Article

Optical and Quantum Electronics

, Volume 38, Issue 8, pp 655-665

Deposition of coatings on long-period fiber gratings: tunnel effect analogy

  • I. Del VillarAffiliated withDepartamento de Ingeniería Eléctrica y Electrónica, Universidad Pública de Navarra Email author 
  • , I. R. MatiasAffiliated withDepartamento de Ingeniería Eléctrica y Electrónica, Universidad Pública de Navarra
  • , F. J. ArreguiAffiliated withDepartamento de Ingeniería Eléctrica y Electrónica, Universidad Pública de Navarra

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Abstract

The sensitivity of Long-period fiber gratings (LPFGs), coated with high-refractive-index thin film overlays, to the refractive index and the thickness of the overlay, and to the ambient refractive index, can be enhanced with a design based on a two-overlay coating of an LPFG. The first overlay of lower refractive index than the cladding affects the guidance of a cladding mode in the second overlay of higher refractive index than the cladding. This causes a more abrupt cladding modal redistribution than with the deposition of a unique high-refractive-index overlay. The phenomenon is analyzed with a method based on a vectorial analysis of modes and the application of coupled mode theory.

Keywords

gratings coupled-mode analysis thin films optical fiber sensors