Transverse and Polarization Mode Selection in VCSELs

We develop a mesoscopic model of semiconductor dynamics for
vertical-cavity surface-emitting lasers which allows us to
describe polarization and transverse mode dynamics simultaneously.
Within this model, we study the selection processes and the turn-on delay for the
switch-on of different transverse modes in gain-guided VCSELs. We consider
different active-region diameters, excitation conditions and current shapes.
Following the application of the current pulse, transverse modes become excited in
a quite definite sequence. After the turn-on, the VCSEL initially switches-on in
the fundamental transverse mode, but higher-order transverse modes
become excited later. In general, the results obtained are in
qualitative agreement with experiments reported recently. Finally, we discuss
the current shape dependence on the transverse mode selection at threshold.