A Moire technique is used in the fabrication of a diffractive phase mask by electron beam lithography. The phase mask has a varying diffraction efficiency designed to produce apodised fibre Bragg gratingswith a uniform ultraviolet beam exposure. Since the illumination is uniform, the average induced refractive index is constant along the grating and pure apodisation results.

Electronics Letters
Department of Electronics

Albert, J, Hill, K.O., Johnson, D.C., Bilodeau, F., & Rooks, M.J. (1996). Moire phase masks for automatic pure apodisation of fibre Bragg gratings. Electronics Letters. doi:10.1049/el:19961469