Ensemble spin coherence of singly charged InGaAs quantum dots

Abstract

This Chapter reviews experimental and theoretical studies of electron spin coherence in singly-charged (In,Ga)As quantum dots. Ultrafast optical technique, the pump-probe Faraday rotation, is used for generation and control of the spin coherence. Despite the ensemble inhomogeneity the electron spin coherence time T2 is measured in the mode-locking regime of synchronization of the electron spin precession about external magnetic field with the periodic laser excitation. This synchronization effect is enhanced and stabilized by electron-nuclear hyperfine interaction allowing frequency focusing of the inhomogeneous electron ensemble into the single precession mode. Ultrafast optical spin rotation of resident electrons in quantum dots to any point on the Bloch sphere is demonstrated and all-optical spin echo for these electrons is realized.