Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411

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  • Article
    Citation - WoS: 4
    Citation - Scopus: 6
    Scintillation of Laser Beams in Weak Atmospheric Turbulence for Aerial Vehicle in the Use of Lidar
    (Ieee-inst Electrical Electronics Engineers inc, 2022) Baykal, Yahya; Gercekcioglu, Hamza
    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.
  • Article
    Citation - WoS: 81
    Citation - Scopus: 98
    Underwater Turbulence, Its Effects on Optical Wireless Communication and Imaging: a Review
    (Elsevier Sci Ltd, 2022) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.
    Theory of optical turbulence in underwater medium and the effects of underwater turbulence on various ap-plications done in underwater or under ocean are reviewed. A detailed survey of underwater turbulence studies in literature is reported. Underwater physics covering salinity, temperature and dissipation rates, various power spectra such as Hill, Nikishov and Nikishov, Li, new form and the oceanic turbulence optical power spectrum (OTOPS) spectra are explained. Wave and phase structure functions, related coherence length, anisotropy, in-tensity, field correlations in underwater turbulence are elaborated. Scintillation indices of spherical, plane, Gaussian, and other types of optical beams are mentioned. Bit-error-rate (BER), signal-to-noise-ratio (SNR) performances of optical wireless communication systems operating in underwater, and the effects of modulation types of these systems on the performances are reported. Channel capacity of underwater optical wireless communication systems when the channel experiences log-normal, gamma-gamma, Weibull, and negative exponential statistics are reflected. Underwater imaging and the related modulation transfer function, under-water turbulence mitigation techniques in the form of aperture averaging, adaptive optics, receiver, transmitter and multiple-input, multiple-output (MIMO) spatial diversity techniques are revised.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 8
    Squeezed State Generation Using Cryogenic Inp Hemt Nonlinearity
    (Iop Publishing Ltd, 2023) Salmanogli, Ahmad
    This study focuses on generating and manipulating squeezed states with two external oscillators coupled by an InP HEMT operating at cryogenic temperatures. First, the small-signal nonlinear model of the transistor at high frequency at 5 K is analyzed using quantum theory, and the related Lagrangian is theoretically derived. Subsequently, the total quantum Hamiltonian of the system is derived using Legendre transformation. The Hamiltonian of the system includes linear and nonlinear terms by which the effects on the time evolution of the states are studied. The main result shows that the squeezed state can be generated owing to the transistor's nonlinearity; more importantly, it can be manipulated by some specific terms introduced in the nonlinear Hamiltonian. In fact, the nonlinearity of the transistors induces some effects, such as capacitance, inductance, and second-order transconductance, by which the properties of the external oscillators are changed. These changes may lead to squeezing or manipulating the parameters related to squeezing in the oscillators. In addition, it is theoretically derived that the circuit can generate two-mode squeezing. Finally, second-order correlation (photon counting statistics) is studied, and the results demonstrate that the designed circuit exhibits antibunching, where the quadrature operator shows squeezing behavior.
  • Article
    Citation - WoS: 9
    Citation - Scopus: 13
    Fiber-Coupling Efficiency of Laser Array Beam From Turbulent Atmosphere To Fiber Link
    (Ieee-inst Electrical Electronics Engineers inc, 2023) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin Caner
    Free-space optical communication (FSOC) systems are nowadays integrated with fiber optical components developed for fiber-optic communications. In such integrated systems, the collected portion of the incident beam on the receiver lens is coupled into a single-mode fiber. The process of coupling, however, is mostly affected by the atmospheric turbulence which distorts the coherency of the propagating beam i.e., it results in speckle over the coupling lens causing a reduction in the coupling efficiency. In this article, we aimed at investigating the fiber coupling efficiency of laser array beams propagating in a turbulent atmosphere. For this purpose, using the Huygens-Fresnel principle, mutual coherence function (MCF) for a laser array beam incidence is formulated. In this way, the average power coupled into the fiber and the average received power on the coupling lens are derived for a laser array beam incidence. It is found that the fiber coupling efficiency clearly increases with the increase in ring radius and the number of Gaussian beams in the array and rapidly decreases with increasing structure constant of atmosphere, link distance, and the number of speckles over the receiver aperture. We also demonstrate the effect of various FSOC system parameters on the coupling efficiency.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Dynamical System Parameter Identification Using Deep Recurrent Cell Networks Which Gated Recurrent Unit and When
    (Springer London Ltd, 2021) Akagunduz, Erdem; Cifdaloz, Oguzhan
    In this paper, we investigate the parameter identification problem in dynamical systems through a deep learning approach. Focusing mainly on second-order, linear time-invariant dynamical systems, the topic of damping factor identification is studied. By utilizing a six-layer deep neural network with different recurrent cells, namely GRUs, LSTMs or BiLSTMs; and by feeding input/output sequence pairs captured from a dynamical system simulator, we search for an effective deep recurrent architecture in order to resolve the damping factor identification problem. Our study's results show that, although previously not utilized for this task in the literature, bidirectional gated recurrent cells (BiLSTMs) provide better parameter identification results when compared to unidirectional gated recurrent memory cells such as GRUs and LSTM. Thus, indicating that an input/output sequence pair of finite length, collected from a dynamical system and when observed anachronistically, may carry information in both time directions to predict a dynamical systems parameter.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 17
    Entanglement Sustainability Improvement Using Optoelectronic Converter in Quantum Radar (Interferometric Object-Sensing)
    (Ieee-inst Electrical Electronics Engineers inc, 2021) Salmanogli, Ahmad; Gokcen, Dincer
    In this study, the main focus is laid on the design of an optoelectronic converter as a part of the quantum radar to enhance the entanglement between retained and returned modes at high temperatures. The electro-opto-mechanical converter has been widely studied, and the results showed that the operation at high temperature is so crucial to generate and preserve the entanglement between modes. The main problem arises because the mechanical part operating at a low frequency leads to a large number of thermally excited photons, and eventually, the entanglement between modes becomes lost. To solve the problem, we replace the mechanical part with the optoelectronic components. The optical cavity is coupled to the microwave cavity in the newly designed system through a Varactor diode excited by a photodetector. As the main goal, to improve the entanglement sustainability, the effect of the coupling factor of the microwave cavity to photodetector is investigated. The results show that the mentioned factor creates some degrees of freedom to enhance the entanglement at high temperatures compared to the electro-opto-mechanical converter. At some specific values of the coupling factor, the retained and returned fields remained completely entangled up to 5.5 K and partially entangled around 50 K.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 8
    Design of Quantum Sensor To Duplicate European Robins Navigational System
    (Elsevier Science Sa, 2021) Salmanogli, Ahmad; Gokcen, Dincer
    In this article, we design a quantum device to duplicate the European Robins procedure to precisely deter-mine the migratory route. In the mentioned procedure, the important issue is the geomagnetic field effect on the magnetic momentum of the created radical pairs (triplet-singlet states) dancing with a special fre-quency. To duplicate the procedure, a quantum sensor consisting of two coincident tripartite systems is designed. Each tripartite system is independently excited with the entangled photons (signal and idler). The interesting point is that by manipulation of the system in the right condition, the microwave cavities modes separately affected by the entangled photons can be entangled. The entangled microwave photons play the same role as the triplet-singlet states present in the bird's navigational system. The key point in the design of the quantum sensor is that the entanglement between microwave photons can be strongly affected by the external magnetic field. In fact, this is the criterion employed by the quantum sensor to sense the magnetic field intensity and the direction. To analyze the system, the canonical quantization (or microscopic) method is used to determine the sensor's Hamiltonian, and also the system dynamics equations of motions are analytically derived using Heisenberg-Langevin equations. (c) 2021 Elsevier B.V. All rights reserved.
  • Article
  • Article
    Citation - WoS: 6
    Citation - Scopus: 7
    Optical and Microcavity Modes Entanglement by Means of Plasmonic Opto-Mechanical System
    (Ieee-inst Electrical Electronics Engineers inc, 2020) Salmanogli, Ahmad; Gecim, H. Selcuk
    In this study, plasmonic opto-mechanical tripartite system is proposed to improve the performance of the traditional tripartite opto-mechanical system. In the new design, significantly, optical cavity and microwave cavity modes are directly coupled to each other. The originality of this work consists in embedding a microsphere in the optical cavity where the plasmon-plasmon interaction between the metal plates generates a plasmon mode inside the optical cavity and changes the electric field distribution. The plasmonic property influences the microsphere electrical properties and interacts with the photonic mode inside the optical cavity by which the microwave cavity properties are also affected through coupling to the optical cavity. Microsphere introduces a capacitor as a function of plasmonic properties that can strongly influence the microwave cavity resonance frequency. That is the feature that we want to utilize to enhance the performance of the system at high temperature. The results show that the optical cavity and microwave cavity modes remain entangled at high temperature. It is contributed to the plasmonic-based capacitor induced by the microsphere which is not affected by the thermally induced photons (noise). It is worth mentioning that the induced noise strongly restricts the traditional tripartite system operated with a wide bandwidth.
  • Article
    Entangled Two-Photon Interference
    (Elsevier Gmbh, 2019) Salmanogli, Ahmad
    This article proposes a theoretical solution to one of the original problems of the double-slit experiment, which expresses that it is impossible to identify the photon's path without disturbing it We contend that using the entangled two-photon (signal and idler photons) and inserting a double-slit into the beam of signal (idler) photon, it is possible to distinguish the path of signal (idler) photon, just by the detection of the idler (signal) photon. Basically, the signal and idler photons are highly correlated to each other due to the momentum conservation. Indeed, the photon-photon correlation originates the nonlocal interference effect, so using this effect, lets us know about which path the photon goes through, with its conjugate photon's position detection rather than its detection.