Spin-controlled LEDs and VCSELs

Abstract

We investigate the dependence of the polarization of an optically pumped vertical-cavity surface-emitting laser (VCSEL) on the degree of electron spin polarization in the active region at room temperature. We show that the output polarization of the laser can be unambiguously controlled by the pump polarization even with low spin polarizations. Less than 30% electron spin polarization in the active region is enough to achieve 100% output polarization of the VCSEL. The dependence of the polarization of the VCSEL emission on the degree of electron spin polarization in the active region is investigated at room temperature. Electrical spin injection via ferromagnetic contacts into LED structures has been shown to be possible with efficiencies close to ten percent at room temperature. We suggest to combine ferromagnetic contacts with VCSELs because the nonlinearity of the laser at threshold can potentially be used to convert small spin injection efficiencies into a large effect onto the degree of polarization of the emitted light.