Experimental Investigation of Three‐Level Optical Stark Effect in Semiconductors

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Abstract
The three‐level optical Stark effect is due to a dynamical coupling of two excited levels. The coupling is achieved by a high intensity CO2 laser. Results of experiments on multiple quantum wells (MQW) and excitons in Cu2O are presented. In the MQW the coupling between the two lowest conduction band sublevels leads to characteristic changes in the one‐photon spectra of the lowest exciton transitions. In Cu2O the CO2 laser pulse couples 1 S and 2 P excitons. In this case the one‐photon spectrum of the 2 P exciton (dipole allowed) and also of the 1 S spectrum (quadrupole allowed) show drastic changes. Most of the experimental results can be explained quantitatively in terms of a nonlinear susceptibility.