Study of lasing threshold reduction caused by electron spin polarization in the active region of laser diodes

研究了电自旋注入驱动的垂直腔面发射激光器（VCSEL）。重点研究了垂直腔面发射激光器有源区中自旋极化引起的圆极化激射和激射阈值降低。我们研究了在GaAs（110）表面分子束外延生长Fe和FePt层作为自旋注入电极的方法，并对其结构和磁性进行了表征。我们成功地在低温下实现了自旋注入GaAs（110）量子威尔斯阱。然而，观察到的发射的圆偏振度为约5%，这是出乎意料的低。由于GaAs（110）量子威尔斯阱中电子的自旋弛豫时间较长，因此预期会出现高度的圆极化，但没有观察到这种现象。

Vertical cavity surface emitting lasers (VCSELs) driven by electrical spin injection have been investigated. We focused on the circularly polarized lasing and lasing threshold reduction caused by spin polarization in the active region of the VCSELs. We have investigated molecular beam epitaxy growth of Fe and FePt layers on GaAs(110) surfaces for the spin injection electrodes, and characterized the structures and magnetic properties of the layers. We succeeded in the spin injection into GaAs(110) quantum wells at low temperature. However, the degree of the circular polarization of the emission observed was about 5% which was unexpectedly low. A high degree of circular polarization, which was expected because of the long spin relaxation time of the electrons in GaAs(110) quantum wells, was not observed.