LAUSR

Circular dichroism (CD) of a doped carbon nanotube is calculated as a function of wavelength for several values of the Fermi energy. In the calculation of CD, we consider the so-called depolarization effect by taking account of the dielectric function that suppresses or enhances the electric field inside the undoped or doped nanotube, respectively. Because of the induced electric current of the carriers, the CD of a doped carbon nanotube becomes much larger than that of an undoped nanotube when we select the light-propagating direction parallel to the nanotube axis. The sign of CD changes for enantiomer pair of nanotubes or for type-I and type-II semiconductor nanotubes or by changing the Fermi energy, which is useful for identifying nanotubes in the device.