Browsing by Author "Baykal, Yahya Kemal"

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Citation Count: Çil, Celal Zaim...et al (2010). "Beam wander of J (0)- and I (0)-Bessel Gaussian beams propagating in turbulent atmosphere", Applied Physics B-Lasers and Optics, Vol. 98, No. 1, pp. 195-202.
Beam wander of J (0)- and I (0)-Bessel Gaussian beams propagating in turbulent atmosphere
(2010) Çil, Celal Zaim; Eyyüboğlu, Halil Tanyer; Baykal, Yahya Kemal; Korotkova, O.; Cai, Y.; 7812
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 Count: Ata, Yalçın; Baykal, Yahya Kemal; Gökçe, Muhsin Caner (2022). "BER performance ofM-ary pulse position modulated communication systems in anisotropic non-Kolmogorov turbulent atmosphere", Waves in Random and Complex Media, Vol. 32, No. 2, pp. 936-946.
BER performance ofM-ary pulse position modulated communication systems in anisotropic non-Kolmogorov turbulent atmosphere
(2022) Ata, Yalçın; Baykal, Yahya Kemal; Gökçe, Muhsin Caner; 7812
We investigated the effect of anisotropic non-Kolmogorov atmospheric turbulence on the performance of the optical wireless systems whenM-ary Pulse Position Modulation (PPM) is applied to a Gaussian beam. The performance of the optical wireless systems that use avalanche photodetector at the receiver is evaluated in terms of the bit error rate (BER). The effects of the parameters, such as the anisotropy factors inx-ydirections, modulation order, data bit rate, equivalent load resistor, photodetector quantum efficiency, non-Kolmogorov turbulence power law exponent, beam source size, link length, photodetector gain and structure constant on BER of theM-ary PPM Gaussian beam propagating in anisotropic non-Kolmogorov atmospheric turbulence, are examined.
Citation Count: Baykal, Yahya. "Editorial: Optical wave propagation and communication in turbulent media", Frontiers in Physics, Vol.11, (2023).
Editorial: Optical wave propagation and communication in turbulent media
(2023) Baykal, Yahya Kemal; 7812
Citation Count: Baykal, Yahya Kemal (2010). "Effects of type of incidence on the second and fourth order moment parameters evaluated in turbulent atmosphere", Optics InfoBase Conference Papers, Frontiers in Optics, FiO 2010.ko
Effects of type of incidence on the second and fourth order moment parameters evaluated in turbulent atmosphere
(2010) Baykal, Yahya Kemal; 7812
Using a general type incidence, the second and fourth order moments are formulated in atmospheric turbulence. Received field and intensity correlations are evaluated and the behaviour of these correlations are compared for different beam types. © 2010 OSA/FiO/LS.
Citation Count: Keskin, Ayşan; Baykal, Yahya Kemal (2021). "Effects of underwater turbulence on average transmittance of cos-Gaussian and cosh-Gaussian optical beams", Waves in Random and Complex Media, Vol. 31, No. 6, pp. 2385-2396.
Effects of underwater turbulence on average transmittance of cos-Gaussian and cosh-Gaussian optical beams
(2021) Keskin, Ayşan; Baykal, Yahya Kemal; 7812
The impacts of underwater turbulence on the average optical transmittance are investigated when optical cosine-Gaussian and optical cosine-hyperbolic-Gaussian (cosh-Gaussian) beam propagate in weakly turbulent underwater medium. Findings obtained by using MATLAB reveal that when the displacement parameter is smaller (larger) for the cos-Gaussian (cosh-Gaussian) beam, the average transmittance increases. Also, an increase in the source size results in elevated average transmittance values. Rate of dissipation of kinetic energy per unit mass of fluid is found to be directly proportional to the average transmittance. However, the rate of dissipation of the mean-squared temperature is inversely proportional to the average transmittance. Average transmittance is found to be essentially the same when the temperature-induced optical turbulence is dominant. An increase in the salinity-induced optical turbulence suddenly reduces the average transmittance of the cos-Gaussian and cosh-Gaussian beam in underwater turbulence. Finally, it is observed that for the same sized beams in the same underwaterturbulent medium, cosh-Gaussian beam will have larger average transmittance than the corresponding cos-Gaussian beam. As the influence and value of our research conclusion on the development of our research, we comment that cosh-Gaussian beams can be preferred over the cos-Gaussian and Gaussian beams in obtaining larger average transmittance in underwater turbulence.
Citation Count: Yalçın, Ata; Baykal, Yahya Kemal (2019). "Field correlation of flat-topped beams in anisotropic non-Kolmogorov turbulent atmosphere", Journal of Modern Optics, Vol. 66, No. 2, pp. 130-135.
Field correlation of flat-topped beams in anisotropic non-Kolmogorov turbulent atmosphere
(2019) Yalçın, Ata; Baykal, Yahya Kemal; 7812
Field correlation of flat-topped beams in anisotropic non-Kolmogorov turbulent atmosphere is formulated and evaluated. Larger anisotropic factor causes higher field correlations. Smaller field correlations are seen when the transverse distance at the receiver plane increases. Smaller field correlations are observed at large off-axis transverse receiver points, which are valid for any anisotropic factor and for any power-law exponent of non-Kolmogorov turbulence. When the flat-topped beam is composed of large number of Gaussian beams, the field correlation becomes smaller. In anisotropic non-Kolmogorov turbulence, longer propagation distances, larger structure constants, smaller inner scales and smaller source sizes decrease the field correlation. Larger power law exponent of non-Kolmogorov turbulence increases the field correlations at any anisotropic factor.
Citation Count: Yalçın, A.; Gökçe, M.C.; Baykal, Yahya Kemal. (2022). "Intensity fluctuations in biological tissues at any turbulence strength", Physica Scripta, Vol.97, No.9.
Intensity fluctuations in biological tissues at any turbulence strength
(2022) Ata, Yalçın; Gökçe, Muhsin Caner; Baykal, Yahya Kemal; 7812
This study investigates the intensity fluctuations of the optical plane and spherical waves in biological tissue that experience any strength of turbulence. Biological tissue is a random and complex medium for optical wave propagation, having a power spectrum reflecting the turbulent characteristics that depend on the structural parameters. It is important to accurately determine the strength of turbulence and classify turbulence regimes for the correct modeling of the behavior of the optical wave propagation. To classify weak, moderate and strong turbulent regimes, closed-form expressions of modified Rytov variances are obtained. Based on the modified Rytov variance that involves the large-scale and small-scale variations, the intensity fluctuations specified by the metric of scintillation index, are calculated versus various parameters such as the propagation distance, refractive index, characteristic length of heterogeneity, small length-scale factor, wavelength, fractal dimension and strength of the refractive index fluctuations. Behavior of optical plane and spherical waves in different turbulent regimes and the comparison of intensity fluctuations in different specimens of human and animal tissues are shown.
Citation Count: Bük, Murat...et al. "Işık hüzmesi profili ölçme sistemi", Çankaya Üniversitesi, 4. Mühendislik ve Teknoloji Sempozyumu, 2011.
Işık hüzmesi profili ölçme sistemi
(2011) Bük, Murat; Baki, T.; Çil, Celal Zaim; Cambaz, Göknur; Baykal, Yahya Kemal; Erseven, S.; Karabulut, S.; Ertuğ, A. Mithat; 7812
Citation Count: Baykal, Yahya Kemal; Yalçın, ata; Gökçe, Muhsin Caner. (2022). "Laser array field correlations in underwater turbulence", Journal of Modern Optics, Vol.69, No.21, pp.1224-1228.
Laser array field correlations in underwater turbulence
(2022) Baykal, Yahya Kemal; Ata, Yalçın; Gökçe, Muhsin Caner; 7812
In underwater turbulent medium, field correlations are found when the incidence is a laser beam array. Variations of the field correlations against the variations in the ring radius of laser array beam, number of beamlets composing the laser array, source size, underwater turbulence parameters, i.e. the ratio of temperature to salinity contributions to the refractive index spectrum, rate of dissipation of mean-squared temperature and rate of dissipation of kinetic energy per unit mass of fluid, are investigated. Field correlations of laser arrays are found to be larger than the field correlations of the single beams. The effect of underwater turbulence is to reduce the field correlation of laser arrays.
Citation Count: Gökçe, Muhsin Caner; Yalçın, Ata; Baykal, Yahya Kemal. (2022). "Performance evaluation of aeronautical uplink/downlink free-space optical communication system with adaptive optics over gamma-gamma turbulence channel", Journal of Optics (United Kingdom), Vol.24, No.10.
Performance evaluation of aeronautical uplink/downlink free-space optical communication system with adaptive optics over gamma-gamma turbulence channel
(2022) Gökçe, Muhsin Caner; Ata, Yalçın; Baykal, Yahya Kemal; 7812
In this study, we analyze the effect of adaptive optics corrections on the performance of an aeronautical free-space optical (FSO) system with bidirectional slant path uplink and downlink communication channels. The aeronautical FSO communication (FSOC) system operates in a gamma-gamma atmospheric turbulence channel and employs adaptive optics corrections for the distorted wave front of the Gaussian beam wave. The modulation type of the aeronautical FSOC system is chosen to be M-ary phase-shift-keying-subcarrier intensity modulation and the type of the employed photodetector is positive-intrinsic-negative. In analysis, the effect of system parameters such as zenith angle, the height of transmitter/receiver on the ground, M-ary level, filter bandwidth, link distance, and the adaptive optics correction modes on bit-error-rate are demonstrated.
Citation Count: Ata, Yalçın; Baykal, Yahya Kemal; Gökçe, Mushin Caner. (2022). "Performance of a free-space optical communication system employing receive diversity techniques in anisotropic atmospheric non-Kolmogorov turbulence", Journal of the Optical Society of America B: Optical Physics, Vol.39, No.8, pp.2100-2108.
Performance of a free-space optical communication system employing receive diversity techniques in anisotropic atmospheric non-Kolmogorov turbulence
(2022) Ata, Yalçın; Baykal, Yahya Kemal; Gökçe, Muhsin Caner; 7812
In this paper, bit error rate (BER) performance of a free-space optical communication (FSOC) system operating in anisotropic non-Kolmogorov weak turbulence is investigated together with the spatial diversity techniques. The spatial diversity techniques are implemented as maximum ratio combining (MRC), equal gain combining (EGC), and selection combining (SC) and applied to the receiver. The propagating beam is the Gaussian beam wave, and the modulation scheme is binary phase-shift keying (BPSK). Results are obtained for various parameters such as the anisotropy factor, non-Kolmogorov power law exponent, photodetector responsivity, equivalent load resistor, electronic bandwidth, Gaussian beam radius, wavelength, propagation distance, and turbulence structure constant. It is found that the spatial diversity technique used at the receiver causes significant improvement in the performance of an FSOC system under the conditions of anisotropic non-Kolmogorov atmospheric turbulence. It is also observed that BER performance improves as the atmospheric turbulence becomes more anisotropic. Among the spatial diversity techniques, SC is inferior to EGC and EGC is inferior to MRC in terms of BER performance.
Citation Count: Gerçekçiıoğlu, Hamza; Baykal, Yahka Kemal. (2022). "Scintillation of Laser Beams in Weak Atmospheric Turbulence for Aerial Vehicle in the Use of LIDAR", IEEE Journal of Selected Topics in Quantum Electronics, Vol.28, No.5.
Scintillation of Laser Beams in Weak Atmospheric Turbulence for Aerial Vehicle in the Use of LIDAR
(2022) Gercekcioglu, Hamza; Baykal, Yahya Kemal; 7812
Formulation of on-axis scintillation of laser beams is found in weak atmospheric turbulence for aerial vehicle in the use of light detection and ranging (LIDAR) systems by employing the Rytov method. The formulation derived for collimated Gaussian, plane and spherical beams is evaluated in vertical link involving up/down link. In this medium, the behavior of these beams in terms of deterioration is examined. In this context, the on-axis scintillation index values are plotted versus normalized target size parameter, target size, source size, propagation distance and zenith angle, and the results are obtained for LIDAR systems operating for aerial vehicle in vertical atmospheric link by using ground/space transceiver. The degradation is greater in operating with ground transceiver than in operating with space transceiver. Additionally, while the on-axis scintillation index is minimized in the smaller target size in use of ground transceiver than in use of space transceiver, that is, it can also be minimized in the larger target size in use of space transceiver. The values of source size and the normalized target size parameter minimizing the obtained scintillation index, are 1.2 cm, 10, and 6 cm and 5 for ground transceiver and space transceiver, respectively.