Continuous wave operation of injectorless quantum cascade lasersat 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 × 10 10 cm − 2 ∕ period . The second sample consists of 50 periods and a high doping of 6.3 × 10 10 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 ∕ cm 2 and maximum output power of 16.2 ( 22.7 ) mW was observed. Continuous operation was maintained up to 140 K for both lasers.