Figure 1.

Optically active elementary excitations in semiconductors. (Left) Absorption edge of bulk GaAs at a B = 12 T magnetic field. The lowest energy peaks are caused by excitons strongly distorted by the magnetic confinement. They are followed by Fano-resonances caused by the quantum interference between the second Landau-edge excitons with the one-dimensional continua of the first one. (Right) Resonances associated with confined excitons and Fermi edge singularity in undoped and modulation-doped quantum well structures.