Spatio-temporal emission dynamics of VCSELs: modal competition in the turn-on behavior

We present 2D-spatially and temporally resolved measurements of the emission of selectively oxidized state- of-the-art VCSELs of intermediate aperture sizes, showing their rich modal, polarization, spectral, and spatial dynamics. For the characterization of the repetitive dynamics we performed experiments with a technique we developed called TRIDA (Temporally Resolved Imaging by Differential Analysis) providing a temporal resolution down to 10 ps. From the temporal evolution of the near-field emission we provide a comprehensive overview of the phenomena in the turn-on dynamics. The evolution of the spatial intensity distribution of the transverse modes over a range of some nanoseconds is presented and discussed. Complementary, we have taken single-shot images of the near-field emission of 3 ns short pulses in order to characterize the nonrepetitive part of the dynamics and to get a deeper understanding of the dynamical processes arising from the interaction of transverse modes in the turn-on process. We find strong variations in the intensity distribution among the transverse modes and the polarization directions, indicating the onset of spatio-temporal chaos. A correlation analysis for the modal intensities is performed showing the influence of the competition for the available spatial and spectral gain.