Description
Surface diffractive optical elements (DOEs) on transparent dielectric materials were fabricated using ultrashort UV laser pulses via direct laser writing. The work focuses on the rapid and flexible fabrication of phase-type DOEs by femtosecond laser surface ablation on glass substrates. Compared to conventional lithographic techniques, the proposed method does not require photomasks or multistep processing and enables significantly faster prototyping. Using a galvanometric scanning system and an optimized multilayer writing strategy, functional four-level phase holograms were fabricated within 25 seconds. The influence of laser parameters, crater overlap, and thermal annealing on surface morphology and diffraction efficiency was investigated. Notably, a maximum diffraction efficiency of 51% was achieved, which closely approaches the theoretical limit of 60% for four-level phase holograms. The results demonstrate that ultrafast UV laser processing is a promising approach for the rapid fabrication of high-quality diffractive optical components for photonics and laser applications.
