Light-induced dielectric transparency in single-walled carbon nanotube films

Light-induced difference THz spectroscopy was used to investigate the dielectric response of free-stand single-walled carbon nanotubes (SWCNTs) films in THz region. We observed an enhanced transmission of the peak-signal of THz wave through SWCNTs films under 800 nm pump. In frequency domain, the transparency came from 0.5 to 2.1 THz and the absorption was in 2.1-3.0 THz region. The pump power dependency of the transmission showed this was a nonlinear effect. The dielectric constant response of the SWCNTs films was analyzed theoretically. The analysis suggests that the nonlinear optical properties stem from two factors, which are Drude and Lorentz term for metallic and semiconducting SWCNTs, respectively.