  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.
