Bulg. J. Phys. vol.43 no.3 (2016), pp. 233-242



Porous One-Dimensional Photonic Crystals for Color Sensing of Vapors and Liquids

T. Babeva
Acad. J. Malinowski Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 109, 1113 Sofia, Bulgaria
Abstract. One-dimensional photonic crystals are artificial structures, where refractive index varies periodically in one direction. Unlike Bragg stacks, they are characterized with omnidirectional reflectance, i.e high reflectance for all incidence angles and polarizations of light. Thus they are very suitable for utilization as color indicators of liquids and vapors, because the change of the color will be exclusively due to the presence of analyte, not to the change of viewing angle. In the present study, chalcogenide glasses (GeSe2) and sol-gel metal oxides (Ta2O5 and V2O5) are used as high refractive index material providing sufficient optical contrast, while zeolite and polymer (PMMA) films are employed for sensitive materials with low refractive index that change their optical properties or thicknesses upon exposure to analyte. Selective optical detection of acetone and chloroform based on monitoring of color change is demonstrated and discussed.

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