Time-domain properties of uniform and non-uniform waveguide long-period gratings

We conduct a detailed theoretical analysis of ultrashort pulse propagation through waveguide long-period grating (LPG) structures operating in the linear regime. We first consider the case of uniform LPGs and we also investigate the impact of the typical grating non-uniformities, e.g. grating profile apodization, and grating period chirping, in the spectral and temporal behaviour of LPG structures. Besides its intrinsic physical interest, our study reveals the strong potential of LPG-based devices for optical pulse re-shaping operations in the sub-picosecond regime.