The Influence of Phase Mask Stitch Errors on the Performance of UV-written Bragg Gratings

Bragg gratings produced by direct UV exposure are finding wide-spread applications in fields ranging from telecommunications to optical sensing. In order to produce such fibre gratings a great deal of research has been directed to the use of electron beam lithography for direct writing of the phase masks [1]. The technique allows very precise structures (grating period < 100 nm) to be defined over large areas up to 140 × 140 mm2. Phase mask are generated by stitching small (400 μm x 400 μm) electron beam fields together. It is therefore important to understand the nature of the various stitching errors which can occur and their effect on the corresponding UV written fibre grating spectra. Here we report the spectroscopic effect of one sign stitching errors which has the characteristic of shifting the grating in a field to one direction (left or right) only along the grating axis.