Abstract

Recently, the observation of spin quantum beats in time-resolved photoluminescence after picosecond excitation of GaAs quantum wells (QWLs) was reported.[1] A semiclassical description of this novel experiment follows: The circularly polarized laser generates an electron spin polarization in z direction according to the transition rules (Fig. 1). The magnetic field in the perpendicular x-direction forces these spins into a Larmor precession around the x direction, i.e., the electron spin polarization changes periodically with the Larmor frequency between parallel and antiparallel to the z direction. As a consequence, light emitted in z direction periodically oscillates between the two circular polarizations. A typical example is shown in Fig. 2 for a high quality 25nm QWL with an inhomogeneous broadening of the heavy-hole exciton line of 300μeV. [1]

© 1995 Optical Society of America