Continuous wave operation of injectorless quantum cascade lasers at low temperatures

A continuous wave operating quantum-cascade-laser without injector is presented. The core design was taken from a low-threshold pulsed staircase laser. The active zone of one sample was optimized for low threshold current densities, using 60 periods and a low doping of 2.4× 1010 cm-2 period. The second sample consists of 50 periods and a high doping of 6.3× 1010 cm-2 period. For the first (second) sample, the threshold current density at 77 K for continuous operation was measured with 0.13 (0.24) kA cm2 and maximum output power of 16.2 (22.7) mW was observed. Continuous operation was maintained up to 140 K for both lasers.