Numerical calculation of the terahertz field-induced changes in the optical absorption in quantum wells

In the presence of a strong terahertz field, the optical (i.e., valence-to-conduction band) transitions in semiconductors occur between states which are altered by the terahertz field. This alteration has a direct impact on the optical absorption. We describe a numerical technique for calculating the optical absorption in this case by solving the Schrodinger equation for the electron-hole envelope function in real space. This technique correctly accounts for the Coulomb interaction between optically created electron-hole pairs and nonperturbative terahertz-field induced alteration of the states. We applied this technique to investigate the optical absorption of quantum wells of finite width in which terahertz/optical mixing can be significant and which cannot be treated analytically.