Optical and Terahertz Response of Carbon Nanostructures

In the last three decades or so, we have witnessed an extraordinary progress in the research and technology of carbon-based nanomaterials. Among the peculiar highlights are the discoveries of fullerene, the carbon nanotubes and the magnificent simple scotch tape exfoliated graphene. The unique photophysical properties of these different allotropic forms of the nanocarbon have opened up vast application possibilities in many fields of science and technology, with particular emphasis on optoelectronics and photonics. A prerequisite for many of these applications is a thorough understanding of the nature of the elementary and coupled excitations and also various dynamical processes involving them. Here, we present an overview of the recent excitement with the carbon nanostructures, in particular, the quantum dots, nanotubes and graphene. We discuss some of their very interesting properties investigated through optical and THz spectroscopic tools. At optical frequencies, the light emitting properties, the nonlinearities and ultrafast response have been presented, while, the low-energy response has been considered in terms of studies obtained by using THz time-domain spectroscopy. Finally, we conclude with some of the future prospects on the photophysics of carbon nanosystems in realistic applications.