Ultrafast time-resolved quantum beats in the polarization state of coherent emission from quantum wells

Abstract

Dual-channel spectral interferometry is used to measure the ellipticity, the orientation of the polarization ellipse, and the sense of rotation of the four-wave-mixing signal from a GaAs-AlGaAs multiple quantum well. Each is observed to oscillate dramatically at the heavy-hole-light-hole quantum beat frequency. During each beat period (in the strong quantum beat regime), the ellipticity oscillates twice between linear and almost circular polarization, the orientation of the polarization ellipse rotates through a complete 180°, and the sense of rotation changes from left to right circular polarization.