Fig. 2: DM structure and design.
From: High-security learning-based optical encryption assisted by disordered metasurface
a A TiO2 unit meta-pillar of the DM with designed parameters is arranged in a square lattice on a fused silica substrate. b The simulated phase delays of the meta-pillar for two orthogonally linear polarizations (along x and y directions) versus lengths of the two axis of the DM. c Seven different polarization states between the LCP and RCP are defined by tuning the fast axis of QWP in the setup (Fig. 3a) and the recorded speckles corresponding to the 7 polarization states. d Speckle PCC versus polarization of incident beam, with the speckle associated with incident LCP as the reference. e Top (left) and perspective (right) views of SEM images of the fabricated DM. The scale bar in (e) is 1 mm. DM disordered metasurface, PCC Pearson’s correlation coefficient, RCP right-handed circular polarization, LCP left-handed circular polarization.
