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Spin induced gigahertz polarization oscillations in vertical-cavity surface-emitting laser devices

Ackemann, Thorsten and Li, M. Y. and Jaehme, H. and Soldat, H. and Gerhardt, N.C. and Hofmann, M. R. (2011) Spin induced gigahertz polarization oscillations in vertical-cavity surface-emitting laser devices. In: Vertical-Cavity Surface-Emitting Lasers XV. Proc. SPIE, 7952 . UNSPECIFIED, 79520B.

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Abstract

Spin-controlled vertical-cavity surface-emitting lasers (VCSELs) have been intensively studied in recent years because of the low threshold feasibility and the nonlinearity above threshold, which make spin-VCSELs very promising for spintronic devices. Here we investigate the circular polarization dynamics of VCSELs on a picosecond time scale after pulsed optical spin injection at room temperature. A hybrid excitation technique combining continuous-wave (cw) unpolarized electrical excitation slightly above threshold and pulsed polarized optical excitation is applied. The experimental results demonstrate ultrafast circular polarization oscillations with a frequency of about 11 GHz. The oscillations last inside the first undulation of the intensity relaxation oscillations. Via theoretical calculations based on a rate equation model we analyze these oscillations as well as the underlying physical mechanisms.