Researcher:
Tetikol, Hüseyin Serhat

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PhD Student

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Hüseyin Serhat

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Tetikol

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Tetikol, Hüseyin Serhat

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2011 - 20203

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Researcher Of Publications: search.filters.isAuthorOfPublication.364f43e8-1ed2-4e35-a609-e3877d6abe3c

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    Enhancement of resolution and propagation length by sources with temporal decay in plasmonic devices
    (Springer, 2020) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Tetikol, Hüseyin Serhat; Aksun, M. İrşadi; PhD Student; Faculty Member; College of Engineering; College of Engineering; N/A; 28358
    Highly lossy nature of metals has severely limited the scope of practical applications of plasmonics. The conventional approach to circumvent this limitation has been to search for new materials with more favorable dielectric properties (e.g., reduced loss), or to incorporate gain media to overcome the inherent loss. In this study, however, we turn our attention to the source and show that the wealth of new SPP modes with simultaneous complex frequencies and complex wave vectors that are otherwise unreachable can be excited by imposing temporal decay on the excitation. Therefore, to understand the possible implications of these new modes and how to be able to tune them for specific applications, we propose a framework of pseudo-monochromatic modes that are generated by introducing exponential decays into otherwise monochromatic sources. Within this framework, the dispersion relation of complex SPPs is re-evaluated and cast to be a surface rather than a curve, depicting all possible omega-kpairs (both complex in general) that are supported by the given geometry. To demonstrate the potentials of the complex modes and the use of the framework to study them selectively, we have chosen two important, and somewhat limiting, features of SPPs to investigate; resolution in plasmonic lenses and propagation length in SPP waveguides. While the former is mainly used to validate the proposed method and the framework on the recent improvement of resolution in plasmonic superlenses, the latter provides a novel approach to extend the propagation length of the SPP modes in planar waveguides significantly. Since the improvement in propagation length due to the introduction of temporal decay to the excitation is rather counter-intuitive, the dispersion-based theoretical predictions (the proposed approach) have been validated via the FDTD simulations of Maxwell's equations in the same geometry without any a priori assumptions on the frequency or the wave vector.
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    RSSI-fingerprinting-based mobile phone localization with route constraints
    (IEEE Computer Society, 2014) Sevlian, Raffi; Rajagopal, Ram; Varaiya, Pravin; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Tetikol, Hüseyin Serhat; Kontik, Mehmet; Faculty Member; N/A; N/A; College of Engineering; 7211; N/A; N/A
    Accurate positioning of a moving vehicle along a route enables various applications, such as travel-time estimation, in transportation. Global Positioning System (GPS)-based localization algorithms suffer from low availability and high energy consumption. A received signal strength indicator (RSSI) measured in the course of the normal operation of Global System for Mobile Communications (GSM)-based mobile phones, on the other hand, consumes minimal energy in addition to the standard cell-phone operation with high availability but very low accuracy. In this paper, we incorporate the fact that the motion of vehicles satisfies route constraints to improve the accuracy of the RSSI-based localization by using a hidden Markov model (HMM), where the states are segments on the road, and the observation at each state is the RSSI vector containing the detected power levels of the pilot signals sent by the associated and neighboring cellular base stations. In contrast to prior HMM-based models, we train the HMM based on the statistics of the average driver's behavior on the road and the probabilistic distribution of the RSSI vectors observed in each road segment. We demonstrate that this training considerably improves the accuracy of the localization and provides localization performance robust over different road segment lengths by using extensive cellular data collected in Istanbul, Turkey; Berkeley, CA, USA; and New Delhi, India.
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    Optical position feedback and phase control of resonant 1D and 2D MOEMS-scanners
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2011) Tortschanoff, A.; Frank A.; Wildenhain, M.; Sandner, T.; Schenk H.; Kenda, A.; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Tetikol, Hüseyin Serhat; College of Engineering
    Resonantly driven oscillating MOEMS mirrors have many applications in the fields of optics, telecommunication and spectroscopy. Assuring stable resonant oscillation with well controlled amplitude under varying environmental conditions is a complex task, which can impede or retard incorporation of such MOEMS mirrors in large systems. For this we have developed compact modules comprising optical position sensing and driver electronics with closed loop control, which can ensure stable resonant operation of 1D and 2D micro-mirrors. In this contribution we present in much detail the position encoding and feedback scheme, and show very first experimental results with the novel 2D device.