Optical control of electron-spin texture based on modulation of spin-orbit interaction in a modulation-doped Ga As / ( Al , Ga ) As quantum well

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We demonstrate the optical control of the spatial spin texture in a modulation-doped Ga As / Al Ga As quantum well based on the modulation of the spin-orbit interaction. Spatiotemporal evolution of electron spins with irradiation by a continuous-wave laser that does not induce interband transitions of electrons reveals an increase in the Rashba coefficient and the spin diffusion coefficient, in contrast to the decrease in these coefficients due to optical doping by increasing the electron-spin excitation density. From the difference between the absorption energy and the emission energy, the carrier density in the quantum well increases. This indicates that the continuous-wave laser irradiation causes photoactivation of naturally deactivated electrons in the doping layer of Al Ga As , and therefore the Rashba spin-orbit interaction increases due to the increased asymmetry of the quantum well profile.