Fig. 1: Scheme of the long-range optical coupling in ENZ materials and the analogy to resonant quantum tunneling.
From: Long-range optical coupling with epsilon-near-zero materials
a Scheme for comparing optical coupling among the ENZ, metallic, and dielectric systems. b Scheme of resonant tunneling through quantum double barriers (E < V0), and the analogy to an optical system composed of two ENZ thin films separated by a dielectric spacer. c Near-zero optical permittivity was observed close to the plasma frequency (λENZ = 1.2 µm) of an ITO thin film from Sigma Aldrich. Measured imaginary part of permittivity is εi = 0.35. d Measured transmission spectra of an ITO thin film (thickness d = 50 nm) fabricated by magnetic sputtering. The ENZ wavelength was indicated by the dip position in the transmission plots measured by Fourier-transform infrared spectroscopy, which is tunable from λENZ = 1.25 µm to λENZ = 1.55 µm by thermal annealing after magnetic sputtering. The input light was under TM polarization.
