Continuous wave operation of a 9.3 <i>µ</i>m quantum cascade laser on a Peltier cooler

High average power quantum cascade lasers at 9.3 <i>µ</i>m using InP top cladding layers and both junction up and junction down mounting are presented. A 3 mm long, junction up mounted device emitted 54 mW average power at 30 °C and 11.5% duty cycle with a threshold current density of 3.72 kA/cm². A similar, but only 1.5 mm long device with high reflection coating on both facets was mounted junction down and tested at even higher duty cycles. At –27 °C, we achieved continuous wave operation with a threshold current density of 3.3 kA/cm².