THE METHOD OF DETECTING INHOMOGENEITIES AND DEFECTS IN MATERIALS USING SENSORS BASED ON THE FIBER BRAGG OPTIC STRUCTURES

The article presents the possibilities of detecting defect in materials using the fiber Bragg gratings (FBG). Steel belts with a thickness of 1 mm were used for the tests: one standard and the others were damaged. The damage was in the form of incisions. The FBG was glued to the sample with epoxy glue along its entire length and elongation by outside force. Based on the transmission spectrum obtained on the Optical Spectrum Analyzer (OSA) the processing characteristics: the main minimum on the transmission characteristics, total width of the spectrum and the full width at half maximum FWHM depending on the FBG strain was determine.

Оптические свойства многослойных пленочных структур BaTiO-=SUB=-3-=/SUB=-/SiO-=SUB=-2-=/SUB=-, сформированных золь--гель-методом

Multi-layer film structures BaTiO_3/SiO_2 with a thickness of ~1 μm containing up to 14 pairs of layers were synthesized by the sol–gel method with sequential heat treatment. It is shown that the synthesized structures are X-ray amorphous. The formation of bands in the transmission and reflection spectra caused by interference effects is demonstrated. A more regular structure exhibits a photon band gap (opacity band) in the visible range with main minimum at 636 nm and corresponding maximum in the reflection spectra. Dispersion characteristics of barium titanate films with different concentrations of initial sols were studied and an increase in the refractive index with an increase in the concentration of sol was demonstrated. For a sol with a concentration of 60 mg/mL, the refractive index in the spectral range of 390–1600 nm is 1.88–1.81. The prospects of sol–gel technology for the formation of BaTiO_3/SiO_2 structures for nanophotonics and solar radiation converters are discussed.