Barcode encryption based on spin hall effect in tunable vertical hyperbolic metamaterial

In this work, we present a novel vertically hyperbolic metamaterial vHMM structure comprising multilayer stacks of titanium nitride TiN-alumina Al2O3 films. Based on the modulation of the parallel permittivity ɛ∥ and vertical permittivity ɛ⊥ of the vHMM structure by the filling ratio of TiN in the vHMM structure and incident wavelength, we theoretically design and analyze three epsilon-near-zero ENZ structures to investigate the spin Hall effect of light SHEL. Our results demonstrate that all three ENZ structures exhibit significant enhancement of SHEL, with the lateral shift exhibiting extreme sensitivity to the incident angle and producing micron-level variations within a few milliradians. Notably, the class-II of ENZ structure ɛ∥≠0,ɛ⊥≈0 suffers from the highest loss and yields the weakest enhancement of SHEL. Furthermore, we discover that the sign of the transverse shift of the SHEL can also be modulated according to the filling ratio of TiN in the vHMM structure and incident wavelength within a specific incident angle. Based on the regulation law, we propose two barcode encryption schemes that exploit the traverse directions. Our study provides a new mechanism for practical applications of SHEL in optical communication and data storage.