Picosecond stimulated photon echo due to intrinsic excitations in semiconductor mixed crystals

Abstract

Time-resolved demonstration of picosecond photon echoes due to intrinsic optical excitations of a semiconductor is presented. Phase relaxation times up to several hundred picoseconds are found for excitons localized by chemical disorder in ${\mathrm{CdS}}_{\mathrm{x}}$ ${\mathrm{Se}}_{1\mathrm{-}\mathrm{x}}$ mixed crystals. These long dephasing times are attributed to reduced scattering of the localized excitons as compared to free excitons. Dephasing is identified as due to energy relaxation of the excitons.