Optical fiber–Ta2O5 waveguide coupler covered with hydrophobic zeolite film for vapor sensing

by  T. Babeva,A. Andreev,J. Grand,M. Vasileva,E. Karakoleva,B.S. Zafirova,B. Georgieva,J. Koprinarova, S. Mintova


•Fiber optic coupler covered with highly hydrophobic MFI-type zeolite film was investigated.
•The optical response of coupler was predicted by theoretical modeling and confirmed experimentally.
•The application of coupler for vapor sensing was demonstrated.
•The advantages of both fiber optic sensors and spin-on zeolite films as selective medium were combined.


Coupler comprising side-polished optical fiber and tantalum pentoxide (Ta2O5) waveguide coated with 330 nm hydrophobic MFI-type zeolite films was utilized as chemical sensor for acetone vapors. The thickness of the zeolite films was selected through theoretical modeling of the resonant wavelength shift in order to achieve the highest possible sensitivity. The spectral positions of the resonances were determined through solving of the characteristics equations for the coupled waveguides and finding their mode effective refractive indices. The optical quality of the coupler surface, that is responsible for the proper operation of the device, was controlled through 3D optical imaging prior to and after deposition of the zeolite films. The application of side-polished optical fiber–Ta2O5 waveguide coupler covered with hydrophobic zeolite film for acetone vapor sensing was demonstrated and discussed.

Graphical abstract

Image for unlabelled figure


  • side-polished optical fiber;
  • distributed coupler;
  • zeolite film;
  • chemical sensors;
  • optical sensing
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