Abstract
The coupling of a photon probe to electron-hole magnetoplasmas in quantum wells is calculated for the first time including electron-hole pairing and excitonic effects. Optical experiments on modulation-doped quantum wells support the validity of the mean-field approximation involved. The condensation of quasi-two-dimensional, neutral, electron-hole plasmas into an excitonic-insulator state is accompanied by strong modifications of magneto-optical spectra. Significant magnetic field and well-width dependences on dynamical Stark effect and exciton saturation are predicted.