Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 1Citation - Scopus: 1Experimental Demonstration of a Transient Grating Controlled All-Optical Switch(IOP Publishing, 2023) Akın, Osman; Dinleyici, Mehmet SalihWe demonstrate an on-fiber all-optical switching device based on a transient grating formed by the interference of control laser pulses in a Kerr-type nonlinear material placed in the evanescent region of the fiber. The device can operate in two distinctive modes. First, switching/coupling among the fiber modes using bulk index modulation was investigated and an efficiency of about %0.55 @852 nm was measured. Second, by exploiting Four Wave Mixing (FWM), an all-optical switching that transfers power among light signals with wavelengths of λ 1 = 440 nm and λ 2 = 663 nm was achieved by quasi-phase-matching and fRequency matching in a nonlinear thin polymeric film. The results prove that the introduced switching structure may have the potential to be used in integrated photonic applications such as intensity modulators or controllable couplers.Article Citation - WoS: 5Citation - Scopus: 5Nanoscale Curved Dielectric Film Characterization Beyond Diffraction Limits Using Spatially Structured Illumination(Academic Press, 2020) Ataç, Enes; Dinleyici, Mehmet SalihOptical fiber based sensor systems often utilize thin dielectric films coated on non-planar surfaces are needed to be inspected for quality assurance. However, non-destructive optical characterization of these films is not a simple method especially on curved large surfaces. In this study, we propose a real time procedure to estimate the optical properties of sub-wavelength transparent dielectric films coated on optical fibers. The paper includes developing a mathematical model and its experimental verification. The near field phase diffraction method is combined with the structured light illumination that is spatial modes of optical fibers to estimate the thickness of the phase object beyond the classical diffraction limits. Numerical simulations and experimental results show that the film thickness can safely be characterized up to one tenth of wavelength of interest via selective spatial field distribution determined according to the morphology of the thin film. The outcomes have good agreements with destructive Scanning Electron Microscope (SEM) measurements. © 2020 Elsevier Inc.Article Citation - WoS: 2Citation - Scopus: 2Investigating the Experimental Limits of the Brewster’s Angle Method(Türkiye Klinikleri Journal of Medical Sciences, 2018) Sümer, Can; Kuştepeli, Alp; Dinleyici, Mehmet SalihWe present the method, analysis, and experimental results of the Brewster’s angle method commonly used for determining the refractive indices of optical films. We show the significance of the intersection of reflectance curves, in that the necessity for substrate refractive index and film layer thickness knowledge are both eliminated. We present the conditions for the existence of the second intersection of reflectance curves and introduce a method for determining the refractive index of the substrate layer by using the angular information alone. Analytical results reveal impressive practical sensitivity and accuracy limits for the method, where the experimental results also support the theoretical analysis.Article Citation - WoS: 7Citation - Scopus: 7Demonstration of Pulse Controlled All-Optical Switch/Modulator(The Optical Society, 2014) Akın, Osman; Dinleyici, Mehmet SalihAn all-optical pulse controlled switch/modulator based on evanescent coupling between a polymer slab waveguide and a single mode fiber is demonstrated. Very fast all-optical modulation/switching is achieved via Kerr effect of the nonlinear polymer placed in the evanescent region of the optical fiber. Local refractive index perturbation (δn = -1.45612 × 10 -5) on the thin film leads to 0.374 nW power modulation at the fiber output, which results in a switching efficiency of ≈1.5%.Article Citation - WoS: 5Citation - Scopus: 7A Practical Approach for Optical Characterization of a Film Coated on the Optical Fiber(Academic Press Inc., 2017) Ekici, Çağın; Dinleyici, Mehmet SalihPhase Diffraction (PD) Phase Diffraction. which is a result of the interaction of light waves with a transparent object, is exploited to characterize precisely optical properties of dielectric films coated on the optical fiber without harming any feature of the sample. Typical fiber sensor applications require films coated on the side surface of the optical fiber and optical properties of that curved films are crucial for design purposes. In this study, three Polyvinyl Alcohol (PVA) films are prepared, their thicknesses are estimated based on the phase diffraction method by fitting experimental results with a mathematical model within 2.3% error. The outcomes of this practical method show good agreement with findings of the destructive Scanning Electron Microscopy (SEM) measurements. The method has the potential to allow real time monitoring abrupt changes of surrounding medium's properties and to examine coating quality (i.e. thickness uniformity) of the film.Conference Object Kırınım Yöntemi Kullanılarak Zeytinyağındaki Tağşişin Belirlenmesi(Institute of Electrical and Electronics Engineers Inc., 2017) Ekici, Çağın; Dinleyici, Mehmet SalihBu çalışmada, faz kırınım yöntemi kullanılarak gıda sanayisindeki büyük sorunlardan biri olan zeytinyağındaki tağşişin belirlenmesi amaçlanmıştır. Örnek sıvı içerisine ideal geometriye sahip fiber optik batırılarak lazer ışığının kırınımı incelenmiştir. Kırınım alanının matematiksel ifadesi Fresnel kırınım teorisine göre nümerik olarak hesaplanmıştır. Matematiksel modelleme, deneyler sonucunda elde edilen normalleştirilmiş kırınım deseniyle karşılaştırılıp, sıvının kırıcılık indisi tahmin edilmiştir. Kırınım yönteminin sıvının kırıcılık indisi tahminindeki yüksek hassasiyetli rolü (10−5 mertebesindeki) zeytinyağındaki tağşişin belirlenmesine imkan sağlamıştır.Article Citation - WoS: 8Citation - Scopus: 10Design of Dual-Mode Dual-Band Photonic Crystal Bandpass Filters for Terahertz Communication Applications(John Wiley and Sons Inc., 2015) Karakılınç, Özgür Önder; Dinleyici, Mehmet SalihIn this study, Photonic Crystal (PhC) dual-mode dual-band bandpass filter is designed and its transmission characteristics are investigated for various configurations. PhC resonator structure is formed by a point defect microcavity that is equipped with one large and three smaller auxiliary perturbation rods. Degenerate modes at each band may also be excited by changing the structure properties of the perturbation. Plane wave expansion method and Finite Difference Time-Domain method are used to analyze the device characteristics. Proposed dual-band dual-mode PhC filter structure can effectively be used for terahertz communication applications.Article A Fiber-Integrated Optical Component Fabricated Via Photopolymerization: Mode-Selective Grating Coupler(Elsevier Ltd., 2013) Sümer, Can; Dinleyici, Mehmet SalihWe demonstrate a mode-selective directional coupler based on a grating structure, which is fabricated by laser direct-writing on a photopolymer thin film. The device is implemented on the flat planar surface of the D-Fiber, enabling fiber integration, where an Acrylamide/Polyvinyl Alcohol based photopolymer material is used in the fabrication of the device. While the refractive index modulation properties of the polymer material are well known, surface relief and corrugation properties due to photopolymerization are investigated in this study. Theoretical model of the device is presented together with the optimization and simulation results of the final device; experimental results have been found to be in good agreement with simulations.Article Citation - WoS: 1Citation - Scopus: 1Interference Grating Structures in Photonic Crystal Circuits(Springer Verlag, 2011) Karakılınç, Özgür Önder; Dinleyici, Mehmet SalihPhotonic Crystal Circuits have been widely investigated for various optoelectronics device applications. And the gratings in photonics devices are indispensable tool, which is very common for light manipulation. In this study, an interference grating structure formed by Gaussian beam interferences in photonic crystal waveguide such that having Kerr type nonlinearity is proposed and its transmission characteristics are investigated. Finite-Difference Time-Domain method is used to analyze the device characteristics. According to simulation results, the interference grating has shown special transmission characteristics that can bring tunability for photonic crystal devices. This can be an effective method for controlling optical signals in the photonic crystal for all optical switching/routing applications as a part of add/drop multiplexing.Article Citation - WoS: 8Citation - Scopus: 8Characterization and Estimation of Refractive Index Profile of Laser-Written Photopolymer Optical Waveguides(Elsevier Ltd., 2011) Dinleyici, Mehmet Salih; Sümer, CanIn this study, channel waveguides fabricated in photopolymer films by direct-writing using a low-power CW laser, are used as phase objects in a simple plane-wave diffraction setup, and the refractive index modulation profiles of the waveguides are characterized using the recorded diffraction patterns. Index profiles are modeled by piece-wisely combining two Gaussian functions representing the central and the tail regions. Measured diffraction patterns are matched with patterns generated using the model. This simple model makes it possible to design various channel waveguides embedded into polymer substrates. The proposed model is tested on three distinctive waveguide profiles written on the same Acrylamide/Polyvinyl Alcohol based photopolymer with different exposures.