Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 35: Semiconductor Laser
HL 35.13: Vortrag
Mittwoch, 25. März 2009, 17:30–17:45, BEY 154
Spin-relaxation measurements in VCSEL-structures at room temperature — •Hendrik Jähme1, Mingyuan Li1, Stephan Hövel1, Nils C. Gerhardt1, Martin R. Hofmann1, A. Kroner2, and R. Michalzik2 — 1Ruhr-Universität Bochum, Lehrstuhl für Photonik und Terahertztechnologie — 2Institut für Optoelektronik, Universität Ulm
We investigate the dynamic behaviour of optically induced electron spin-relaxation in a vertical-cavity surface-emitting laser (VCSEL). As the VCSEL emits perpendicularly to the active layer, it satisfies the Faraday-geometry required for the optical selection rules. A spin-amplification has been observed in such structures [1] raising interest in the utilisation of such devices for practical spintronic applications. We use a GaAs/AlGaAs-multi-quantum-well-laser and excite a spin-polarisation of electrons by pulsed optical pumping with circularly polarised light. Additionally the structure is pumped electrically to tune the rate of polarised carriers allowing an estimation of the spin-amplification [2]. A Stokes-polarimeter and a streak-camera are used to determine the degree of light polarisation and its dynamics.
An influence of the excitation on the emitted polarisation is observed. The dynamic measurements show relaxation-processes which are faster than the carrier-recombination dynamics. In this context we see a clear temporal separation between the pulses of right and left circularly polarised light on a low ps-timescale.
We thank the DFG for support within the SFB491
[1] S. Hövel et al, Spin controlled optically pumped vertical cavity surface emitting laser. Electronic Letters 41 (2005), No. 5
[2] S. Hövel et al, Optical spin manipulation of electrically pumped vertical-cavity surface-emitting lasers. APL 92, 041118 (2008)