ABSTRACT
Optical responses of low-dimensional semiconductors are reviewed from a theoretical viewpoint, stressing the electron-hole Coulomb interaction and the excitonic effects. Recent progress of the theoretical studies is highlighted and important problems to be solved are introduced. Dimensionality of the Wannier exciton in particular, is discussed in terms of its linear and nonlinear responses. Theories for a few exciton systems, high-density degenerate electronhole systems, and a Mahan exciton in a one-dimensional metal are also given.
