Tunable deflection and asymmetric transmission of THz waves using a thin slab of graphene-dielectric metamaterial, with and without ENZ components

Abstract

Tunable deflection of obliquely incident, linearly polarized terahertz waves is theoretically studied in a wide frequency range around 20 THz, by combining a thin slab of graphene-dielectric metamaterial (with ten layers of graphene), a dielectric grating, and a uniform polar-dielectric slab operating in the epsilon-near-zero (ENZ) regime. The modulation of the deflection intensity and deflection angle is done by varying the chemical potential of graphene, and is realized with or without connection to the asymmetric transmission. It is shown to depend on the location of the graphene-dielectric metamaterial slab, as well as on the incidence angle. Four scenarios of tunable deflection are found, including the ones realizable in two-component structures without an ENZ slab.

Dynamic chiroptical responses in transmissive metamaterial using phase-change material

“…Therefore, active optical metamaterials with controllable properties are in great demand [1]. In order to meet the requirements, many studies have been focused on tunable metamaterials by incorporating tunable mechanisms or materials within their subwavelength unit cells, including semiconductors [2][3][4][5][6][7], PIN diodes [8], twodimensional materials [9][10][11][12][13][14], and phase change materials (PCMs) [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Ge 2 Sb 2 Te 5 (GST) acts as an important component of PCMs will exhibit tremendous optical contrast when they experience a phase transition between the amorphous and crystalline states, resulting from distinct bonding mechanisms in two states.…”

VO2-hBN-graphene-based bi-functional metamaterial for mid-infrared bi-tunable asymmetric transmission and nearly perfect resonant absorption

“…Breaking the spatial inversion symmetry [1,2] and the time reversal symmetry [3,4] are two approaches that can be employed to achieve a strong forward-to-backward transmission contrast for an optical system. For the former case, the transmission of nonpolarized and circularly/linearly polarized light through a device is Lorentz-reciprocal and can be realized in diverse structures, such as waveguides [8], chiral/achiral metamaterials [1,9,10], metallic gratings with/without slits [5,6,11,12], metamaterials based on hyperbolic hole arrays [13], and graphene-based metamaterials [14][15][16][17]. Moreover, the combination of diffraction or subwavelength gratings with one-or two-dimensional photonic crystals [2,18,19] and hyperbolic metamaterials (HMMs) [20] can also lead to the observation of AT.…”

Tunable infrared asymmetric light transmission and absorption via graphene-hBN metamaterials

“…34 Recently, considering effective parameters of a multilayer graphene-dielectric metamaterial in the calculations, dynamical tuning of AT was demonstrated at frequencies around 20 THz. 35 Another category of these artificial structures is multilayer graphene-hexagonal boron nitride (hBN) metamaterials (GhMMs) that consist of alternating layers of graphene and hBN. 36,37 hBN is a uniaxially anisotropic material that shows hyperbolic characteristics in the MIR range while acting as a dielectric medium at FIR frequencies.…”