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An all-dielectric route for terahertz cloaking

An original all-dielectric design that performs cloaking at terahertz frequencies is demonstrated. The cloak consists of radially positioned discretized micrometer-sized cylindrical elements. Based on Mie theory and under adequate excitation conditions (H along the rod axis), high-κ cylinders exhibit a strong magnetic resonance dependent on the cylinder radii and material properties. Full-wave simulations coupled with a field-summation retrieval technique were employed to adjust the electromagnetic response of individual ferroelectrics rods (Ba0.5Sr0.5TiO3; ε = 200 - tan δ = 2.10-2). The rods magnetic plasma frequency was engineered such that the full cloak displays a progressive variation in its permeability radial component; hence satisfying, for this polarization, the reduced equations derived from the conformal transformation theory. The cloaking performance was assessed by modelling the complete micro-structured device. Results unambiguously show that cloaking of any wavelength scaled objects located inside the cloak is achieved above the Mie resonance frequency at 0.58 THz for the present device. In particular, the phase fronts of the electric field behind the device are well reconstructed with a high value in transmission of the incident plane wave. This also means that the absorption losses are small within the cloak in comparison with the metallic systems originally proposed. Although cloaking is observed in a narrow band, this all-dielectric configuration provides an attractive route for designing cloaking devices at microwave and terahertz frequencies.