Transverse mode selection and light-current characteristics in index-guided VCSELs

The recent rapid advances in the performance of vertical cavity surface emitting lasers (VCSELs) give significant impetus to identifying practical applications of these devices in, for example, optical data links and two-dimensional optical switching. In looking towards such applications serious consideration must be given to basic device performance characteristics and specifically to their operating efficiencies, threshold currents and transverse mode structures. Recent work has indicated the role of spatial hole-burning effects in determining both the transverse mode structure and the wall-plug efficiencies of gain-guided VCSELs. We show that the strength of the in-built transverse mode waveguide in index-guided VCSELs exerts a dramatic influence on the excitation of transverse modes. The influence is, in particular, revealed by calculated light-current characteristics of index guided VCSELs.