Transverse-Mode Characteristics of GaSb-Based VCSELs With Buried-Tunnel Junctions

We report the transverse-mode characteristics of GaSb-based vertical-cavity surface-emitting lasers (VCSELs) with buried-tunnel junctions (BTJs). The optical-index guiding in the devices is achieved by an effective refractive index step due to the presence of a laterally structured BTJ in the cavity. All lasing modes in VCSELs of different active diameters are experimentally measured. Then the experimental results are compared against the theoretical data for two different VCSEL designs emitting at 2.3 and 2.6 μm yielding a good agreement. The transverse-mode spacing between the excited modes is also determined and the results are compared with the theory. The far-field patterns ensure that devices with reasonable aperture diameters operate in single-fundamental LP₀₁ mode, showing that the devices are well-designed.