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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6

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Department: search.filters.department.Department of Electrical and Electronics EngineeringIndexed at: search.filters.indexed.TR Dizin

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    PublicationOpen Access
    Photonic integrated circuit-assisted optical time-domain reflectometer system
    (TÜBİTAK, 2022) Department of Electrical and Electronics Engineering; Onbaşlı, Mehmet Cengiz; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 258783
    Optical time-domain reflectometers (OTDR) are photonic systems that consist of an interrogator, a receiver and a fiber optical cable and have applications in telecommunications, security, environmental monitoring, distributed temperature and strain sensing. Since OTDR systems are bulk optical setups that consume multiple Watts of power, have large mass and volume footprint and are vulnerable to thermal drift, deployment of OTDR systems in the field is expensive, complicated and may not necessarily yield accurate sensing results. Thus, a compact, low-power, inexpensive and thermal drift-free OTDR system needs to be developed for improving the accuracy and the viability of OTDR in the field. In this study, I present the design and modeling of a photonic integrated OTDR system design based on IMEC's iSiPP50G silicon integrated photonic process design kit. The photonic integrated circuit includes a photonic modulator and a photodetector. Photonic power link budgets and the corresponding electronic signal-to-noise ratios are analyzed for 5-110 km fiber optical OTDR systems and power-efficient OTDR system designs are presented for inexpensive multiproject wafer fabrication.
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    PublicationOpen Access
    Genetic algorithm-driven surface-enhanced Raman spectroscopy substrate optimization
    (Multidisciplinary Digital Publishing Institute (MDPI), 2021) Yanık, Cenk; Department of Electrical and Electronics Engineering; N/A; Onbaşlı, Mehmet Cengiz; Bilgin, Buse; Torun, Hülya; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; Graduate School of Sciences and Engineering; 258783; N/A; N/A
    Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive and molecule-specific detection technique that uses surface plasmon resonances to enhance Raman scattering from analytes. In SERS system design, the substrates must have minimal or no background at the incident laser wavelength and large Raman signal enhancement via plasmonic confinement and grating modes over large areas (i.e., squared millimeters). These requirements impose many competing design constraints that make exhaustive parametric computational optimization of SERS substrates pro-hibitively time consuming. Here, we demonstrate a genetic-algorithm (GA)-based optimization method for SERS substrates to achieve strong electric field localization over wide areas for recon-figurable and programmable photonic SERS sensors. We analyzed the GA parameters and tuned them for SERS substrate optimization in detail. We experimentally validated the model results by fabricating the predicted nanostructures using electron beam lithography. The experimental Raman spectrum signal enhancements of the optimized SERS substrates validated the model predictions and enabled the generation of a detailed Raman profile of methylene blue fluorescence dye. The GA and its optimization shown here could pave the way for photonic chips and components with arbitrary design constraints, wavelength bands, and performance targets.