Rouard's method modeling of type I-IR fiber Bragg gratings made using an ultrafast IR laser and a phase mask

Rouard's method is used to model the spectral response of type I-IR gratings. Type I-IR gratings are shown to have a broader bandwidth and larger sideband suppression than would be expected from standard type I UV-written gratings. These properties are related to the nonlinear dependence of the index change on intensity. At higher intensities the spectral response indicates saturation of the index change growth rate.