Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 39: Posters II (Topological insulators; Graphene; Spintronics and spin physics; Quantum information science)
HL 39.35: Poster
Tuesday, March 17, 2015, 14:00–20:00, Poster F
Controlling the frequency of ultra-fast polarization oscillations in Spin-VCSELs — •Markus Lindemann1, Henning Höpfner1, Nils C. Gerhardt1, Martin R. Hofmann1, Tobias Pusch2, and Rainer Michalzik2 — 1Photonics and Terahertz Technology, Ruhr-University Bochum, 44780 Bochum, Germany — 2Institute of Optoelectronics, Ulm University, 89081 Ulm, Germany
Spin-polarized optoelectronic devices offer several advantages in comparison to their conventional counterparts. One of these benefits is the possibility of polarization manipulation, as the optical polarization degree is connected with the carrier spin via the optical selection rules. The modulation speed of the spin is fast in comparison to the modulation frequency of the laser's intensity, which is limited by the dynamics of the carrier-photon system. Therefore the polarization modulation bandwidth generally exceeds the direct intensity modulation bandwidth. Due to cavity anisotropies the VCSEL bears two orthogonal linear polarized modes. In case of spin-injection, both modes evolve lasing operation simultaneously. This leads to an oscillation in the circular polarization degree. By switching this oscillation on and off with spin injection, short polarization bursts can be generated (H. Höpfner et al, Appl. Phys. Lett., 104, 022409 (2014)). The frequency of this oscillation and therefore the minimal width of the polarization bursts depend on the frequency distance of the two VCSEL modes exclusively. This is determined by the birefringence of the lasing material. We investigate optimization strategies to reach very high oscillation frequencies by manipulating the birefringence via mechanical strain.