Laser patterning of SiOx-layers for the fabrication of UV diffractive phase elements

Diffractive phase elements (DPE), consisting of a patterned UV-transparent layer on a UV-transparent substrate, were fabricated by three steps. A UV-absorbing SiOx-coating (x < 2) with a thickness matching to the required phase delay was deposited on a fused silica substrate. The coating was removed on a pixel array corresponding to a calculated two-dimensional quantized phase function (DPE-design). By a thermal annealing process the SiOx-coating was oxidised to UV-transparent SiO2, resulting in a UV-grade surface relief element.