Study On Characteristics Of Fiber Bragg Grating With Ideal-metal Material Cladding

A fiber Bragg grating with ideal-metal material (real dielectric constant is negative) cladding is proposed in this paper. First, eigenvalue equations withnegative dielectric constant are solved with numerical method. In this way, relations between value of effective index n_eff and values of fiber core-material index n_co and cladding-material index n_cl belonging to fundamental modes of the ordinary guided mode and surface-plasma-wave (SPW) are obtained. The reflectivity r is calculated by using the coupled-mode theory , especially reflectivities belonging to different periodicities A while keeping its length L , core redius a , fiber core-material index n_co and cladding-material index n_cl . The results indicate that for these two different modes of this kind of fiber, the values and the relations between fiber core-material index n_co and cladding-material index n_cl have corresponding impact on the effective indexn_eff. This kind of fiber Bragg grating has favorable filter characteristic, the periodicity A can lead to the variation of reflectivity range which is not in the reflectivity bandwidth. The reseach results provide an important theoretic basis fornew application of fiber Bragg grating in filter technology.