Local Optical Spectroscopy in Quantum Confined Systems: A Theoretical Description

A theoretical description of local absorption is proposed in order to investigate spectral variations on a length scale comparable with the extension of the relevant quantum states. A general formulation, including Coulomb correlation, is derived within the density-matrix formalism and applied to the prototypical case of coupled quantum wires. The results show that excitonic effects may have a crucial impact on the local absorption, with implications for the spatial resolution and the interpretation of near-field optical spectra.