Abstract
We measured the transmission of THz time domain spectroscopy of four different types carbon nanotubes(pristine multi-wall, single-wall nanotubes, impurity multi-wall, and single-wall nanotubes ).According to our results, there’s no absorption obviously in 0.2~2 THz region, but the conductivity of impurity nanotubes is higher than pristine nanotubes. We also have measured optical pump-THz probe experiment for different type nanotubes. According to these measurements, there are two different mechanisms, which is exhibits two different scattering times explained by Drude model. Another 800 pump-probe experiment which is a photoreflectivity (PR) setup will show here. From our data, we found the negative relaxation phenomenon clearly. The negative signals of PR exaplain by Photobleaching (PB).