SEMICONDUCTOR LASERS: Deep wells nearly double quantum-cascade-laser efficiency

摘要

Conventional quantum-cascade lasers (QCLs) have a core comprised of semiconductor quantum wells and barriers of fixed compositions; unfortunately, this construction causes carrier leakage in 4.5 to 5.5 (mu)m mid-IR-emitting QCL devices that manifests itself as a rapid decrease in slope efficiency and a rapid increase in threshold-current density with temperature due to the small energy differential (approximately 200 meV) between the upper lasing level and the top of the exit barrier in each of the 30 to 40 active regions of the device core. And even though devices with buried heterostructures can have front-facet wall-plug-efficiency (WPE) values of 12percent at room temperature, those devices are highly temperature sensitive and as a result are far from achieving their theoretical 28percent WPE values.