The output polarization of an optically pumped InGaAs/GaAs vertical cavity surface-emitting laser (VCSEL) is analyzed at room temperature as a function of the circular input polarization degree. The emission of the VCSEL is unambiguously controlled by the exciting polarization and only 30% of spin-polarized electrons are needed in the active region to generate an output polarization degree of up to 100% at short-pulsed pumping. This testifies that a VCSEL can be used as an effective amplifier for spin information even at room temperature. Measurements with a continuous wave excitation were executed to demonstrate the possibility of spin-amplification by electrical spin-injection in a VCSEL. All measurements were confirmed by a phenomenological spin flip model. Our paper is completed with the introduction of Fe/Tb-Multilayers used for spin injection. These contacts enable spin injection without external magnetic fields, i.e. in remanence. Finally, we suggest a combination of these multilayers with a VCSEL-structure to create the first spin-optoelectronic device working both at room temperature and without external fields.
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.