Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651

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Now showing 1 - 10 of 65
  • Article
    Laser Ablation Device with a Closed-Loop Control System
    (Optica Publishing Group, 2025) Beldek, Ulas; Erdogan, Kubra; Arpali, Caglar; Baykal, Yahya
    A laser ablation device with real-time beam power control is designed and implemented. This platform regulates the intensity of the laser beam by continuously measuring its intensity distribution. The quality of the ablation process is optimized through a closed-loop control system that uses a rule-based decision-making approach. The controller generates a starting signal for both the laser power and the motors based on the estimated quality of the ablation. The effects of laser power and light intensity on the formation of microchannels in polymethylmethacrylate material were investigated using the laser beam. The quality of the ablation geometry was assessed through image processing and inspection under a scanning electron microscope. The generated microchannels were analyzed in terms of roughness and residual thermal stress. A comparison of the experimental results with theoretical calculations and simulations revealed that the closed-loop control of laser beam power is effective for material etching and for creating smoother channel profiles. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
  • Article
    Effects of Receiver Diversity on Bit Error Rate of Underwater Optical Wireless Communication Systems in Weak Oceanic Turbulence
    (Springer, 2025) Gokce, Muhsin Caner; Baykal, Yahya; Ata, Yalcin
    The receiver spatial diversity techniques are employed in underwater optical wireless communication (OWC) systems to mitigate oceanic turbulence, improving the bit error rate performance. In this paper, we consider an OWC system employing a binary phase-shift keying (BPSK) modulated Gaussian beam at the transmitter and employing receiver spatial diversity at the receiver. The techniques for receiver spatial diversity systems considered in the study are selection combining (SC), equal gain combining (EGC), and the maximum ratio combining (MRC). The bit error rate (BER) performance of the OWC system operating in weak oceanic turbulence is investigated by calculating the Gaussian beam's turbulence-induced scintillation index and the received optical intensity. It is found that the receiver spatial diversity techniques, especially EGC and MRC, are very effective for reducing the BER of an OWC system in weak oceanic turbulence. Furthermore, the BER performance of the underwater OWC system sees an improvement with an increase in the number of photodetectors or a decrease in the level of oceanic turbulence. Moreover, an improvement in the photodetector responsivity or a reduction in the system's noise factor contributes to achieving a favorable BER performance.
  • Article
    Citation - Scopus: 1
    Multimode Laser Beam Field Correlations for Vertical Links Operating in Oceanic Turbulence
    (IEEE-Inst Electrical Electronics Engineers inc, 2025) Gercekcioglu, Hamza; Baykal, Yahya; Gokce, Muhsin Caner; Caner Gokce, Muhsin
    In underwater optical vertical link medium, based on the extended Huygens-Fresnel principle, multimode laser beam field correlation is derived and evaluated analytically in the Atlantic Ocean at high latitude and high latitude- low latitudes. With the depth of seawater, the coherence length of a spherical wave operating in the underwater turbulent medium is demonstrated for the range of 0-4000 m. By utilizing the coherence length varying with parameters such as the rate of dissipation of turbulent kinetic energy per unit mass of fluid epsilon, the rate of dissipation of the mean squared temperature chi(T) and non-dimensional representing the relative strength of temperature and salinity fluctuations omega, which depend on depth, the field correlation is examined in detail for single modes and multimode. Their variations are exhibited. Our results indicate clearly that as the mode increases, field correlation gets better.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Scintillations of Higher-Order Optical Beams in Biological Tissues
    (Optica Publishing Group, 2025) Baykal, Yahya; Gokce, Muhsin Caner; Ata, Yalcin; Gercekcioglu, Hamza
    The Scintillation index of a higher-order laser beam in turbulent biological tissue is formulated and evaluated. Behaviors of the scintillation indices of various higher-order beams against the tissue turbulence parameters of the strength coefficient of the refractive index fluctuations, fractal dimension, characteristic length of heterogeneity, small length-scale factor, and the source size, tissue length, and wavelength are examined. Fluctuations in the intensity are also investigated when various types of tissues, such as the intestinal epithelium (mouse), liver parenchyma (mouse), and upper dermis (human), are excited by different higher-order laser beams. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Structure Functions for Optical Waves in a Complex Medium of Turbulent Biological Tissues
    (Optica Publishing Group, 2022) Ata, Yalcin; Baykal, Yahya; Gokce, Muhsin caner
    Although optical wave propagation is investigated based on the absorption and scattering in biological tissues, the turbulence effect can also not be overlooked. Here, the closed-form expressions of the wave structure func-tion (WSF) and phase structure function (PSF) of plane and spherical waves propagating in biological tissue are obtained to help with future research on imaging, intensity, and coherency in turbulent biological tissues. This paper presents the effect of turbulent biological tissue on optical wave propagation to give a perception of the per-formance of biomedical systems that use optical technologies. The behavior of optical waves in different types of turbulent biological tissues such as a liver parenchyma (mouse), an intestinal epithelium (mouse), a deep dermis (mouse), and an upper dermis (human) are investigated and compared. It is observed that turbulence becomes more effective with an increase in the characteristic length of heterogeneity, propagation distance, and the strength of the refractive index fluctuations. However, an increase in the fractal dimension, wavelength, and small length scale factor has a smaller turbulence effect on the propagating optical wave. We envision that our results may be used to interpret the performance of optical medical systems operating in turbulent biological tissues.(c) 2022 Optica Publishing Group
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Field Correlations of Multimode Optical Beams in Underwater Turbulence
    (Optica Publishing Group, 2024) Baykal, Yahya; Gokce, Muhsin C.; Ata, Yalcin; Gercekcioglu, Hamza
    For multimode optical beams, field correlations at the receiver plane are found in underwater turbulence. Field correlations of single high order beams in underwater turbulence are special cases of our formulation. Variations of field correlations against the underwater turbulence parameters and the diagonal length from various receiver points are examined for different multimode and single high order beams. Stronger underwater turbulence is found to reduce the field correlations of multimode and single high order optical beams. The results will be of help in heterodyne detection analysis and fiber coupling efficiency in an underwater medium experiencing turbulence. (c) 2024 Optica Publishing Group
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Intensity and Degree of Coherence of Vortex Beams in Atmospheric Turbulence
    (Ieee-inst Electrical Electronics Engineers inc, 2024) Gokce, Muhsin Caner; Baykal, Yahya; Gercekcioglu, Hamza; Ata, Yalcin; Caner Gokce, Muhsin
    We utilize the Huygens-Fresnel principle to derive the mutual coherence function (MCF) for a vortex beam, which is the main focus of our investigation. Then, we examine the intensity and modulus of the complex degree of coherence (DOC) characteristics of vortex beams in atmospheric turbulence. Our results indicate that as the topological charge increases, the intensity distribution of the vortex beam becomes less affected by atmospheric turbulence. However, the modulus of the complex DOC decreases.
  • Editorial
    Citation - WoS: 4
    Citation - Scopus: 1
    Intensity Fluctuations of Flat-Topped Beam in Non-Kolmogorov Weak Turbulence: Reply
    (Optical Soc Amer, 2012) Gercekcioglu, Hamza; Baykal, Yahya
    In our recent publication, we have examined the intensity fluctuations of flat-topped beam in non-Kolmogorov weak turbulence [J. Opt. Soc. Am. A 29, 169 (2012)] in which our comparison of the scintillation indices in the Kolmogorov and in various non-Kolmogorov turbulences was based on the same structure constant, no matter what power law the non-Kolmogorov spectrum takes. In such choice of the fixed structure constant, which is also being used by many researchers in the field [Opt. Express 18, 451 (2010); Proc. SPIE 6747, 67470B (2007); Opt. Commun. 285, 880 (2012)], we have found that the variation of the scintillation index against non-Kolmogorov power law exhibits a peak at the worst power law, which happens to be smaller than the Kolmogorov power law of 11/3. Charnotskii commented [J. Opt. Soc. Am. A. 29, 1838 (2012)] on our paper. In this paper, in our to reply to Charnotskii's comment, we have re-evaluated the scintillation index of flat-topped beam in non-Kolmogorov weak turbulence by employing our recently reported equivalent structure constant [Opt. Lett. 36, 4554 (2011)] and re-compared the intensity fluctuations in Kolmogorov and in non-Kolmogorov turbulences. As the result of such re-comparison, the worst power law is observed to disappear. c 2012 Optical Society of America
  • Article
    Citation - WoS: 3
    Citation - Scopus: 2
    Correlations of Multimode Optical Incidences in a Turbulent Biological Tissue
    (Optica Publishing Group, 2023) Gokce, Muhsin Caner; Gerekcioglu, Hamza; Ata, Yalin; Baykal, Yahya; Gerçekcioğlu, Hamza
    In a turbulent biological tissue, field correlations at the observation plane are found when a multimode optical incidence is used. For different multimode structures, variations of the multimode field correlations are evaluated against the biological tissue turbulence parameters, i.e., the strength coefficient of the refractive-index fluctuations, fractal dimension, characteristic length of heterogeneity, and the small length-scale factor. Using a chosen multimode content, for specific biological tissue types of liver parenchyma (mouse), intestinal epithelium (mouse), upper dermis (human), and deep dermis (mouse), field correlations are evaluated versus the strength coefficient of the refractive-index fluctuations and small length-scale factor. Again, with a chosen multimode content, behavior of the field correlations is studied against the strength coefficient of the refractive-index fluctuations for various diagonal lengths and the transverse coordinate at the observation plane. Finally, the field correlation versus the strength coefficient of the refractive-index fluctuations is reported for different single modes, which are special cases of multimode excitation. This topic is being reported in the literature for the first time, to our knowledge, and the presented results can be employed in many important biological tissue applications. (c) 2023 Optica Publishing
  • Article
    Citation - WoS: 1
    Citation - Scopus: 3
    Performance of a Free-Space Optical Communication System Employing Receive Diversity Techniques in Anisotropic Atmospheric Non-Kolmogorov Turbulence
    (Optica Publishing Group, 2022) Gokce, Muhsin Caner; Ata, Yalcin; Baykal, Yahya
    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 toMRC in terms of BER performance. (C) 2022 Optica Publishing Group