Metal-coated long period gratings for detection of corrosion

Abstract

In this paper, the long period grating (LPG) with a metal outer clad is analyzed. The transfer constant of core mode and cladding mode were derived from numerical method. The complex refractive index of the metal outer clad make the transfer constant to be a complex number. The imaginary part of the transfer constant is representing the loss during the wave's transmission. Theoretical analysis shows that the core mode's loss caused by metal clad is can be ignored when the radius of the clad is 62.5um. The complex refractive index make larger resonance wavelength shift than the refractive index without imaginary part.