27 February 2014 Coherent switching of polarization oscillations in vertical-cavity surface-emitting lasers
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Spin polarized lasers, especially spin polarized vertical-cavity surface-emitting lasers (VCSEL) provide improved performance when compared to conventional, purely charge-based lasers. Advantages of these spin-enhanced devices lie in their reduced laser threshold, increased emission intensity, amplification of spin information, chirp control and possibilities for ultrafast modulation due to their faster dynamics. Utilizing a commercially available conventional VCSEL and additional spin polarized optical pumping we are able to enhance the modulation dynamics of a conventional VCSEL with new spin effects. Our experiments show polarization oscillations in the spin-photon system that result in oscillations of the circular polarization of the VCSEL emission. The resulting polarization oscillations are of significantly higher frequency than the direct modulation bandwidth of the VCSEL and persist for durations longer than the spin lifetime in the active region. Simulations based on a rate-equation model show that with an improved VCSEL layout it should be possible to reach oscillation frequencies well above 100 GHz. Here, we show that with multiple optical spin polarized pulses these oscillations can be coherently excited, amplified and also stopped. Using this excitation scheme, polarization oscillations faster than the purely charge-based dynamics can be achieved with half-cycle to multi-cycle duration. Various influences of unpolarized electrical bias, optical excitation power and delay between pulses will be discussed both theoretically and experimentally. Additionally, we analyze the qualification of this new concept for ultrafast optical communication.
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Henning Höpfner, Henning Höpfner, Markus Lindemann, Markus Lindemann, Nils C. Gerhardt, Nils C. Gerhardt, Martin R. Hofmann, Martin R. Hofmann, "Coherent switching of polarization oscillations in vertical-cavity surface-emitting lasers", Proc. SPIE 9001, Vertical-Cavity Surface-Emitting Lasers XVIII, 90010G (27 February 2014); doi: 10.1117/12.2039196; https://doi.org/10.1117/12.2039196

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