21 February 2011 Spin-controlled switching of lasing circular polarizations in (110)-oriented VCSELs
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We discuss high speed switching of lasing circular polarizations in VCSELs by optical spin injection. We conducted polarization- and time-resolved measurements of two consecutive lasing outputs from a (110)-InGaAs/GaAs VCSEL at 77 K with different time delays between the two optical excitations for alternately up- and down-spin electrons. 1-GHz switching of lasing circular polarizations has been demonstrated with taking advantage of the long electron spin relaxation time τs in (110)-QWs. Rate equation analysis closely reproduced the measured results and showed that shortening the carrier lifetime τc while preserving the long τs is a straightforward solution for faster switching since the residual unpolarized electrons limit the switching speed. Thus, we dry-etched the (110)-QWs into micro-posts to introduce the surface non-radiative recombination using ECR-RIE, and investigated the τc and τs. Spin-polarized carriers were optically excited in square posts with different sizes from 0.5 μm to 30 μm, and the time evolutions of two orthogonal circular polarization components of photoluminescence were measured by a streak camera. The long τ s (~1.3 ns) in the (110)-QW wafer is found to be preserved even when the sidewall boundaries with fast surface recombination are introduced and the τc is drastically shortened. The same rate equation analysis indicated that spin-controlled VCSELs with such (110)-QW micro-posts will exhibit faster switching thanks to the shortened τc and preserved long τs. In particular, 20-GHz switching is expected with 0.5-μm posts, although the threshold pulse energy per unit area becomes 2.9 times larger than that for 1-GHz switching without post structure.
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Nobuhide Yokota, Nobuhide Yokota, Kazuhiro Ikeda, Kazuhiro Ikeda, Shinji Koh, Shinji Koh, Hitoshi Kawaguchi, Hitoshi Kawaguchi, } "Spin-controlled switching of lasing circular polarizations in (110)-oriented VCSELs", Proc. SPIE 7937, Ultrafast Phenomena in Semiconductors and Nanostructure Materials XV, 79370T (21 February 2011); doi: 10.1117/12.873377; https://doi.org/10.1117/12.873377

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