Fig. 1. Bending of an electromagnetic wave while passing from one medium to another with different refractive indices. An electromagnetic wave traveling at an angle of α1 with respect to the normal in a medium with a refractive index η1 undergoes refraction at the medium interface and travels at an angle of α2 with respect to the normal in a medium with a refractive index η2.

Fig. 2. Dispersive (Re P) and absorptive (Im P) parts of polarization versus detuning of radiation frequency from midpoint between levels b′ and b. The polarization is plotted on an arbitrary scale, and detuning Δ is plotted in units of atomic decay. Inset, upper right-hand corner: usual dispersion-absorption curve. Inset, upper left-hand corner: present level scheme. Reprinted with permission from Ref. [5], copyright by the American Physical Society.

Fig. 3. Schematic of the metal film with periodic slits. The parameters are defined as in the figure: a is the width of the slit, d is the periodicity, and L is the thickness of the metal film. The black regions indicate the metal parts, and the white regions are the vacuum. The film is extended in the x-y plane. Reprinted with permission from Ref. [31], copyright by the American Physical Society.

Fig. 4. Metal surface with periodic holes drilled (above) and equivalent waveguide structure (below). Reprinted with permission from Ref. [36], copyright by the AIP Publishing.

Fig. 5. (a) Unit cell of metal cubes that were arranged in a cubic array fashion; all the six surfaces of these cubes consisted of air slits and were interconnected by three orthogonal wires along with the simplified structure (left) with two plates with air slits and a connecting wire along the z direction. Reprinted with permission from Ref. [40], copyright by the American Physical Society. (b) A layered view of bulk materials formed with a unit cell of single cut wire on a dielectric substrate. (c) An I-shaped metallic patch structure. (d) A terahertz metamaterial with Z-shaped meta-atoms.

Fig. 6. Ultrathin terahertz metamaterial with a double-sided metal structure depicting a deep subwavelength coupling absence (above) and presence (below) between the metal structures situated on both sides of an ultrathin dielectric substrate. Reprinted with permission from Ref. [50], copyright by the AIP Publishing.