Design and fabrication of bifunctional metalenses

Regarding light beams, an interesting feature is the spatial distribution of their wavefront. In fact, the wavefront of light beams can be engineered to obtain a precise shape through the local modification of the phase of the electromagnetic wave. This process is known as light structuring and can be realized through the use of dedicated optics. The most popular light structuring feature is the generation of helicoidal wavefronts, with the presence of the so called vortex singularity, which provide light with orbital angular momentum (OAM). This task can be achieved through the use of metalenses, flat nanostructured devices. A particular type of metalens are called dual-function metalenses that can manage of two distinct spin states. This multiple functionality is possible due to the specific structure of the meta-units, each containing a nanofin with different shape and orientation. The aim of this thesis work is the design, fabrication and characterization of this spinmultiplexing metalens. The device is realized in silicon.The design process is carried out through the meta-units simulation with finite element method analysis. The fabrication is performed in nanofabrication facility. The device behaviour is then characterized by laser illumination and the quality of the intensity pattern was evaluated. Among its applications, this device has a potential for telecommunication purposes in quantum regime level and contrast phase microscopy.