submicrometric alignment of metalenses

In this thesis work we investigate the fabrication of a double face metasurface, which consist in a single silicon substrate with two different metasurfaces, one on the top and one on the bottom. This argument results interesting for the optical branch because of the problems that it solves: one main problem is in fact, the alignment of two optics, which became even harder with meta devices due to their small dimensions. The possibility to combine more optics in one substrate allows to overcome the problem also giving the advantage to have a more compact device. Thanks to an appropriate alignment, the two lenses can work combined allowing to manipulate the infrared light with more degrees of freedom. All the fabrication process is described step by step, starting from the conceptual idea of a metalens, to the characterization of the final sample. We also introduced the simulations needed for the realizations of a metaatom, realized with the software COMSOL, and the simulations of the phase pattern of the device and the propagation of the light with a specific program realized with MATHLAB. The Laboratory procedures followed for achieving the double face metasurface required the usage of different techniques, we used: electron beam lithography, and UV lithography for the realization of the double face. The characterization is then realized in two ways: optically using a scanning electron microscopy for watching the surface and measuring the dimensions of the metaatoms, and with an optical bench to check the correct functioning of the device.