High-field terahertz time-domain spectroscopy of single-walled carbon nanotubes

We experimentally demonstrated the high-field THz response of Single-Walled Carbon Nanotubes (SWCNT) in the broad frequency range from 0.2 to 2.0 THz. To investigate the impact of nanomaterial geometry on the absorption of THz radiation, two kinds of SWCNT films with different diameters and lengths were fabricated. The measured conductivity shows the change that can be attributed to the change of the Drude term of conductivity. This in-crease in conductivity at lower frequency was described either as the increase in the number or decrease in effective masses of free charge carriers different for two samples. Our study suggests that the conductivity of the SWNTs in strong THz fields is enhanced by inducing strong non-linear electron dynamics as a result of several competing processes. Our findings can be used to predict the behavior of CNT devices (modulators, polarizes, lenses, etc.) in the THz high-field.