High-performance injectorless quantum cascade lasers emitting below 6 μm

An injectorless quantum cascade laser emitting around 5.7 μm with more than 1 W of output power and a wall-plug efficiency of 3.6% at room temperature in pulsed operation is presented. The active region of the device is a design that picked up the idea of the four-alloy structure, which has already lead to very low threshold current densities. The pulsed threshold current densities were measured as low as 1.1 kA/cm2 at room temperature for an as-cleaved 3.6 mm long device, and 0.93 kA/cm2 for a high-reflection-coated 4 mm long device.