Femtosecond laser direct writing of annular binary phase mask in glasses

3D printing of optical functions creates new perspectives by allowing the fabrication of lenses or components that combine several functions, thereby simplifying and compacting optical systems. These recent developments have become possible thanks to the emergence of additive 3D printing processes that use nano‑doped polymers or glass. Another approach consists in modifying the material’s structure with a femtosecond laser. Both approaches enable the creation of complex (freeform) phase gradients either on the surface or by modifying the material’s refractive index. These methods differ from traditional approaches that rely on material ablation and therefore offer a more environmentally friendly solution. In this presentation, we will apply laser‑writing techniques to fabricate annular phase masks designed to increase the depth of focus of optical systems. These phase masks will be produced in different materials (Corning 9754, EagleXG, Infrasil301, SuprasilCG). Phase delays of +π or –π have been implemented. The masks have been experimentally evaluated against their counterparts made by photolithography. A camera with a phase mask placed at its pupil visualizes a scene containing objects at various distances. A qualitative analysis of the images shows a similar level of blur in the depth of field between laser-structured masks and those fabricated by photolithography.