Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

Q: Quantenoptik

Q 5: Halbleiter- und Festkörperlaser

Q 5.2: Vortrag

Montag, 24. März 2003, 11:15–11:30, E001

Polarization dynamics and low-frequency fluctuations in vertical-cavity surface-emitting lasers subjected to optical feedback — •T. Ackemann¹, M. Sondermann¹, H. Bohnet¹, A. Naumenko², and N.A. Loiko² — ¹Institut für Angewandte Physik, Westfälische Wilhelms–Universität Münster, Corrensstr. 2/4, 48149 Münster, Germany — ²Institute of Physics, Academy of Sciences of Belarus, Scaryna Prospekt 70, 220072 Minsk, Belarus

The polarization dynamics of vertical-cavity surface-emitting lasers (VCSELs) in the presence of isotropic optical feedback from a distant reflector is studied experimentally and theoretically. Low-frequency fluctuations (LFF) – sudden drops in power followed by a slow recovery process – are found to be a characteristic feature of the dynamics.

In the experiment, the existence of three types of LFF is demonstrated: First, both polarization modes are excited nearly equally and LFF events take place simultaneously. Second, if there is complete dominance of one polarization mode, this one undergoes single-mode LFF. In the intermediate case of a weak preference for one polarization mode, a LFF event in the dominant polarization mode might be accompanied by a burst of power in the normally depressed mode. The selection between the different scenarios is governed by the dichroism of the VCSEL.

For a theoretical description, the equations of motion of the so-called spin-flip model are generalized to take into account delayed feedback terms. The experimentally observed scenario can be qualitatively reproduced in numerical simulations, if spontaneous emission noise is taken into account.