Modes Distribution in Quantum-Cascade Vertical-Cavity Surface-Emitting Laser (VCSEL)

Performance of any semiconductor laser depends on an efficiency of mutual interaction between electrical carriers and an optical field. It concerns, in particular, performance of considered here new semiconductor lasers – the quantum-cascade vertical-cavity surface-emitting diode lasers (QC VCSELs). These lasers are anticipated to exhibit advantages of both the vertical-cavity surface-emitting diode lasers (VCSELs) and the unipolar quantum-cascade lasers (QCLs) without their undesirable drawbacks. The above interaction of radiation modes and electrical carriers is strictly connected with dimensions of the laser cavity and localization of an active region within it. Besides, the QC-VCSEL may take advantage of more than one active layer. Because of technological limitations, laser cavity should not be too large. For a typical active-area thickness of 2 micrometer, results of an optimization of a number and thicknesses of active layers to enhance an optical mode-carrier interaction leading to reduction of its lasing threshold are presented.