Influence of fringeless UV post-exposure on index modulation amplitude in fiber Bragg gratings

摘要

Dynamics of the refractive index modulation amplitude during uniform UV post-exposure of fiber Bragg gratings at 248 nm are examined. The change in index modulation amplitude depends on the strength of the grating prior to the post-exposure and also on the degree of zero-order suppression in the phase mask used to write the grating. Furthermore, during the post-exposure, diffraction orders are observed emanating from the fiber in the absence of a phase mask. This observation is incorporated into the development of a model that successfully explains the post-exposure dynamics.