Threshold Characteristics of Quantum Dot Rolled-Up Microtube Lasers

We have investigated the threshold behavior of GaAs-based InAs self-organized quantum dot microtube lasers. The laser heterostructures were grown by molecular beam epitaxy and the devices were fabricated by standard optical lithography and etching techniques. Measurements have been made on microtube lasers of diameters 6, 9, and 12 . The spectral characteristics were measured by micro-photoluminescence and the data have been analyzed by considering the confinement and mode characteristics of the microtube. The threshold condition was derived after considering radiation, bending, and substrate losses associated with the devices. The threshold modal gain and excitation power are found to depend inversely on the microtube diameter.