Optically Pumped Spin-VCSELs: Toward High-Frequency Polarization Oscillations and Modulation

Spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) are known to support high-frequency continuous birefringence-induced oscillations whose frequency is not determined by the relaxation oscillation (RO) mechanism usually recognized in conventional laser diodes. However, this depends on the pumping condition as well as some key parameters. For example, the reported hybrid pumping consisting of standard electrical pumping and polarized light pulse excitation only results in damped high-frequency birefringence-induced oscillations. Here we focus on the optically pumped spin-VCSELs which have not been fully understood compared to those under hybrid pumping. We consider both periodic and continuous-wave (CW) regimes for exploiting high-frequency operation. In the periodic regime, the regions of period-one (P1) oscillations are identified via bifurcation diagrams and peak amplitude curves/maps, where the dependence on some key parameters is systematically studied. In the CW regime, we explore the high-frequency polarization modulation. In particular, double peak response curves are found when spin-VCSELs are pumped with a certain polarization degree and the RO frequency related peak in the frequency response curve is extremely sensitive to the variation of the polarization degree, which leads to rich modulation dynamics in spin-VCSELs. Additionally, the effects of the spin relaxation rate on the polarization modulation bandwidth are illustrated by using two-parameter bandwidth maps. These findings help us better understand the underlying high-frequency dynamics of the optically pumped spin-VCSELs.