Theory of the two-photon Franz-Keldysh effect and electric-field-induced bichromatic coherent control

When a strong electric field is applied to a semiconductor, acceleration of charge carriers modifies the optical absorption spectrum. This phenomenon, the Franz-Keldysh effect, is the basis of photoreflectance spectroscopy and electroabsorption modulators. The authors extend here a theory of the Franz-Keldysh effect and calculate field-induced changes in the two-photon absorption spectrum and a related coherent control process. Results of numerical calculations for gallium arsenide predict a strong polarization dependence and absorption changes that depend on the sign of the field.