Person: GÜLBAHAR, Burhan Cahit
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Burhan Cahit
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GÜLBAHAR
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ArticlePublication Metadata only Energy harvesting and magneto-inductive communications with molecular magnets on vibrating graphene and biomedical applications in the kilohertz to terahertz band(IEEE, 2017-09) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitMagneto-inductive (MI) Terahertz (THz) wireless channels provide significant theoretical performances for MI communications (MIC) and wireless power transmission (WPT) in nanoscale networks. Energy harvesting (EH) and signal generation are critical for autonomous operation in challenging mediums including biomedical channels. State of the art electromagnetic vibrational devices have millimeter dimensions while targeting low frequency EH without any real-time communications. In this paper, graphene resonators are combined with single molecule magnets (SMMs) to realize nanoscale EH, MIC, and WPT with novel modulation methods achieving simultaneous wireless information and PT. The unique advantages of graphene including atomic thickness, ultra-low weight, high strain, and resonance frequencies in the Kilohertz to THz band are combined with high and stable magnetic moments of Terbium (III) bis (phthalocyanine) SMMs. Numerical analyses provide tens of nanowatts powers and efficiencies of 10 4W/m3 in acoustic and ultrasound frequencies comparable with vibrational EH devices while millimeter wave carrier generation is numerically analyzed. Proposed model and communication theoretical analysis present a practical framework for challenging applications in the near future by promising simple mechanical design. Applications include nanoscale biomedical tagging including human cells, sensing and communication for diagnosis and treatment, EH and modulation for autonomous nano-robotics, and magnetic particle imaging.ArticlePublication Open Access 3D neuromorphic wireless power transfer and energy transmission based synaptic plasticity(IEEE, 2019) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitEnergy consumption combined with scalability and 3D architecture is a fundamental constraint for brain-inspired computing. Neuromorphic architectures including memristive, spintronic, and floating gate metal-oxide-semiconductors achieve energy efficiency while having challenges of 3D design and integration, wiring and energy consumption problems for architectures with massive numbers of neurons and synapses. There are bottlenecks due to the integration of communication, memory, and computation tasks while keeping ultra-low energy consumption. In this paper, wireless power transmission (WPT)-based neuromorphic design and theoretical modeling are proposed to solve bottlenecks and challenges. Neuron functionalities with nonlinear activation functions and spiking, synaptic channels, and plasticity rules are designed with magneto-inductive WPT systems. Tasks of communication, computation, memory, and WPT are combined as an all-in-one solution. Numerical analysis is provided for microscale graphene coils in sub-terahertz frequencies with unique neuron design of coils on 2D circular and 3D Goldberg polyhedron substrates as a proof-of-concept satisfying nonlinear activation mechanisms and synaptic weight adaptation. Layered neuromorphic WPT network is utilized to theoretically model and numerically simulate pattern recognition solutions as a simple application of the proposed system design. Finally, open issues and challenges for realizing WPT-based neuromorphic system design are presented including experimental implementations.ArticlePublication Metadata only Theoretical analysis of magneto-inductive THZ wireless communications and power transfer with multi-layer graphene nano-coils(IEEE, 2017-03) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitGraphene with significant potentials in diverse areas of physical and biological sciences is proposed as a solution to complementary problems of semiconductor and biomedical industries, i.e., the on-chip (OC) interconnect bottleneck and in-body (IB) wireless communications/power transfer (PT), respectively. Emerging nanoscale solutions with radio frequency, optical, ultrasonic, or molecular channels in OC and IB media have various challenges including achievable footprints and frequency, energy consumption, medium dependent features, and interference. In this paper, major challenges are addressed with magneto-inductive (MI) transceivers by combining the advantages of THz operation frequency, unique features of intercalated multi-layer graphene (MLG) coils and range extension with MI waveguides. Our design promises scalable and high performance solutions for the OC interconnect bottleneck while providing biocompatible and universal solutions for challenging IB medium. The proposed solution is theoretically analyzed and numerically compared with the copper-based alternatives, and the practical challenges are discussed. Simulation results achieve high capacity (several Tbit/s) and ultra-low power (500 zJ/bit) wireless communications while providing high (hundreds of kWs) and efficient (109 W/mm2) wireless PT at several millimeters. In addition, unique properties of MLG such as lightweight structure, biocompatibility, current carrying capacity, and planar manufacturability make the solution more promising for challenging environments.ArticlePublication Open Access Theory of quantum path computing with Fourier optics and future applications for quantum supremacy, neural networks and nonlinear Schrödinger equations(Nature Research, 2020-07-03) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitThe scalability, error correction and practical problem solving are important challenges for quantum computing (QC) as more emphasized by quantum supremacy (QS) experiments. Quantum path computing (QPC), recently introduced for linear optic based QCs as an unconventional design, targets to obtain scalability and practical problem solving. It samples the intensity from the interference of exponentially increasing number of propagation paths obtained in multi-plane diffraction (MPD) of classical particle sources. QPC exploits MPD based quantum temporal correlations of the paths and freely entangled projections at different time instants, for the first time, with the classical light source and intensity measurement while not requiring photon interactions or single photon sources and receivers. In this article, photonic QPC is defined, theoretically modeled and numerically analyzed for arbitrary Fourier optical or quadratic phase set-ups while utilizing both Gaussian and Hermite-Gaussian source laser modes. Problem solving capabilities already including partial sum of Riemann theta functions are extended. Important future applications, implementation challenges and open issues such as universal computation and quantum circuit implementations determining the scope of QC capabilities are discussed. The applications include QS experiments reaching more than 2(100) Feynman paths, quantum neuron implementations and solutions of nonlinear Schrodinger equation.ArticlePublication Open Access Theory of quantum path entanglement and interference with multiplane diffraction of classical light sources(MDPI, 2020-02-21) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitQuantum history states were recently formulated by extending the consistent histories approach of Griffiths to the entangled superposition of evolution paths and were then experimented with Greenberger-Horne-Zeilinger states. Tensor product structure of history-dependent correlations was also recently exploited as a quantum computing resource in simple linear optical setups performing multiplane diffraction (MPD) of fermionic and bosonic particles with remarkable promises. This significantly motivates the definition of quantum histories of MPD as entanglement resources with the inherent capability of generating an exponentially increasing number of Feynman paths through diffraction planes in a scalable manner and experimental low complexity combining the utilization of coherent light sources and photon-counting detection. In this article, quantum temporal correlation and interference among MPD paths are denoted with quantum path entanglement (QPE) and interference (QPI), respectively, as novel quantum resources. Operator theory modeling of QPE and counterintuitive properties of QPI are presented by combining history-based formulations with Feynman's path integral approach. Leggett-Garg inequality as temporal analog of Bell's inequality is violated for MPD with all signaling constraints in the ambiguous form recently formulated by Emary. The proposed theory for MPD-based histories is highly promising for exploiting QPE and QPI as important resources for quantum computation and communications in future architectures.ArticlePublication Metadata only Stochastic resonance in graphene bilayer optical nanoreceivers(IEEE, 2014-11) Kocaoglu, M.; Gülbahar, Burhan; Akan, O. B.; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitGraphene, a 2-D sheet of carbon atoms, is believed to have diverse application areas ranging from medicine to communications. A novel application is using graphene as a photodetector in optical communications due to its superior optical and electrical properties such as wide and tunable absorption frequency range and high electron mobility. Noise, which is especially significant in nanoscale communications, is mostly seen as an adversary. Stochastic resonance (SR) is the performance enhancement of a system due to incorporation of noise. It is shown that the excess noise in nanocommunications can be used to improve the performance of a graphene bilayer photodetector system with hard threshold decoder, when received signals are subthreshold. SR arises due to the nonlinear nature of the hard decoder. First, the SR effect due to the background ambient noise and intentional light noise is analyzed. An approximate inverse signal-to-noise ratio expression is derived, which maximizes the mutual information. The effect of frequency on the mutual information is also investigated, and it is shown that the higher frequencies are more preferable for noise limited regimes. Later, the case with the intentional noise added to the top gate is investigated. It is shown that significant mutual information improvements are achieved for subthreshold signals, due to the multiplicative stochastic terms arising from the nonlinear graphene bilayer characteristics, i.e., the exponential dependence of photocurrent on the gate voltages. All the analytical results are verified with extensive simulations.ArticlePublication Metadata only A communication theoretical analysis of multiple-access channel capacity in magneto-inductive wireless networks(IEEE, 2017-06) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitMagneto-inductive (MI) wireless communications is an emerging subject with a rich set of applications, including local area networks for the Internet-of-Things, wireless body area networks, in-body and on-chip communications, and underwater and underground sensor networks as a low-cost alternative to radio frequency, acoustic or optical methods. Practical MI networks include multiple access channel (MAC) mechanisms for connecting a random number of coils without any specific topology or coil orientation assumptions covering both short and long ranges. However, there is not any information theoretical modeling of MI MAC (MIMAC) capacity of such universal networks with fully coupled frequency selective channel models and exact 3-D coupling model of circular coils instead of long range dipole approximations. In this paper, K-user MIMAC capacity is information theoretically modeled and analyzed, and two-user MIMACs are modeled with explicitly detailed channel responses, bandwidths and coupled thermal noise. K-user MIMAC capacity is achieved through Lagrangian solution with K-user water-filling optimization. Optimum orientations maximizing capacity and received power are theoretically analyzed, and numerically simulated for two-user MIMACs. Constructive gain and destructive interference mechanisms on MIMACs are introduced in comparison with the classical interference based approaches. The theoretical basis promises the utilization of MIMACs in 5G architectures.ArticlePublication Metadata only Quantum spatial modulation of optical channels: Quantum boosting in spectral efficiency(IEEE, 2019-11) Gülbahar, Burhan; Memisoglu, G.; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitSpatial modulation (SM) improves spectral efficiency (SE) by creating the constellation of active optical antenna indices. However, quantum properties of light are not exploited to improve the SE. In this letter, multi-plane diffraction (MPD) set-up creating exponentially increasing number of propagation paths for classical sources is exploited to introduce quantum spatial modulation (QSM). Exponential number of paths and quantum superposition-based classical symbol generation for transmitting simultaneous multiple classical symbols are exploited for linear and exponential quantum boosting of SM, respectively. It is theoretically modeled, numerically analyzed, and the challenges of joint design of source-channel coding and QSM are discussed.ArticlePublication Open Access Space-track modulation and coding for high density aerial vehicle downlink networks with free space optical and visible light communications(TÜBİTAK, 2019) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitAerial vehicles (AVs) have challenges in terms of realizing low complexity and wide coverage area wireless communications architectures, especially for crowded or high density groups of AVs with state-of-the-art free space optical (FSO) and radio frequency (RF) based system designs. FSO architectures generally target point-to-point high gain directional links while requiring strict acquisition and tracking due to the narrow beam width of laser transmitters with challenges of vibration, turbulence, misalignment, atmospheric absorption, scattering, and fading. In this article, a novel multiuser free space optical system design of modulation and coding denoted by space-track modulation and coding (STMC) is proposed for crowded downlink communications. STMC does not require high accuracy tracking and costly system components by utilizing large beam divergence angles, more transmitter units with smaller aperture sizes and weights, and large spatial regions to receive modulated data at AV tracks. In addition, the spatio-optical wireless caching problem is introduced for AV networks while defining STMC problem information theoretically. STMC combines track based multiuser modulation and coding, with geographical and positional data for low data rate broadcasting applications with wide area coverage. Numerical simulations provide tens of bit/s data rates for thousands of kilometers of coverage area while simultaneously serving a significantly larger number of AVs. Finally, future works and open issues are discussed. The novel modulation and coding mechanisms are promising future applications for both high altitude AVs and low altitude drone networks with low complexity hardware for multiuser low data rate communications.ArticlePublication Metadata only CSSTag: optical nanoscale radar and particle tracking for in-body and microfluidic systems with vibrating graphene and resonance energy transfer(IEEE, 2017-12) Gülbahar, Burhan; Memisoglu, G.; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitBiological particle tracking systems monitor cellular processes or particle behaviors with the great accuracy. The emissions of fluorescent molecules or direct images of particles are captured with cameras or photodetectors. The current imaging systems have challenges in detection, collection, and analysis of imaging data, penetration depth, and complicated set-ups. In this paper, a signaling-based nanoscale acousto-optic radar and microfluidic multiple particle tracking (MPT) system is proposed based on the theoretical design providing nanoscale optical modulator with vibrating Förster resonance energy transfer and vibrating cadmium selenide/zinc sulfide quantum dots (QDs) on graphene resonators. The modulator combines significant advantages of graphene membranes having wideband resonance frequencies with QDs having broad absorption spectrum and tunable properties. The solution denoted by chirp spread spectrum (CSS) Tag utilizes classical radar target tracking approaches in nanoscale environments based on the capabilityto generate CSS sequences identifying different bio-particles. Monte Carlo simulations show significant performance for MPT with a modulator of 10 μm × 10 μm × 10 μm dimension and several picograms of weight, the signal-to-noise ratio in the range from -7 to 10 dB, simple light emitting diode sources with power less than 4 W/cm2 and high speed tracking for microfluidic environments.