Yazar "Gökhan, Fikri Serdar" seçeneğine göre listele

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    Analysis and simulation of forcing the limits of thermal sensing for microbolometers in CMOS-MEMS technology
    (Mdpi, 2019) Göktaş, Hasan; Gökhan, Fikri Serdar
    Room-temperature highly sensitive microbolometers are becoming very attractive in infrared (IR) sensing with the increase in demand for the internet of things (IOT), night vision, and medical imaging. Different techniques, such as building extremely small-scale devices (nanotubes, etc.) or using 2D materials, showed promising results in terms of high sensitivity with the cost of challenges in fabrication and low-noise readout circuit. Here, we propose a new and simple technique on the application of joule heating on a clamped-clamped beam without adding any complexity. It provides much better uniformity in temperature distribution in comparison to conventional joule heating, and this results in higher thermal stresses on fixed ends. This consequently brings around 60.5x improvement in the overall temperature sensitivity according to both theory and COMSOL (multiphysics solver). The sensitivity increased with the increase in the stiffness constant, and it was calculated as 134 N/m for a device with a 60.5x improvement. A considerable amount of decrease in the operation temperature (36x below 383 K and 47x below 428 K) was achieved via a new technique. That's why the proposed solution can be used either to build highly reliable long-term devices or to increase the thermal sensitivity.
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    Analytical approach of Brillouin amplification over threshold
    (Optical Soc Amer, 2018) Gökhan, Fikri Serdar; Göktaş, Hasan; Sorger, Volker J.
    We report on an accurate closed-form analytical model for the gain of a Brillouin fiber amplifier that accounts for material loss in the depleted pump regime. We determined the operational model limits with respect to its relevant parameters and pump regimes through both numerical and experimental validation. As such, our results enable accurate performance prediction of Brillouin fiber amplifiers operating in the weak-pump, high-gain, and saturation regimes alike. (C) 2018 Optical Society of America
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    Analytical approach of brillouin fiber amplifier gain up to 2 km long fibers
    (2020) Gökhan, Fikri Serdar
    In order to obtain analytical gain expression in Brillouin optical Fiber Amplifiers (BFAs), coupled intensity equations describing the interaction of pump and stokes waves must be solved simultaneously. For long optical fibers, although fiber loss is responsible for the pump depletion and nonnegligible effect, for short optical fibers less than 2 km, its effect can be discarded. In this paper, we provide an accurate analytic expression for the BFA gain for fiber lengths less than 2 km by discarding the optical fiber loss and show results of experimental validation.
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    Analytical approach to calculate the gain of Brillouin fiber amplifiers in the regime of pump depletion
    (Optical Soc Amer, 2019) Gökhan, Fikri Serdar; Göktaş, Hasan
    We provide an accurate analytic expression for the Brillouin fiber amplifiers (BFAs) gain in the regime of pump depletion. The solutions are divided into three parts. In the first part, we review the weak pump regime where the highly accurate second-order corrected undepleted-pump-approximation-based solution is adopted; in the high-gain regime where both the fiber loss and nonlinear term are nonnegligible effects and need to be accounted for along with the pump depletion; and in the saturation regime where the Stokes power is at the rear end exceeds critical power. We provide an accurate analytic expression for the BFA gain and show results of experimental validation. The presented analysis can be used to accurately predict the performance of Brillouin fiber amplifiers working in any regime. (C) 2019 Optical Society of America
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    Electrical-driven plasmon source of silicon based on quantum tunneling
    (Amer Chemical Soc, 2018) Göktaş, Hasan; Gökhan, Fikri Serdar; Sorger, Volker J.
    A silicon-based light source presents an unreached goal in the field of photonics due to silicon's indirect electronic band structure preventing direct carrier recombination and subsequent photon emission. Here, we utilize inelastically tunneling electrons to demonstrate an electrically driven light emitting silicon-based tunnel junction operating at room temperature. We show that such a junction is a source for plasmons driven by the electrical tunnel current. We find that the emission spectrum is not given by the quantum condition where the emission frequency would be proportional to the applied voltage, but the spectrum is determined by the spectral overlap between the energy-dependent tunnel current and the modal dispersion of the plasmon. By coupling an internal electric field enhancement with an external k-vector matching grating, we were able to demonstrate a 10-fold increase in the internal efficiency and a 40-fold increase in overall quantum efficiency. Such an electron tunneling-based mechanism could lead to a new class of solid-state light sources with unique features such as down-scalability and temporal responses that are significantly shorter than that of light-emitting diodes.