Researcher:
Serpengüzel, Ali

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Ali

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Serpengüzel

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    Optical modulation with silicon microspheres
    (IEEE-Inst Electrical Electronics Engineers Inc, 2009) Gürlü, Oğuzhan; N/A; Department of Physics; Yüce, Emre; Serpengüzel, Ali; Master Student; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; 245435; 27855
    In this letter, a silicon microsphere coupled to a silica optical fiber half coupler has been characterized for electrooptical modulation in the L-band at 1.55 mu m. Electrooptical modulation of the transmitted and the 90 degrees elastic scattered signals for both the TE and the TM polarizations of the microsphere resonances has been observed.
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    Resonant channel-dropping filter with integrated detector system based on optical fiber coupler and microsphere
    (IOP Publications, 2004) İşci, Şenol; Yılmaz, Yiğit; Department of Physics; Serpengüzel, Ali; Kurt, Adnan; Bilici, Temel; Faculty Member; Teaching Faculty; N/A; Department of Physics; College of Sciences; N/A; 27855; 194455; N/A
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    Mid-infrared elastic scattering from germanium microspheres
    (IEEE, 2016) N/A; N/A; N/A; N/A; Department of Physics; Zakwan, Muhammad; Bayer, Mustafa Mert; Anwar, Muhammad Sohail; Gökay, Ulaş Sabahattin; Serpengüzel, Ali; PhD Student; Master Student; Master Student; PhD Student; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 27855
    Because of their ultrahigh optical nonlinearities and extremely broad transparency window, germanium microsphere resonators offer the potential for optical processing devices, especially in the mid-infrared (mid-IR) wavelengths. As a semiconductor material for microphotonics applications [1], germanium is particularly attractive owing to its large nonlinearity, high optical damage threshold compared with traditional nonlinear glass materials, and above all, its broad transparency window, extending from the near-IR into the mid-IR. Germanium based optical components have found numerous applications in imaging systems operating in the mid-IR wavelengths, where the principal natural greenhouse gases do not exhibit strong absorption. These applications include rapid sensing and diagnosis [2,] [3], industrial process controls, environmental monitors to hazardous chemical detection [4]. Germanium also is a good electromagnetic shielding material, an attribute that has become increasingly important for modern military applications, where other signals (within the millimeter and centimeter wavelength range) can be strong enough to interfere with nearby IR systems. Elastic light scattering from a germanium microsphere has already been observed in the near-IR [5]. Here, elastic light scattering from a germanium microsphere in the mid-IR region is numerically analyzed using generalized Lorenz-Mie theory (GLMT) [6]. Light interaction with microspheres of various materials is of much interest because of their photonic properties [7]. Germanium has a refractive index of 4, which is even higher than the refractive index of silicon (3.5) in the mid-IR region. The higher refractive index results in higher quality factor morphology dependent resonances (MDRs). A higher value of Q indicates a longer lifetime of the photons trapped inside the cavity and a narrower MDR. Here, the MDRs are observed numerically in the transverse magnetically (TM) and transverse electrically (TE) polarized 90° elastic scattering and 0° transmission for a 40 µm radius germanium microsphere in the mid-IR wavelengths ranging from 5.4 µm to 5.6 µm [8]. The mode spacing of approximately 41 nm between the resonances with the same radial mode order and consecutive polar mode number shows good correlation with the optical size of the germanium microsphere. The germanium microsphere with its high quality factor MDRs can be suitable for optical monitoring and sensing applications in the mid-IR, which require a high spectral resolution [9].
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    Ruby microsphere and liquid cyrstal based tunable optical filter
    (Ieee, 2009) Beccherelli, Romeo; Department of Physics; N/A; N/A; Serpengüzel, Ali; Murib, Mohammed Sharif; Hüseyinoğlu, Ersin; Faculty Member; PhD Student; Master Student; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 27855; N/A
    A microsphere placed in a liquid crystal is used as an optical filter. By changing the refractive index of the liquid cyrstal, the resonance frequency of the sphere is controlled.
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    THz region elastic scattering from a silica microsphere
    (Optica Publishing Group (formerly OSA), 2018) N/A; N/A; N/A; N/A; Department of Physics; Kurt, Suat; Yavuz, Nurperi; Bukhari, Syed Sultan Shah; Serpengüzel, Ali; PhD Student; Master Student; PhD Student; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 27855
    Using generalized Lorenz-Mie theory, we investigated TE and TM polarized 0° transmission and 90° elastic scattering spectra from a silica microsphere with a radius of 200 μm in the Terahertz region from 110 μm to 130 μm. The numerically observed mode spacing of 7 μm agrees well with the theoretically estimated value for both TE and TM polarized WGMs. The observed WGM quality factors are on the order of 104. With these numerically observed spectral responses, silica microspheres can be used in novel THz region applications.
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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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    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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    Amorphous silicon nitride microcavities
    (Optical Soc Amer, 2001) Department of Physics; Serpengüzel, Ali; Faculty Member; Department of Physics; College of Sciences; 27855
    Amorphous silicon nitride microcavities were fabricated by use of distributed Bragg reflectors. The distributed Bragg reflectors were fabricated with alternating layers of quarter-wavelength-thick hydrogenated amorphous silicon nitride and amorphous silicon oxide. The spectral peak of the bulk amorphous silicon nitride photoluminescence spectrum was chosen as the microcavity resonance wavelength. The amorphous silicon nitride microcavity enhances the photoluminescence amplitude and reduces the photoluminescence linewidth with respect to the bulk amorphous silicon nitride. This narrowing and enhancement of the photoluminescence can he understood by the redistribution of the density of optical modes owing to the presence of the microcavity. The microcavity narrowing and enhancement of luminescence in hydrogenated amorphous silicon nitride opens up a variety of possibilities for optoelectronic applications such as resonant-cavity-enhanced light-emitting diodes and color flat-panel displays.
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    Analysis of thermal fields in orthogonal machining with infrared imaging
    (Elsevier Science Sa, 2008) Department of Mechanical Engineering; Department of Mechanical Engineering; Department of Physics; Lazoğlu, İsmail; Serpengüzel, Ali; N/A; Faculty Member; Faculty Member; Department of Mechanical Engineering; Department of Physics; Manufacturing and Automation Research Center (MARC); Manufacturing and Automation Research Center (MARC); N/A; College of Engineering; College of Engineering; College of Sciences; N/A; 179391; 27855
    The validation of a previously developed finite difference temperature prediction model is carried out for orthogonal machining process with a high precision infrared camera set-up, considering the temperature distribution in the tool. the thermal experiments are conducted with two different materials; al 7075, AISI 1050, with two different tool geometries; inserts having a rake angle of 6 degrees and 18 degrees, for different cutting velocities and feedrates. an infrared camera set-up is utilized for the thermal experiments. the results of the high precision infrared thermal measurements are compared with the outputs of the finite difference temperature model, considering the maximum and the mean temperatures in the tool-chip interface zone and the temperature distributions on the tool take face. the maximum tool-chip interface temperature increases with increasing cutting velocity and feedrate. the relationship between the maximum tool-chip interface temperature and the rake angle of the tool is not distinctive. the experimental results show good agreement with the simulations. (c) 2007 Elsevier B.V. all rights reserved.
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    Optics in Turkey
    (Optica Publishing Group, 2009) Department of Physics; Serpengüzel, Ali; Faculty Member; Department of Physics; College of Sciences; 27855
    Koç University, Istanbul, Turkey is playing a key role in leading efforts to advance optics research in the country. The Scientific and Technical Research Council of Turkey (TÜBİTAK) is also playing a key role in supporting these efforts by coordinating research in all disciplines. The country has started participate in the European Commission Framework Program from 2004 to increase collaboration between researchers in Turkey and those in Europe. The university has emerged as one of the major sites for undertaking optics research in the country. Most of the optics research that takes place at the university is conducted in the department of physics and the department of electrical and electronics engineering. The Microphotonics Research Laboratory is another location for conducting experimental research in the field of silicon photonics, microcavity quantum electrodynamics, and laser spectroscopy.