This version is available at https://strathprints.strath.ac.uk/28917/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. We analyze the spin-induced circular polarization dynamics at the threshold of vertical-cavity surface-emitting lasers at room-temperature using a hybrid excitation combining electrically pumping without spin preference and spin-polarized optical injection. After a short pulse of spin-polarized excitation, fast oscillations of the circular polarization degree ͑CPD͒ are observed within the relaxation oscillations. A theoretical investigation of this behavior on the basis of a rate equation model shows that these fast oscillations of CPD could be suppressed by means of a reduction of the birefringence of the laser cavity. © 2010 American Institute of Physics. ͓doi:10.1063/1.3515855͔The study of spin-controlled optoelectronic devices has been a field of very active research over the last decade. Most studies concentrate on light emitting diodes ͑LEDs͒ with spin injection.1-5 Though polarization degrees up to 32% have been reported at room-temperature for spin-LEDs, 6 such values are too low for practical applications in communication technology. In addition, the LED dynamics is generally too slow to allow modulation at the high speed needed for data communication. In contrast, spincontrolled vertical-cavity surface-emitting lasers ͑VCSELs͒ can potentially be modulated at high speed and incorporate an intrinsic mechanism for the amplification of spin information due to their nonlinearity at threshold. 7,8 The implementation of first electrically pumped spin-VCSELs, 9,10 though only operated at low temperatures, demonstrates that spinVCSELs have enormous potential to become realistic spinoptoelectronic devices. However, conventional electrically pumped VCSELs are known to show complex polarization dynamics, including a predetermination for linearly polarized emission and irregular polarization switching behavior due to...

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Spin-polarized lasers offer new encouraging possibilities for future devices. We investigate the polarization dynamics of electrically pumped vertical-cavity surface-emitting lasers after additional spin injection at room temperature. We find that the circular polarization degree exhibits faster dynamics than the emitted light. Moreover the experimental results demonstrate a strongly damped ultrafast circular polarization oscillation due to spin injection with an oscillation frequency of approximately 11GHz depending on the birefringence in the VCSEL device. We compare our experimental results with theoretical calculations based on rate-equations. This allows us to predict undamped long persisting ultrafast polarization oscillations, which reveal the potential of spin-VCSELs for ultrafast modulation applications

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