The authors propose and demonstrate direct electron-beam writing of surface relief diffractive elements into hybrid inorganic/organic sol-gel glass films. The etch depth and phase delay can be controlled by the electron dose. The potential applications include multi-phase-level diffractive elements and apodised planar waveguide gratings.
Rantala, J., Nordman, N., Nordman, O., Vähäkangas, J., Honkanen, S., & Peyghambarian, N. (1998). Sol-gel hybrid glass diffractive elements by direct electron-beam exposure. Electronics Letters, 34(5), 455-456. https://doi.org/10.1049/el:19980368