Magnetic-Field-Induced Spin-Conserving and Spin-Flip Intersubband Transitions in InAs Quantum Wells

Intersubband optical resonances in InAs/AlSb quantum wells have been studied in the Voigt configuration. Both spin-conserving and spin-flip transitions in the midinfrared spectral range were observed simultaneously. We demonstrate that the in-plane magnetic field mediates the spin-conserving transitions, whereas the bulk inversion asymmetry of InAs induces spin-flip excitations. The difference in the observed resonance energies allows us to deduce directly the depolarization shift. Moreover, we show that this depolarization strongly reduces the linewidth of the spin-conserving resonance.