Optimizing facet coating of quantum cascade lasers for low power consumption

Typical high power consumption (similar to 10 W) of mid-infrared quantum cascade lasers (QCLs) has been a serious limitation for applications in battery powered systems. A partial high-reflection (PHR) coating technique is introduced for power downscaling with shorter cavity lengths. The PHR coating consists of a double layer dielectric of SiO2 and Ge. With this technique, a 4.6 mu m QCL with an ultra low threshold power consumption of less than a watt (0.83 W) is demonstrated in room temperature continuous wave operation. At 25 degrees C, the maximum output power and wall plug efficiency are 192 mW and 8.6%, respectively. (C) 2011 American Institute of Physics. [doi:10.1063/1.3553863]