Broadband extraordinary terahertz transmission through super-aligned carbon nanotubes film.

We experimentally demonstrate the extraordinary transmission of THz waves through super-aligned multi-walled carbon nanotube (MWCNT) films with one-dimensional arrays of sub-wavelength rectangular gratings in the broad frequency range from 0.2 to 2.5 THz. To achieve this, two kinds of MWCNT films (1 μm and 3 μm in thickness) were fabricated by drawing from a sidewall of super-aligned nanotube arrays synthesized by low pressure chemical vapor deposition. The measured complex refraction index of the film exhibits highly anisotropic transmission of THz waves through the MWCNTs. The anisotropy depends not only on the polarization direction of the THz waves but also on the orientation of the MWCNT gratings. We found that the resonantly extraordinary THz transmission originated from the surface plasmon polaritons supported by periodically patterned carbon nanotube gratings. Our experimental results may provide important insights for emerging THz plasmonic devices based on carbon nanotubes.