Researcher:
İşçi, Şenol

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Şenol

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İşçi

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İşçi, Şenol

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2003 - 200972010 - 20141

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    Elastic scattering from a sapphire microsphere placed on a silica optical fiber coupler: possible applications to biosensing
    (Springer Heidelberg, 2014) Murib, M. S.; Wagner, P.; N/A; N/A; Department of Physics; Department of Physics; Yılmaz, Yiğit Ozan; Demir, Abdullah; İşçi, Şenol; Bilici, Temel; Kurt, Adnan; Serpengüzel, Ali; Master Student; Master Student; Other; Teaching Faculty; Teaching Faculty; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 194455; 27855
    Elastic light scattering is performed in the original band of optical fiber communication at 1300 nm for a 500 mu m sapphire microsphere placed on a silica optical fiber half coupler. The morphology dependent resonances (MDRs) are observed in the transverse magnetically (TM) polarized and transverse electrically (TE) polarized 0. transmission and 90 degrees elastic scattering obtained from the sapphire microsphere. The TE and TM MDRs can be detected selectively with the use of a Glan polarizer. The TE and TM polarization selectivity provides the ability to select relative MDR to BG levels. The TM polarization provides higher MDR signal to background ratio (SBR) and is suitable for optical monitoring, biological sensing or any other optoelectronic application that requires a high resolution optical filter. The polar angular mode spacing of 0.36 nm of the resonances correlates well with the optical size of the sapphire microsphere. The autocorrelation of the 90 degrees elastic scattering spectra also shows peaks at 0.36 nm. The spectral linewidths of the resonances are on the order of 0.1 nm, which corresponds to quality factors on the order of 10(4.) A sapphire sphere with a radius of 500 mu m and relative refractive index of 1.31, resonances will red-shift by 1.01nm (0.077%). This shift is on the order of 10 linewidths, making sapphire biophotonic sensors an interesting alternative to silica biophotonic sensors.
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    Development of a surgical diode-laser system: controlling the mode of operation
    (Mary Ann Liebert, Inc, 2006) Geldi, Cem; Bozkulak, Ozguncem; Ozgur Tabakoglu, Hasim; Gulsoy, M.; N/A; Department of Physics; İşçi, Şenol; Kurt, Adnan; Other; Teaching Faculty; Department of Physics; N/A; College of Sciences; N/A; 194455
    Objective: The aim of this study was to develop a microcontroller based surgical diode laser system and to test it at two different modes (continuous [CW] and modulated) in vitro on lamb liver tissue. Background Data: In laser surgery, depending on the properties of laser source (wavelength, power, application time, and mode of operation), the effects observed on the tissue may change from carbonization to hyperthermia. The aim is to remove the target tissue without giving any thermal damage to the surrounding tissue. Carbonization should be avoided, thus controlling the mode of operation is very crucial. Methods: The system consisted of a microcontroller based control unit, 980-nm high-power diode laser source, and fiber delivery unit. This system has the capability of delivering different modes of laser energy to the target tissue ranging from CW to 20-Hz modulated beams. The surgical diode laser system was tested on liver tissue in vitro. Efficiency of laser-tissue interaction was quantified in terms of thermal alteration per unit energy and corresponding carbonization level. Results: Modulated mode resulted in larger coagulated area with minimum carbonizations. Carbonized area/thermally altered area (CarbA/TAA) ratio for CW mode of operation at 16 J is 0.35; however, this ratio was found to be 0.05 at modulated mode, when even 10 times higher energy (160 J) was delivered to the target tissue. Conclusion: Results emphasized the significance of mode of operation as well as the other laser parameters. Modulated mode was found to be a promising regime for safer laser surgery.
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    PublicationOpen Access
    Morphology-dependent resonances of optical microsphere resonators for the realization of passive wavelength-division multiplexing components
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2004) Department of Physics; Department of Electrical and Electronics Engineering; İşçi, Şenol; Bilici, Temel; Serpengüzel, Ali; Kurt, Adnan; Faculty Member; Teaching Faculty; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; N/A; N/A; 27855; 194455
    Morphology-dependent resonances of microspheres can provide the necessary optical feedback for applications in spectroscopy, laser science, and optical communications. The elastic scattering of focused light from dielectric microspheres is understood by the localization principle and the generalized Lorenz-Mie theory. We excited the morphology-dependent resonances of glass microspheres by a tunable distributed-feedback laser and detected the elastically scattered signal. Efficient coupling to morphology-dependent resonances is achieved using an optical fiber half coupler. Resonance peaks in the elastic scattering spectra and associated dips in the transmission spectra are observed experimentally. Simulation results of elastic scattering spectra of glass microspheres in the C-band are presented. (C) 2004 Society of Photo-Optical Instrumentation Engineers.
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    PublicationOpen Access
    Microsphere based resonant cavity silicon photodetector
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2004) Department of Physics; Department of Electrical and Electronics Engineering; Serpengüzel, Ali; Bilici, Temel; İşçi, Şenol; Kurt, Adnan; Faculty Member; Teaching Faculty; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; 27855; N/A; N/A; 194455
    Micro Electro Mechanical Systems (MEMS) are among the new and emerging technologies of the future and have many applications in different disciplines. This study presents the dynamic characterization methods that we use to identify the modal parameters of a MEMS device and also the techniques that can be implemented to change the modal parameters. A micro scanner mirror was chosen as the case study to demonstrate the developed methodologies. Initially, the micro mirror was dynamically characterized using experimental modal analysis techniques to identify the modal parameters such as resonance frequencies and mode shapes. Then, it was introduced in a velocity feedback control loop to alter the effective damping of the structure. This method proves to be a very efficient method to alter the modal damping of a micro structure, especially when high quality factors are required for MEMS applications.
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    PublicationOpen Access
    Resonant light coupling to microspheres using Gaussian beams of optical fibers
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2003) Department of Physics; Serpengüzel, Ali; Bilici, Temel; İşçi, Şenol; Kurt, Adnan; Faculty Member; Teaching Faculty; Department of Physics; College of Sciences; 27855; N/A; N/A; 194455
    Morphology dependent resonances of dielectric microspheres are used for polarization insensitive optical channel dropping from an optical fiber half coupler to a silicon photodetector in the M-band. The dropped channels are observed in the elastic scattering and the transmission spectra. The highest quality factor morphology dependent resonances have a repetitive channel separation of 0.14 nm and a linewidth of 0.06 nm. The filter drops approximately 10% (0.5 dB) of the power at the resonance wavelength. The power detected by the photodiode is estimated to be approximately 3.5% of the power in the fiber.
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    PublicationOpen Access
    Microsphere-based optical system for biosensor applications
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2004) Department of Physics; Department of Electrical and Electronics Engineering; İşçi, Şenol; Bilici, Temel; Serpengüzel, Ali; Kurt, Adnan; Faculty Member; Teaching Faculty; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; N/A; N/A; 27855; 194455
    Optical microsphere resonators have been recently utilized in quantum optics, laser science, spectroscopy, and optoelectronics and attracted increasing interest due to their unique optical properties. Microspheres possess high quality factor (Q-factor) optical morphology dependent resonances, and have relatively small volumes. High-Q morphology dependent resonances are very sensitive to the refractive index change and microsphere uniformity. These tiny optical cavities, whose diameters may vary from a few to several hundred micrometers, have resonances with reported Q-factors as large as 3 x 10(9). Due to their sensitivity, morphology dependent resonances of microspheres are also considered for biosensor applications. Binding of a protein or other biomolecules can be monitored by observing the wavelength shift of morphology dependent resonances. A biosensor, based on this optical phenomenon, can even detect a single molecule, depending on the quality of the system design. In this work, elastic scattering spectra from the microspheres of different materials are experimentally obtained and morphology dependent resonances are observed. Preliminary results of unspecific binding of biomolecules onto the microspheres are presented. Furthermore, the morphology dependent resonances of the microspheres for biosensor applications are analyzed theoretically both for proteins such as bovine serum albumin.
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    PublicationOpen Access
    Optical channel dropping using dielectric microspheres
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2003) Department of Physics; Bilici, Temel; İşçi, Şenol; Kurt, Adnan; Serpengüzel, Ali; Teaching Faculty; Faculty Member; Department of Physics; College of Sciences; N/A; N/A; 194455; 27855
    Dielectric microspheres, with their morphology dependent resonances, are used to resonantly couple light from half optical fiber couplers. The dropped channels are observed in the elastic scattering and the transmission spectra. The excitation of the microsphere with the nearly Gaussian beam in the half optical fiber coupler provides spatially and spectrally selective, and enhanced light coupling. The filter drops approximately 10% (0.5 dB) of the power at the resonance wavelength. A tunable single mode distributed feedback diode laser is used as the infrared excitation source. The generalized Lorenz-Mie theory, describing the illumination of the microsphere with a Gaussian beam, is used to interpret the experimental results.
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    PublicationOpen Access
    Resonant cavity enhanced silicon photodetector integrated to a fiber optic coupler
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2003) Department of Physics; İşçi, Şenol; Bilici, Temel; Kurt, Adnan; Serpengüzel, Ali; Teaching Faculty; Faculty Member; Department of Physics; College of Sciences; N/A; N/A; 194455; 27855
    Morphology dependent resonances of dielectric microspheres are used for polarization insensitive optical channel dropping from an optical fiber half coupler to a silicon photodetector in the M-band. The dropped channels are observed in the elastic scattering and the transmission spectra. The highest quality factor morphology dependent resonances have a repetitive channel separation of 0.14 nm and a linewidth of 0.06 nm. The filter drops approximately 10% (0.5 dB) of the power at the resonance wavelength. The power detected by the photodiode is estimated to be approximately 3.5% of the power in the fiber.