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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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    Contrast improvement through a Generative Adversarial Network (GAN) by utilizing a dataset obtained from a line-scanning confocal microscope
    (SPIE, 2024) Department of Physics; Kiraz, Alper; Morova, Berna; Bavili, Nima; Ketabchi, Amir Mohammad; Department of Physics; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Sciences; Graduate School of Sciences and Engineering
    Confocal microscopy offers enhanced image contrast and signal-to-noise ratio compared to wide-field illumination microscopy, achieved by effectively eliminating out-of-focus background noise. In our study, we initially showcase the functionality of a line-scanning confocal microscope aligned through the utilization of a Digital Light Projector (DLP) and a rolling shutter CMOS camera. In this technique, a sequence of illumination lines is projected onto a sample using a DLP and focusing objective (50X, NA=0.55). The reflected light is imaged with the camera. Line-scanning confocal imaging is accomplished by synchronizing the illumination lines with the rolling shutter of the sensor, leading to a substantial enhancement of approximately 50% in image contrast. Subsequently, this setup is employed to create a dataset comprising 500 pairs of images of paper tissue. This dataset is employed for training a Generative Adversarial Network (cGAN). Roughly 45% contrast improvement was measured in the test images for the trained network, in comparison to the ground-truth images.
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    Fundamentals and applications of heat currents in quantum systems
    (Springer Science and Business Media Deutschland GmbH, 2024) Department of Physics; Naseem, Muhammad Tahir; Müstecaplıoğlu, Özgür Esat; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering
    The growing field of quantum thermodynamics has attracted much attention in the last two decades. The possibility of exploiting quantum features in thermal machines led to exciting avenues both from fundamental and application perspectives. For instance, in the presence of non-thermal baths, a quantum heat engine may surpass the classical Carnot limit. On the other hand, heat flow puts severe restrictions on the miniaturization of technologies based on quantum features. It is of paramount importance to look for efficient methods of heat management in the quantum system. One promising direction can be employing heat for powering these devices rather than considering the heat flow as noise. In this chapter, we briefly overview such strategies proposed for efficient heat flow management in the recent past. In particular, we present some of the developments in quantum thermal diodes, thermal transistors, and quantum thermal entanglement machines. In addition, some discussion on the particular models of quantum heat engines and quantum absorption refrigerators is presented. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
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    Photonic materials, architecture, science, and engineering
    (IEEE-Inst Electrical Electronics Engineers Inc, 2023)  ; Department of Physics; Serpengüzel, Ali; Department of Physics;  ; College of Sciences;  
    We review the necessary artistic and scientific fields for the development of any scientific discipline in the history, as well as, in any healthy and contemporary economy. Our case study is photonics, a subfield of electromagnetics, which is undergoing a historical transition from integrated classical photonics to integrated quantum photonics with applications in communication and computation. © 2023 IEEE.
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    Minimizing the focal shift effect on 2D metalenses
    (Institute of Electrical and Electronics Engineers Inc., 2023) Department of Physics; Ramazanoğlu, Serap Aksu; Department of Physics; College of Sciences
    For a metalens, which obeys the fundamental laws governed by diffraction, improving the image quality and resolution at the focal region has been the most valuable and desirable feature [1-3]. Early classical investigations claim that the principal maximum intensity of the diffracted wave is located at the geometric focus, and the field exhibits definite symmetry about the geometrical focal plane. However, with the extended use of lasers it is shown that during the experiments the principal maximum intensity of the incident wave may not occur at the preset geometrical focus butt may be located closer to the lens. This phenomenon is referred as the 'focal shift'. One important detrimental result of the focal shift phenomenon is the asymmetric intensity distribution in the focal region [4-6]. Thus, reducing the focal shift for a better performing metalens is critical as it leads to a symmetric airy disc like field distribution on focal spot. © 2023 IEEE.
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    Concentration dependence of the infrared luminescence efficiencies in TEO-CDCL2 : TM3+ glass
    (Optica Publishing Group, 2003) Özalp, M. Reha; Özen, Gönül; Department of Physics; Department of Physics; Sennaroğlu, Alphan; Kurt, Adnan; Faculty Member; Teaching Faculty; Department of Physics; College of Sciences; College of Sciences; 23851; 194455
    Using exper imental methods, the characteristics of the 1450-nm and 1800-nm luminescence bands of Tm3+ doped TeO2-CdCl2 glasses were studied as a function of the Tm3+ doping level.
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    Minimizing earthquake damage by physical modulation of the soil structure
    (N/A, 2001) Ural, Derin N.; Department of Physics; Serpengüzel, Ali; Faculty Member; Department of Physics; College of Sciences; 27855
    The Bragg scattering phenomenon of solid state physics and photonic crystal concept of optics have been applied to geotechnical engineering to minimize earthquake damage. A theoretical one dimensional wave propagation model is developed and presented. A layered soil profile has been proposed and analyzed. The proposed layered soil profile reflects the incoming waves within the desired design frequency bandwidth.
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    Dynamical properties of a coupled nonlinear dielectric waveguide - surface-plasmon system as a new type of josephson junction
    (IEEE, 2011) N/A; Department of Physics; N/A; Department of Physics; Müstecaplıoğlu, Özgür Esat; Özok, Yasa Ekşioğlu; Güven, Kaan; Faculty Member; PhD Student; Faculty Member; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; 1674; 237974; 52290
    We demonstrate that a weakly-coupled nonlinear dielectric waveguide surface-plasmon (DWSP-JJ) system can be formulated as in analogy to bosonic Josephson junction of atomic condensates, yet the inherently dynamic coupling parameter generates novel features in the phase space.
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    Silicon microspheres for optical modulation applications
    (SPIE-Soc Photoptical Instrumentation Engineers, 2009) Gürlü, Oǧuzhan; Department of Physics; Department of Physics; Department of Physics; Serpengüzel, Ali; Yüce, Emre; Murib, Mohammed Sharif; Faculty Member; Master Student; Master Student; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 27855; 245435; N/A
    A silicon microsphere coupled to a silica optical fiber half coupler is excited using a diode laser operating at 1.55 μm. The transmitted and the 90o elastically scattered light signals are modulated with an electrical square wave applied to the silicon microsphere.
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    Newton-cartan connections with torsion
    (Istanbul Technical University, 2004) Koçak, Şahin; Limoncu, Murat; Department of Physics; Dereli, Tekin; Faculty Member; Department of Physics; College of Sciences; 201358
    We re-formulate the notion of a Newton-Cartan manifold and clarify the compatibility conditions of a connection with torsion with the Newton-Cartan structure.
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    Determination of the stimulated emission cross section from laser-induced pump saturation data in Cr4+-doped solid-state lasers
    (Optical Soc america, 2001) Department of Physics; Department of Physics; Sennaroğlu, Alphan; Yaman, Fatih; Faculty Member; Undergraduate Student; Department of Physics; College of Sciences; College of Sciences; 23851; N/A
    We describe a novel method for the determination of the stimulated emission cross section in Cr4+-doped solid-state lasers from laser-induced pump saturation data. the technique uses the fact that increasing intra-cavity laser intensity stimulates a faster decay of excited atoms and reduces the saturation of pump absorption. a numerical model was developed to analyze the experimental data collected from Cr4+:YaG and Cr4+:forsterite lasers. the best-fit values of the stimulated emission cross section agree with previous results. To demonstrate the applicability of the method to other solid-state lasers, the same technique was also used to determine the emission cross section in a Cr2+:ZnSe laser.