Exciton electroabsorption moments and sum rules

Excitonic electroabsorption spectra in semiconductor epilayers and heterost ructures have spectral structure that contributes to modulator performance in broad-band applications such as femtosecond pulse manipulation. We defin e several electro-optic sum rules and electroabsorption moments combined in to figures-of-merit that describe field sensitivities, bandwidths and signa l-bandwidth products for semi-insulating GaAs heterostructures and AlGaAs/G aAs multiple quantum wells. The quantum-confined Stark effect and Franz-Kel dysh field ionization are treated on an equal basis in the analysis. Franz- Keldysh field broadening produces larger electroabsorption than the quantum -confined Stark effect in quantum wells for electric fields smaller than 40 kV/cm. (C) 2000 Elsevier Science B.V. All rights reserved.