Terahertz radiation from coherent confined optical phonons in GaAs/AlAs multiple quantum wells

We have investigated the characteristics of the intense terahertz (THz) electromagnetic radiation in (GaAs)35/(AlAs)35 multiple quantum wells with an optical gating method, where the radiation source is coherent longitudinal optical (LO) phonons confined in the GaAs layers. It is found that the intensity of the THz wave from the coherent GaAs‐like LO phonon is enhanced under the condition that the pump‐pulse energy is resonant with the energies of the confined heavy‐hole and light‐hole excitons, which suggests the considerable contribution of the Fröhlich interaction to the generation mechanism. The period‐number dependence of the THz‐wave intensity demonstrates that the THz wave generated in each GaAs layer is constructively superimposed. Moreover, the temperature dependence of the THz‐wave intensity is discussed from an aspect of disturbance by thermal phonons. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)