Spin-polarized light-emitting diodes (Spin-LED) consisting of ferromagnetic electrodes, an ultra-thin tunneling
barrier layers and semiconductor LED structure can emit circularly polarized light (CPL) through radiative
recombination of spin-polarized electrons and holes. A lateral-type spin-LED with crystalline AlOx tunnel barrier
layers have been developed for practical applications and have achieved pure CPL emission, electrical helicity
control and CPL detection at room temperature. This article reviews recent progress on spin-photonic devices such
as spin-LEDs and spin-photodiodes and introduces the applications based on CPL.