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Article Citation - WoS: 35Citation - Scopus: 35Invisible Thin-Film Patterns With Strong Infrared Emission as an Optical Security Feature(Wiley-v C H verlag Gmbh, 2018) Bakan, Gokhan; Ayas, Sencer; Serhatlioglu, Murat; Elbuken, Caglar; Dana, AykutluSpectrally 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 - WoS: 7Citation - Scopus: 7Colorimetric Detection of Ultrathin Dielectrics on Strong Interference Coatings(Optical Soc Amer, 2018) Ayas, Sencer; Bakan, Gokhan; Ozgur, Erol; Celebi, Kemal; Torunoglu, Gamze; Dana, AykutluMetal 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 America
