Browsing by Author "Ayas, Sencer"
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Article Citation Count: 8Colorimetric detection of ultrathin dielectrics on strong interference coatings(Optical Soc Amer, 2018) Bakan, Gökhan; Bakan, Gokhan; Ozgur, Erol; Celebi, Kemal; Torunoglu, Gamze; Dana, Aykutlu; Department of Electrical & Electronics EngineeringMetal films covered with ultrathin lossy dielectrics can exhibit strong interference effects manifested as the broad absorption of the incident light resulting in distinct surface colors. Despite their simple bilayer structures, such surfaces have only recently been scrutinized and applied mainly to color printing. Here, we report the use of such surfaces for colorimetric detection of ultrathin dielectrics. Upon deposition of a nanometer-thick dielectric on the surface, the absorption peak red shifts, changing the surface color. The color contrast between the bare and dielectric- coated surfaces can be detected by the naked eye. The optical responses of the surfaces are characterized for nanometerthick SiO2, Al2O3, and bovine serum albumin molecules. The results suggest that strong interference surfaces can be employed as biosensors. (C) 2018 Optical Society of AmericaConference Object Citation Count: 0Infrared Absorption Spectroscopy of Monolayers with Thin Film Interference Coatings(Ieee, 2017) Bakan, Gökhan; Bakan, Gokhan; Ozgur, Erol; Celebi, Kemal; dana, Aykutlu; Department of Electrical & Electronics EngineeringWe report high performance Infrared spectroscopy platforms based on interference coatings on metal using CaF2 dielectric films and Ge2Sb2Te5 (GST) phase-change films. IR vibrational bands of proteins and organic monolayers are also detected.Article Citation Count: 28Invisible Thin-Film Patterns with Strong Infrared Emission as an Optical Security Feature(Wiley-v C H verlag Gmbh, 2018) Bakan, Gökhan; Ayas, Sencer; Serhatlioglu, Murat; Elbuken, Caglar; Dana, Aykutlu; Department of Electrical & Electronics EngineeringSpectrally selective thermal emission is in high demand for thermophotovoltaics, radiative cooling, and infrared sensing applications. Spectral control of the emissivity is historically achieved by choosing the material with suitable infrared properties. The recent advancements in nanofabrication techniques that lead to enhanced light-matter interactions enable optical properties like infrared emissivity that are not naturally available. In this study, thermal emitters based on nanometer-thick dielectrics on field-enhancement surfaces as optical security features are proposed. Such a function is achieved by generating patterns by ultrathin dielectrics that are transparent in the visible and exhibit strong infrared absorption in the spectral range of thermal cameras. The invisible patterns are then revealed by thermal imaging. The field-enhancement surfaces enhance the emissivity of the patterns, in turn reduce the minimum temperature to detect the thermal emission down to approximate to 30 degrees C from >150 degrees C to exploit ubiquitous heat sources like the human body. The study provides a framework for the use of thermal emitters as optical security features and demonstrates applications on rigid and flexible substrates.Article Citation Count: 7Tunable enhanced infrared absorption spectroscopy surfaces based on thin VO2 films(Optical Soc Amer, 2018) Bakan, Gökhan; Ayas, Sencer; Dana, Aykutlu; Department of Electrical & Electronics EngineeringInfrared absorption spectroscopy takes advantage of the electric field enhancement to detect low amounts of materials such as monolayer biomolecules. While the plasmonic field enhancement is the popular approach, it has been demonstrated that the interference-based uniform field enhancement using a simple dielectric/metal structure exhibits higher sensitivity and larger spectral bandwidth for ultrathin materials. Here, we numerically demonstrate that the enhancement bandwidth of such interference coatings can be further increased by inserting a VO2 thin film between the dielectric and metal layers. The field enhancement spectrum blueshifts upon thermally-induced insulator-to-metal transition in the VO2 layer. The structure that maximizes the enhancement bandwidth is determined as 880-nm-thick CaF2 on 350-nm-thick VO2 on optically thick Al. The study is completed with the investigation of using a bottom metal layer as an internal heater to electrothermally induce the phase change. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement