Transduction of the Spin State Variable Between the Electron and Optical Polarization at Zero Magnetic Field

摘要

A New Spin on Electronics: Utilizing the spin degree of freedom of an electron in a semiconductor device is the basis for the emerging field of spin electronics, or spintronics. The idea is that spin-polarized electrons can be introduced into a semiconductor host, and the electron's spin rather than charge can be used as a new state variable to produce performance and functionality not attainable by simply controlling charge motion (as is done in existing devices). To realize this new technology, it is first necessary to get spin-polarized carriers into the semiconductor, and NRL researchers are taking a lead role in this pursuit. Our principal approach has been to electrically inject spin-polarized carriers from an Fe contact into an AlGaAs/GaAs light emitting diode (LED). In this system, we have been able to sustain electron spin polarizations of 40% to 70% in the GaAs. Further, we have uncovered a wealth of information on spin relaxation and transport phenomena through detailed spectroscopic studies. Most recently, we have been able to modify this system so that we can efficiently transduce spin angular momentum from the electrons to the photon optical polarization at zero magnetic field, a key step toward practical device applications such as spin-pumped laser diodes.