Publications

Abstract

Thin-film optical coatings are commonly used elements in optical, electrical and architectural applications. Their ability to manipulate the spectral behavior of the light is especially beneficial in fields such as monitoring, sensing and communication. A thin film optical coating is a material layer made of dielectric or conductive material with nano to micrometer level thickness. Distribution of thin-film coating layers with different thickness and materials enable us to obtain optical systems with unique properties which cannot be achieved with a single material. In this work, we intended to develop a novel design tool which can replace commercial software available in the market. Thus, we propose an automated design framework enabling novel product developments for thin-film optical coatings. The goal of the framework is to build an autonomous design and optimization engine which can tailor the spectral response of an optical system by choosing coating materials, layer thicknesses and the number of layers. To do that, a Transfer Matrix Method is built based on a simulation model of the optical films. Then, the simulation model was coupled with the Genetic Algorithm which mimics the biological evolution. For a design objective, we aimed to lower transmission spectra response through the ultraviolet region while keeping the transmission response at the desired value for architectural purposes. Fabrication limitations were defined in collaboration with Turkiye Sise ve Cam Fabrikalari A.S. – Sisecam Science and Technology Center and they were incorporated in design process.

This project is being supported by The Scientific And Technological Research Council of Turkey (TUBITAK) 2209-B Industrial Research Funding Program for Undergraduate Students 2019/1

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@conference{collab3,
  title = {Automated Design Framework for Thin Film Optical Coatings Using Material and Geometry Optimization},
  author = {Z. Arslanturk and A. Sezgin and O. Sayginer},
  year = {2019},
  journal = {Şişecam International Glass Conference Combined With 34th Şişecam Glass Symposium “Glass In The Sustainable Future: Achieving What Is Possible},
  issn = {1431-7907},
  url = {https://collab.sayginer.com/ifofo/abstract-presented-in-sisecam-34th-glass-symposium/}
}

Abstract

Thin film optical filters are key components in optical, electrical and architectural applications. Thanks to their simple and flexible structures, these filters increase their popularity in numerous areas such as monitoring, sensing, communication etc. An optical filter consists of ordered dielectric material layers in the nano-micrometre thickness. Combination of these different layers can bring many superior properties which cannot be achieved with a single material, for instance, quarter-wave stack optical filters are widely used to block light at particular wavelengths. For this reason, the design of thin film structures plays an important role in research activities as well as product development.
In this study, we propose an automated design framework for UV-AR Optical Filters. The optical response of the filters is modeled and simulated using the Transfer Matrix Method. After that, the simulation model is coupled with the genetic algorithm which is a meta-heuristic optimization approach. The design objectives aim at to lower transmission spectra through the ultraviolet region while distributing equal transmission rates through the visible optical region in order to show realistic colors for architectural purposes. In order to achieve this goal, independently distributed material layers are considered for the initial design. Moreover, fabrication constraints are a defined in collaboration with Sisecam Turkey and limitations are taken into account through the design framework.

This project is being supported by The Scientific And Technological Research Council of Turkey (TUBITAK) 2209-B Industrial Research Funding Program for Undergraduate Students 2019/1

Keywords: Thin Film Optical Filters, Transfer Matrix Method, Genetic Algorithm, UV-AR Optical Filters

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BibTeX

@conference{collab2,
  title = {An Automated Design Framework for UV-AR Optical Filters},
  author = {Z. Arslanturk and A. Sezgin and O. Sayginer},
  year = {2019},
  journal = {Nano-optics, Nanophotonics and Nanoplasmonics},
  url = {https://collab.sayginer.com/ifofo/abstract-presented-in-nanotr-15-conference/}
}

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@article{di2019seismic,
  title = {Seismic fragility analysis of a coupled tank-piping system with surrogate modelling and synthetic ground motions},
  author = {di Filippo, Rocco and Abbiati, Giuseppe and Sayginer, Osman and Bursi, Oreste S},
  year = {2019},
  doi = {10.1115/pvp2019-93685}
}

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@conference{collab3b,
  title = {İnce Film Optik Filtreler İçin Otomatize Tasarim Sistemi (in Turkish)},
  author = {Z. Arslanturk and A. Sezgin and O. Sayginer},
  year = {2019},
  journal = {21st National Photonics Workshop (Fotonik ’19),},
  url = {https://collab.sayginer.com/ifofo/abstract-poster-presented-in-fotonik-19-workshop-in-turkish/}
}

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@conference{sayginer2018,
  title = {Er3+ 1-D photonic band gap structure for photonic band edge assisted spontaneous emission enhancement},
  author = {Osman Sayginer and Cesare Meroni and Alessandro Chiasera and Francesco Scotognella and Anna Lukowiak and Giorgio Speranza and Stefano Varas and Lidia Zur and Giancarlo C. Righini and Roberta Ramponi and Oreste Bursi and Maurizio Ferrari},
  year = {2018},
  doi = {10.1016/j.optmat.2018.04.034},
  issn = {0925-3467},
  url = {http://d-photon.fbk.eu/home}
}

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@conference{sayginer2017a,
  title = {Integrated topology optimization of volumetric antenna substrates and conductor surfaces for broadband microstrip patch antennas},
  author = {Osman Sayginer and Gullu Kiziltas},
  year = {2017},
  journal = {Metamaterial Based Designs},
  url = {http://2017apsursi.org/Papers/ViewPapers.asp?PaperNum=1925}
}

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@conference{sayginer2017b,
  title = {Fabrication of functionally graded ceramic- polymer dielectrics via freeze casting for RF applications},
  author = {Osman Sayginer and Gullu Kiziltas},
  year = {2017},
  journal = {Materials and Packaging},
  issn = {0272-9172},
  url = {http://2017apsursi.org/Papers/ViewPapers.asp?PaperNum=2593}
}

Abstract

In parallel to current important developments in electronics and communication technologies, needs on wireless systems have become more popular yet stringent. In order to meet that demand, development of novel technologies and materials has become crucial. Patch antennas are widely used in the radio frequency (RF) industry. This is due to their simple shape, easy and low cost manufacturing capability and their suitability for conformal applications. However, most of current patch antenna designs rely on efforts puts towards their geometrical parameters with limited available dielectric materials in the market. This thesis mainly focuses on the topology optimization of polymer- ceramic composite substrates. These substrates allow for spatial dielectric permittivity variation via their functionally graded multilayer configuration with the objective to achieve minimization of reflected power at desired frequency values. Towards this goal in the proposed optimization study, Comsol Multiphysics 5.2 software was integrated with Matlab 2014b software and genetic algorithm was used as the optimization solver. In addition to the design study, in the second part of the thesis, a cooling system which allows for the adjustment of temperature values between 0℃ and -100℃ was designed to control the substrate properties of functionally graded materials (FGM) of ceramicpolymer antenna substrates, similar to those designed in the first part of the thesis. These substrates were produced via a novel manufacturing method based on freeze casting process. A new test platform was developed in order to investigate the effect of cooling rate and temperature on microporosity and permittivity of these substrate materials.

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@mastersthesis{sayginer2016,
  title = {Topology optimization and cooling system design for functionally graded patch antenna substrates},
  author = {Osman Sayginer},
  year = {2016},
  url = {http://research.sabanciuniv.edu/34797/}
}

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@conference{sayginer2013,
  title = {Resonance frequency analysis of MEMS based on piezoelectric microcantilever beam for vibration energy harvesting applications},
  author = {Osman Sayginer and Ugur Akyol},
  year = {2014}
}

Abstract

Titanium-based and cobalt-chrome alloys have been widely used in orthopaedic applications as these materials can significantly enhance the quality of human life as implant materials. The longevity of these materials is highly influenced by their mechanical properties. In some devices cobalt chrome components articulate with titanium alloy counter faces (e.g. in the taper connections of stems and femoral heads in modern modular designs) and damage has been reported of the harder cobalt chrome by the softer titanium alloy component. This study attempts to understand why this might occur by investigating bulk and surface mechanical properties (such as hardness and Young's modulus) of a number of hip implants and test samples using a Hysitron Triboindenter. AFM images were also obtained to determine the contact area and hence, pile-up correction factors.

The results were compared for samples before being used in the body, to account for surface mechanical response due to implant manufacture, and after, to account for the materials response to long-term cyclic loads. To assess the effects of oxidation, the alloys were treated electrochemically with Sodium-Chloride (NaCl) solution at body temperature. It was found that titanium oxidised preferentially compared with cobalt-chrome alloys. Furthermore, the oxidised titanium showed significantly higher hardness values therefore damaging the un-oxidised cobalt-chrome material. The implications for device design and manufacture are discussed.

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@article{moharrami2013does,
  title = {Why does titanium alloy wear cobalt chrome alloy despite lower bulk hardness: A nanoindentation study?},
  author = {N Moharrami and DJ Langton and O Sayginer and SJ Bull},
  year = {2013},
  journal = {Thin Solid Films},
  doi = {10.1016/j.tsf.2013.06.020},
  issn = {0040-6090}
}