Precision laser recording of microstructures on molybdenum films for generating a diffractive microrelief

We discuss a problem of reducing the thickness of lines of the contact pattern masks produced by laser ablation of thin films of refractory metals and used when synthesizing the micro-relief of diffractive optical elements (DOEs). For a contact mask for a DOE on molybdenum, patterns with features in the range 0.25-0.3 $µ$m were recorder by laser ablation on 40-nm thick films. This is approximately 3 times smaller than the characteristic dimensions obtained by thermochemical recording chromium films of the same thickness in the standard process. A microrelief of height of up to 300 nm was formed in a quartz substrate by reactive ion etching in an inductively coupled plasma through the mask. We show that thin molybdenum films can have promising applications as metallic masks when synthesizing a DOE microrelief.