receivers, Wave propagation, Turbulence, Scintillation, Atmospheric turbulence, Spherical lenses, Atmospheric scintillation, Atmospheric optics

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The scintillation index is evaluated in horizontal turbulent atmospheric optical links for incidences of incoherent cosh-Gaussian (IChG), cos-Gaussian (ICG) and annular (IA) beams. Weak turbulence solution is obtained for a slow detector. Dependence of the intensity fluctuations of the IChG, ICG and IA beams on the link length, source size, wavelength and the structure constant are examined. At all the link lengths, fixed size IChG and ICG beams exhibit lower scintillations for larger absolute displacement parameters. At a fixed link length, IChG beam yields lower fluctuations than the ICG beam having the same absolute displacement parameter. For the same size primary beams, IA beam with narrower ring scintillates less than the IA beam with wider ring, and this holds to be valid for each link length. Investigation of the scintillation versus the source size reveals that increase in the source size lowers the scintillations for all types of the incoherent beams. At the same source size and the same absolute displacement parameter, IChG beams have lower fluctuations than the ICG beams, larger absolute displacement parameters exhibiting lower scintillations at the same source size for both beams. For IA beams, as the size of the primary beam is increased, the scintillations are reduced for all ring sizes, the reduction being pronounced for narrower rings. As the wavelength increases, the scintillations of IChG and ICG beams first increase, then at around the wavelength forming the Fresnel zone, the scintillations start to decrease and eventually for all types of IChG and ICG beams, the scintillation indices merge towards a certain value. Similar behaviour of the scintillations versus the wavelength is observed for IA beams as well. As long as the structure constant is kept within the range of interest to remain in the weak turbulence, raising the structure constant first increases the intensity fluctuations of beams for all the mentioned beam types where further rises in the structure constant result in the same level of scintillation index. Comparison of the scintillations of IChG, ICG and IA beams with their coherent counterparts and the coherent Gaussian beam shows that the IChG, ICG and IA beams are favorable for large sized sources.

SPIE Journal Paper | September 1, 2007

Angle-of-arrival fluctuations for general-type beams

Eyyuboglu, Halil , Baykal, Yahya

OE Vol. 46 Issue 09

KEYWORDS: Turbulence, Atmospheric optics, Gaussian beams, Receivers, Atmospheric propagation, Optical engineering, Correlation function, Beam propagation method, Atmospheric turbulence, Wave propagation

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PROCEEDINGS ARTICLE | June 13, 2007

Intensity fluctuations of focused general-type beams in atmospheric optics links

Proc. SPIE. 6603, Noise and Fluctuations in Photonics, Quantum Optics, and Communications

KEYWORDS: Gaussian beams, Wave propagation, Collimation, Turbulence, Scintillation, Atmospheric turbulence, Atmospheric propagation, Beam propagation method, Stereolithography, Atmospheric optics

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The intensity fluctuations of focused general-type beams in weakly turbulent atmospheric links are formulated and numerically evaluated. Focused general-type beams in general cover very large range of beams, however in this work we concentrate specifically on the focused sinusoidal-Gaussian, annular and flat-topped beams. The behavior of the scintillations for these beams is examined versus the focusing distance, wavelength of operation and the source size. In our formulation, atmospheric turbulence is introduced through the Rytov method where the free space field (i.e., in the absence of turbulence) at the receiver plane for the general-type focused beam is found by utilizing the Huygens-Fresnel principle. Figures are presented showing the scintillation index for focused general-type beams and collimated general-type beams. To find out the source and medium parameters that will yield favourable scintillation levels, the intensity fluctuations of the focused sinusoidal-Gaussian, annular and flat-topped beams are compared. Within the range of selected source and medium parameters, our observations indicate that the intensity fluctuations in weak turbulence tend to be the smallest for the focused flat-topped Gaussian beams and the largest for the focused cos-Gaussian beams. Gaussian, cosh-Gaussian and annular beams experience interim level fluctuations. The comparison of the scintillation levels for the mentioned types of focused beams follow the same tendency for all the propagation distances. Also, the intensity fluctuations of the focused general-type beams in turbulence are compared with their collimated counterparts. Such a comparison reveals that for all the beams at a selected source size, the scintillations are nearly the same for both the focused and the collimated cases at all the propagation distances, except for the flat-topped Gaussian beams. When focused flat-topped Gaussian beams are employed, the intensity fluctuations seem to be lower as compared to the equivalent collimated flat-topped Gaussian beam at shorter link lengths.

PROCEEDINGS ARTICLE | November 1, 2006

Beams with arbitrary field profiles in turbulence

Proc. SPIE. 6522, Thirteenth Joint International Symposium on Atmospheric and Ocean Optics/ Atmospheric Physics

KEYWORDS: Gaussian beams, Receivers, Telecommunications, Turbulence, Scintillation, Atmospheric turbulence, Spherical lenses, Atmospheric propagation, Beam propagation method, Atmospheric optics

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PROCEEDINGS ARTICLE | September 1, 2006

Intensity fluctuations for source arrays in turbulent atmosphere

Proc. SPIE. 6303, Atmospheric Optical Modeling, Measurement, and Simulation II

KEYWORDS: Silver, Fourier transforms, Optical testing, Scintillation, Chemical elements, Atmospheric modeling, Atmospheric optics, Correlation function

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SPIE Journal Paper | May 1, 2006

Effect of source spatial partial coherence on the angle-of-arrival fluctuations for free-space optics links

Baykal, Yahya , Eyyuboglu, Halil

OE Vol. 45 Issue 05

KEYWORDS: Turbulence, Free space optics, Coherence (optics), Receivers, Optical engineering, Atmospheric optics, Infrared radiation, Atmospheric propagation, Laser sources, Distance measurement

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PROCEEDINGS ARTICLE | April 21, 2006

Propagation of cross beams through atmospheric turbulence

Proc. SPIE. 6160, Twelfth Joint International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics

KEYWORDS: Gaussian beams, Atmospheric propagation engineering, Receivers, Free space, Turbulence, Palladium, Picosecond phenomena, Atmospheric turbulence, Atmospheric propagation, Beam propagation method

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SPIE Journal Paper | April 1, 2006

Higher order annular Gaussian laser beam propagation in free space

Eyyuboglu, Halil , Yenice, Yusuf , Baykal, Yahya

OE Vol. 45 Issue 03

KEYWORDS: Laser beam propagation, Receivers, Beam shaping, Gaussian beams, Free space, Silver, Optical engineering, Free space optics, Atmospheric propagation, Beam propagation method

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SPIE Journal Paper | May 1, 2005

Analysis of laser multimode content on the angle-of-arrival fluctuations in free-space optics access systems

Eyyuboglu, Halil , Baykal, Yahya

OE Vol. 44 Issue 05

KEYWORDS: Free space optics, Receivers, Turbulence, Optical engineering, Atmospheric propagation, Modes of laser operation, Transmission electron microscopy, Spherical lenses, Telecommunications, Atmospheric turbulence

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PROCEEDINGS ARTICLE | December 15, 2004

Cosine-Gaussian laser beam intensity in turbulent atmosphere

Proc. SPIE. 5743, Eleventh International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics

KEYWORDS: Gaussian beams, Receivers, Free space, Wave propagation, Turbulence, Free space optics, Beam shaping, Atmospheric propagation, Beam propagation method, Atmospheric optics

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PROCEEDINGS ARTICLE | December 15, 2004

Rate averaging in free space optics systems using incoherent sources

Proc. SPIE. 5743, Eleventh International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics

KEYWORDS: Modulation, Receivers, Free space, Telecommunications, Turbulence, Free space optics, Scintillation, Atmospheric turbulence, Rubidium, Atmospheric optics

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PROCEEDINGS ARTICLE | May 25, 2004

Effects of laser multimode content on the angle-of-arrival fluctuations in free-space optical access systems

Proc. SPIE. 5473, Noise in Communication

KEYWORDS: Wavefronts, Receivers, Transmission electron microscopy, Telecommunications, Turbulence, Optical resonators, Free space optics, Atmospheric turbulence, Modes of laser operation, Atmospheric propagation

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