Browsing by Author "Aydemir, Umut"

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    50 GHz, 100 fs pulses at 100 W average power from a burst mode, all-single mode, Yb-doped fiber laser system
    (EDP Sciences, 2024-10-18) Laçin, Mesut; Repgen, Paul; Maghsoudi, Amirhossein; Şura, Aladin; Aydemir, Umut; İlday, Fatih Ömer; Michailovas A.; Mackenzie J.I.; Pirzio F.; Cormier E.
    We present a uniquely simple laser integrated in strictly single-mode fibers, producing bursts of 100-fs pulses at 50 GHz repetition rate at 100 W average power. This allows material processing with high efficiency and precision in the ablation-cooled regime.
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    ANN-based estimation of MEMS diaphragm response: An application for three leaf clover diaphragm based Fabry-Perot interferometer
    (Elsevier BV, 2022-06-23) Yigit, E.; Hayber, Ş. E.; Aydemir, Umut
    In this study, an artificial neural network (ANN) based model is developed for MEMS diaphragm analysis, which does not require difficult and time-consuming FEM processes. ANN-based estimator is generated for static pressure response (d) and dynamic pressure response (f) analysis of TLC (three leaf clover) diaphragms for Fabry-Perot interferometers as an example. TLC is one of the unsealed MEMS design diaphragms formed by three leaves of equal angles. The diaphragms used to train ANNs are designed with SOLIDWORKS and analyzed with ANSYS. A total of 1680 TLC diaphragms are simulated with eight diaphragm parameters (3 for SiO2 material, 4 for geometry, and 1 for pressure) to create a data pool for ANN’s training, validation, and testing processes. 80% of the data is used for training, 15% for validation, and the remaining for testing. Only four geometric parameters are used as input in the ANN estimator, and the material parameters are added to the model with an analytical multiplier. Thus, network models that estimate d and f values for all kinds of diaphragm materials are proposed, with a material-independently trained ANN structure. The performance of the ANN model is compared with the empirical equation suggested in the literature, and its superiority is demonstrated. In addition, the d and f parameters of TLC diaphragms designed with five different materials (Si, In2Se3, Ag, EPDM, Graphene) are estimated to be very close to the real ones. By using the proposed method, analyses of TLC diaphragms are quickly performed without the need for time-consuming and costly design and analysis programs.
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    Degrading effect on electrical properties of printed gallium sulfide based photodetector
    (Institute of Physics Publishing Ltd., 2024-05-24) Odacı, Cem; Khan, Muhammad Shaukat; Jose, Manoj; Kisielewska, Marta; Roshanghias, Ali; Aydemir, Umut
    Layered GaS structures have been attracting increasing research interest due to their highly anisotropic structural, electrical, optical, and mechanical properties. However, the investigation of the performance based on the responsivity, external quantum efficiency, and detectivity of printed GaS based photodetector on a flexible PET substrate with respect to a period of time under the environmental conditions have not been reported so far. This experimental study shows that the printed GaS based photodetector stored in ambient conditions undergoes a change in terms of performance in a few weeks after the fabrication. This work also holds an importance being premier study experimentally investigating the printed III–VI group monochalcogenide based photodetector stored under the environmental conditions and contributing the literature to improve the printed device performance in further applications.
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    Design and simulation of a novel fungus-shaped center embossed diaphragm for fiber optic pressure sensors
    (Elsevier, 2020-12-19) Hayber, Ş. E.; Aydemir, Umut
    A novel structure with a fungus-shaped center embossed diaphragm (FCED) geometry has been proposed to modify in diaphragm-based Fabry-Perot fiber optic pressure sensors (FP-FOPS). The proposed FCED geometry was obtained by adding a pillar between the mesa and diaphragm. Before the simulation analysis of FCED, we derived mathematical equations of attenuation factor widening the acceptance radius. The attenuation factor is defined to understand sensor loss, which is neglected in the literature. With this derived formula, the light reflected from the deflected diaphragm and the light unguided in the fiber was detected. Since the deformation angle is zeroized in the FCED structures, the sensor loss due to the attenuation factor is eliminated. All the incident light being re-guided in the fiber. With FCED design’s help, the decreasing sensitivity in the center embossed diaphragms (CED) has been prevented. Moreover, the deviation of the frequency response of FCED remains lower than 1% compared with the results of conventional diaphragms. As a result, it produces a more stable sensor, and the FCED structure is less affected by manufacturing errors. The researchers can benefit from the use of our presented results when designing and producing new diaphragm-based FP-FOPS.
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    Enhanced photoresponse of PVP:GaSe nanocomposite thin film based photodetectors
    (Institute of Physics Publishing Ltd., 2022-02-21) Demirtaş, T.; Odacı, C.; Aydemir, Umut
    Two-dimensional materials have become the focus of attention of researchers in recent years. The demand for two-dimensional materials is increasing day by day, especially with the inadequacy of graphene in optical applications. In this context, the optical and electrical characteristics of the PVP:GaSe thin film nanocomposites were investigated. The surface morphologies of the samples were characterized by SEM, the thin film thicknesses and refractive index parameters were measured by the Ellipsometer method, the structural characteristics were obtained by XRD, and Raman and PL spectroscopy was used to determine the optical characteristics. Critical parameters of Au/PVP:GaSe/n-Si photodetector were calculated under various illumination intensities. It is observed that photodetector with PVP:%5GaSe thin film has the best performance results. According to the experimental results, its responsivity, external quantum efficiency, and detectivity values are 0.485 A W−1, %86, and 1.14 × 107 cm Hz1/2 W−1 respectively.
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    Fabrication and characterization of printed phototransistors based on monochalcogenide inks
    (American Chemical Society, 2023-04-04) Odacı, C.; Muehleisen, W.; Aydemir, Umut; Roshanghias, A.
    Two-dimensional (2D) layered semiconductors of Group-III monochalcogenides have gained increasing attention in photonics and electronics. The fabrication of large-scale, inexpensive inks which can be used in printed electronics applications is facilitated by the solution processing of 2D materials. In this study, gallium sulfide (GaS)-, gallium selenide (GaSe)-, and gallium telluride (GaTe)-loaded inks were synthesized and implemented to fabricate phototransistors on SiO2\Si substrates. To explore the printed device performances, several color illuminations were applied to the printed phototransistor, and the mobility, photoresponsivity, and external quantum efficiency parameters were compared. Under red-light illumination, the mobility of a GaTe nanoparticle-based phototransistor reached 7.456 cm2 V-1 s-1. The responsivity of the GaTe-based phototransistor was found to be the highest, with the value of 9.52 A W-1 under green light illumination. However, GaSe-based phototransistors gave the highest EQE value of 2482 (%) under blue light illumination with the mobility of 7.04 cm2 V-1 s-1. This study demonstrates that printable Group-III monochalcogenide inks can be synthesized with desired properties for use in printed electronic applications.
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    The enhanced lifetime of printed GaS-based photodetectors with polymer encapsulation
    (Elsevier BV, 2024-12-02) Odacı, Cem; Khan, Muhammad Shaukat; Beduk, Tutku; Jose, Manoj; Kisielewska, Marta; Aydemir, Umut; Roshanghias, Ali
    Exhibiting excellent absorption in the UV-visible wavelength range makes layered gallium sulfide (GaS) semiconductor material a promising candidate for use in electronics and optoelectronics applications. Recently, a fully printed GaS-based photodetector has been proposed and fabricated, rendering a low-cost fabrication process in flexible electronics. However, the degradation of the semiconductor layer due to environmental conditions causes reliability issues and shortens their lifetime. Thus, in this study, an attempt has been made to encapsulate printed GaS-based photodetector using different polymers to hinder the degradation. It is demonstrated that encapsulating the printed GaS-based photodetector by utilizing the polymer-capping method with styrene copolymers, Polystyrene-block-polyisoprene-block-polystyrene, highly hydrogenated poly(styrene)-block-poly (butadiene), partially hydrogenated poly(styrene)-block-poly(butadiene), increases the performance of the photodetector. The efficiency of the GaS-based photodetector printed on flexible polyethylene terephthalate (PET) substrate has reached up to 123 % in responsivity in 6 weeks after the polymer coating. Also, the device figure of merit, the detectivity value of the printed photodetector, has increased more than three times after the polymer coating compared to its as-deposited state. Meanwhile, it is observed that the fall and rise times of the printed GaS photodetector have remained constant. Based on these results attained in this study, it can be claimed that the polymer coating provides high performance and long stability in the printed GaS-based photodetectors on flexible substrates, which will pave the way for the further implementations of III-VI group layered semiconductor materials in electronics and optoelectronics applications.