Broadband Generation of Polarization-Immune Cloaking via a Hybrid Phase-Change Metasurface

Terahertz tunable vanadium dioxide metasurface for dynamic illusion and cloaking

Realizing camouflage by illusion and cloaking based on the metasurface has received widespread attention recently. However, existing metasurface-based illusion and cloaking devices are valid for the incident wave with a specific frequency, angle, or polarization, or exhibit a single function. Therefore, a terahertz tunable vanadium dioxide (VO2) metasurface carpet cloak is proposed for dynamic illusion and cloaking. Simulation results show that by controlling the state of the VO2, the metasurface carpet cloak can simultaneously achieve illusion and cloaking functions, working at 0.45 THz and 0.6 THz, and is effective for orthogonal circularly polarized waves with different incidence angles. That is the function, frequency, incident angle, and polarization of the metasurface carpet cloak are dynamically adjustable. Besides, the metasurface carpet cloak is robust to the incident angle and is capable of polarization angle stability. This work has potential value in the real-life application of metasurface-based illusion and cloaking devices.

Revealing a one-dimensional optically cloaked surface using the spin Hall effect of light

The realization of an optical cloak that can hide a target object is no longer fiction, yet distinguishing the optically cloaked surface from our illusion remains an open problem. Here, the detection of a one-dimensional optically cloaked surface is presented by leveraging the spin Hall effect of light, the microscopic and transverse splitting of linearly polarized light at an optical interface into two circular polarizations. We first derive an analytical formula for the spin Hall shift at a planar surface with a linear phase gradient and demonstrate that the spin Hall effect of light at the cloaked surface differs from that at its perceived image. The theoretical description and numerical computation are generalized for a curved surface with a nonlinear phase gradient. Two approaches for examining optically cloaked surfaces are presented, in which the unknown incident angle and phase gradient are successfully reproduced. This work suggests the potential of the spin Hall effect of light in various applications, including anti-counterfeiting and security.