Polarization-dependent terahertz spectroscopy of macroscopic films of aligned single-wall and multiwall carbon nanotubes

The light absorption properties of carbon nanotubes are strongly anisotropic, especially in the terahertz (THz) region of the electromagnetic spectrum due to their inherently one-dimensional intraband carrier dynamics. Macroscopic films of aligned carbon nanotubes are thus ideal for developing high-performance, low-cost THz polarizers. Here, we present results of polarization-dependent time-domain THz spectroscopy studies of large-area films of aligned single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs) in a frequency range of 0.15-1 THz by varying the polarization of the incident beam with respect to the carbon nanotube alignment direction. The nematic order parameter ($S$), the extinction ratio (ER), and the degree of polarization (DOP) were calculated to establish the performance of the films as polarizers. We found the $S$ of the SWCNT film to be 0.96. The ER of the SWCNT was found to be -12 dB. The measured value of the $S$ for the MWCNT was 0.77, with an ER of -11 dB.