Abstract

AC-Stark shifts of the electronic states are observed when a semiconductor is excited by ultrashort, below band-gap laser pulses. So far, all the studies have been performed in undoped samples [1,2], and the effect has been called "excitonic AC-Stark effect". It has been explained by means of the interaction of "virtual" excitons created by the pump beam with the real excitons created by the weak probe beam [3]. In this talk, we will describe our work on the AC-Stark shifts observed in the absorption spectra of modulation doped quantum wells (MDQW). This effect occurs in a new regime, as the absorption edge in MDQW samples at low temperatures is governed by the "Fermi edge singularity" (FES).

© 1993 Optical Society of America